Organic solid-state semiconductor laser and method for reducing peak width of emission spectrum of organic electroluminescent element

Abstract

An organic solid-state semiconductor laser having a small emission spectrum peak width is characterized by being provided with: a hole injection unit; an electron injection unit; a light-emitting layer that recombines holes and electrons and emits light; and an optical resonator that propagates the emitted light within the light-emitting layer, the optical resonator having a hole blocking layer adjacent to the light-emitting layer on the electron injection section side of the light-emitting layer, or having an electron blocking layer adjacent to the light-emitting layer on the hole injection section side of the light-emitting layer.

Description

Technical Field

[0001] The present invention relates to a method for reducing the peak width of the emission spectrum of an organic solid semiconductor laser and an organic electroluminescent element using an organic compound as a laser oscillation material. Background Art

[0002] Compared to inorganic semiconductor lasers, organic solid-state semiconductor lasers, which use organic compounds as laser oscillation materials, have wider wavelength variability, are easier to impart flexibility, and can be manufactured at lower costs. Therefore, they are expected to be applied in various fields utilizing laser light, and research and development towards their practical application is actively underway.

[0003] For example, Patent Document 1 describes the use of BSBCz (4-4'-bis[(N-carbazole)styrene]biphenyl) as a laser oscillation material to produce an organic solid-state semiconductor laser and confirm laser oscillation. Figure 19 As shown, the organic solid semiconductor laser produced here is formed by stacking an ITO cathode 101, a light-emitting layer 102 containing BSBCz, and an anode 103 composed of a stacked structure of MoO3 layer / Ag layer / Al layer, and the light-emitting layer 102 is formed with a thickness of 210 nm.

[0004] Previous technical literature

[0005] Patent Literature

[0006] Patent Document 1: WO2018 / 147470 Summary of the Invention

[0007] Technical issues to be solved by the invention

[0008] As described above, various organic solid-state semiconductor lasers having a light-emitting layer containing BSBCz or the like formed between an anode and a cathode have been proposed. However, there is still a need to develop an organic solid-state semiconductor laser or organic electroluminescent element with further improved performance compared to conventional devices. For example, it is desirable to provide an organic solid-state semiconductor laser that further improves laser efficiency and monochromaticity or that can be driven at a lower voltage.

[0009] Therefore, in order to solve such conventional technical problems, the present inventors have conducted research with the aim of providing an organic solid-state semiconductor laser or an organic electroluminescent element having a small peak width of an emission spectrum (light intensity distribution with respect to wavelength).

[0010] Means for solving technical problems

[0011] To solve the above-mentioned problems, the present inventors have conducted intensive research and have found a structure in which the peak width of the emission spectrum is significantly narrowed. The present invention has been proposed based on these findings and specifically has the following structure.

[0012] [1] A method for reducing the full width at half maximum (FWHM) of the emission wavelength peak of the emission spectrum of an organic electroluminescent element, wherein:

[0013] The organic electroluminescent element comprises:

[0014] a hole injection portion for injecting holes;

[0015] an electron injection unit for injecting electrons; and

[0016] The light-emitting layer allows holes and electrons to recombine and emit light.

[0017] The light generated in the light-emitting layer propagates in the lateral direction of the light-emitting layer.

[0018] The method is characterized in that a recombination concentration portion is provided along the lateral direction of the light emitting layer.

[0019] Here, the recombination concentrated area is a region where recombination of holes and electrons occurs in a concentrated manner and the exciton density becomes high (exciton high density region). The position of the recombination concentrated area can be determined by, for example, simulation of the exciton density distribution.

[0020] [2] A method for reducing the full width at half maximum (FWHM) of the emission wavelength peak of the emission spectrum of an organic electroluminescent element, wherein:

[0021] The organic electroluminescent element comprises:

[0022] a hole injection portion for injecting holes;

[0023] an electron injection unit for injecting electrons; and

[0024] The light-emitting layer is disposed between the hole injection portion and the electron injection portion, and allows holes and electrons to recombine to emit light.

[0025] The light generated in the light-emitting layer propagates in the lateral direction of the light-emitting layer.

[0026] The method is characterized in that

[0027] When the side of the light-emitting layer that becomes the exciton high density region is the electron injection portion side, the hole blocking layer is provided between the light-emitting layer and the electron injection portion and adjacent to the light-emitting layer.

[0028] When the side of the light-emitting layer that becomes the exciton high density region is the hole injection portion side, the electron blocking layer is provided between the light-emitting layer and the hole injection portion and adjacent to the light-emitting layer.

[0029] [3] The method according to [1] or [2], wherein

[0030] A low refractive index layer having a lower refractive index than that of the light-emitting layer is provided between the light-emitting layer and the hole injection portion and between the light-emitting layer and the electron injection portion.

[0031] [4] The method according to any one of [1] to [3], wherein

[0032] The position of the exciton high density region in the light-emitting layer is determined by simulating the exciton density distribution in the light-emitting layer.

[0033] [5] The method according to any one of [2] to [4], wherein

[0034] The side of the light-emitting layer that becomes the exciton high density region is the electron injection portion side, and the hole blocking layer is provided between the light-emitting layer and the electron injection portion and adjacent to the light-emitting layer.

[0035] [6] The method according to [5], characterized in that

[0036] The absolute value of the HOMO energy of the hole blocking layer is greater than the absolute value of the HOMO energy of the light emitting layer (eg, 0.1 eV or greater, eg, 0.2 eV or greater, eg, 0.4 eV or greater).

[0037] [7] The method according to [5] or [6], characterized in that

[0038] The hole mobility of the hole blocking layer is reduced.

[0039] [8] The method according to any one of [5] to [7], characterized in that

[0040] One or more layers (for example, an electron transport layer) are provided between the hole blocking layer and the electron injection portion.

[0041] [9] The method according to [8], characterized in that

[0042] The electron mobility of the electron transport layer is reduced.

[0043]

[10] The method according to [8] or [9], characterized in that

[0044] The absolute value of the HOMO energy of the electron transport layer is set to be greater than the absolute value of the HOMO energy of the light emitting layer by 0.1 eV or more (for example, greater by 0.2 eV or more).

[0045]

[11] The method according to any one of [5] to

[10] , characterized in that

[0046] The total thickness of the layers between the light emitting layer and the electron injection portion is increased.

[0047]

[12] The method according to any one of [5] to

[11] , characterized in that

[0048] The total thickness of one or more layers between the light-emitting layer and the electron injection portion is at least twice (eg, 2.5 or more, for example, 3 or more) greater than the total thickness of one or more layers between the light-emitting layer and the hole injection portion.

[0049]

[13] The method according to any one of [5] to

[12] , characterized in that

[0050] The refractive index of a layer located between the light-emitting layer and the electron injection portion is reduced.

[0051]

[14] The method according to any one of [5] to

[13] , characterized in that

[0052] The refractive index of the light emitting layer is increased.

[0053]

[15] The method according to any one of [5] to

[14] , characterized in that

[0054] The hole mobility of the light-emitting layer is improved.

[0055]

[16] The method according to any one of [5] to

[15] , characterized in that

[0056] The light emitting layer is thinned.

[0057]

[17] The method according to any one of [5] to

[16] , characterized in that

[0058] The hole mobility of the layer located between the hole injection portion and the light emitting layer is improved.

[0059]

[18] The method according to any one of [2] to [4], wherein

[0060] The side of the light-emitting layer that becomes the exciton high density region is the hole injection portion side, and the electron blocking layer is provided between the light-emitting layer and the hole injection portion and adjacent to the light-emitting layer.

[0061]

[19] The method according to

[18] , characterized in that

[0062] The absolute value of the LUMO energy of the electron blocking layer is smaller than the absolute value of the LUMO energy of the light-emitting layer by 0.1 eV or more (eg, 0.2 eV or more, for example, 0.4 eV or more).

[0063]

[20] The method according to

[18] or

[19] , characterized in that

[0064] The electron mobility of the electron blocking layer is reduced.

[0065]

[21] The method according to any one of

[18] to

[20] , characterized in that

[0066] A hole transport layer is provided between the electron blocking layer and the hole injection portion.

[0067]

[22] The method according to any one of

[18] to

[21] , characterized in that

[0068] The hole mobility of the hole transport layer is reduced.

[0069]

[23] The method according to any one of

[18] to

[22] , characterized in that

[0070] The absolute value of the LUMO energy of the hole transport layer is smaller than the absolute value of the LUMO energy of the light emitting layer by 0.1 eV or more (for example, smaller by 0.2 eV or more).

[0071]

[24] The method according to any one of

[18] to

[23] , characterized in that

[0072] The total thickness of the layers between the light-emitting layer and the hole injection portion is increased.

[0073]

[25] The method according to any one of

[18] to

[24] , characterized in that

[0074] The total thickness of one or more layers between the light-emitting layer and the electron injection portion is at least twice (eg, 2.5 or more, for example, 3 or more) greater than the total thickness of one or more layers between the light-emitting layer and the hole injection portion.

[0075]

[26] The method according to any one of

[18] to

[25] , characterized in that

[0076] The refractive index of a layer located between the light-emitting layer and the hole injection portion is reduced.

[0077]

[27] The method according to any one of

[18] to

[26] , characterized in that

[0078] The refractive index of the light emitting layer is increased.

[0079]

[28] The method according to any one of

[18] to

[27] , characterized in that

[0080] The electron mobility of the light-emitting layer is improved.

[0081]

[29] The method according to any one of

[18] to

[28] , characterized in that

[0082] The light emitting layer is thinned.

[0083]

[30] The method according to any one of

[18] to

[29] , characterized in that

[0084] The electron mobility of the layer located between the electron injection portion and the light emitting layer is improved.

[0085]

[31] The method according to any one of [1] to

[30] , characterized in that

[0086] The full width at half maximum (FWHM) of the emission angle peak is set to 10 degrees or less (eg, 7 degrees or less, 5 degrees or less, 4 degrees or less, 3 degrees or less, 2 degrees or less, 1 degree or less).

[0087]

[32] The method according to any one of [1] to

[31] , characterized in that

[0088] The full width at half maximum (FWHM) of the emission wavelength peak is set to 10 nm or less (eg, 7 nm or less, 5 nm or less, 4 nm or less, 3 nm or less, 2 nm or less, 1 nm or less).

[0089]

[33] The method according to any one of [1] to

[32] , wherein

[0090] The electron injection portion has a structure in which a dielectric, a metal, and a dielectric are stacked in this order (DMD structure).

[0091]

[34] The method according to any one of [1] to

[33] , characterized in that

[0092] The invention relates to a design method of an organic electroluminescent element.

[0093]

[35] The method according to any one of [1] to

[34] , characterized in that

[0094] The organic electroluminescent element further includes an optical resonator that propagates emitted light within the light-emitting layer, and the organic electroluminescent element oscillates laser light.

[0095]

[36] The method according to

[35] , wherein

[0096] The optical resonator has a diffraction grating.

[0097]

[37] The method according to

[36] , wherein

[0098] The hole blocking layer or the electron blocking layer is formed along a flat interface of the light emitting layer.

[0099]

[38] The method according to

[36] or

[37] , wherein

[0100] The diffraction grating is disposed between the high exciton density region and the hole injection portion or between the high exciton density region and the electron injection portion.

[0101]

[39] The method according to

[38] , wherein

[0102] When a diffraction grating is provided between the exciton high density region and the hole injection portion, the hole blocking layer is provided between the light emitting layer and the electron injection portion and adjacent to the light emitting layer.

[0103] When a diffraction grating is provided between the exciton high density region and the electron injection portion, the electron blocking layer is provided between the light emitting layer and the hole injection portion and adjacent to the light emitting layer.

[0104]

[40] The method according to any one of

[35] to

[39] , characterized in that

[0105] It is a design method for organic solid-state semiconductor lasers.

[0106]

[41] A device having an organic electroluminescent element manufactured by implementing the method described in any one of [1] to

[40] and having a reduced full width at half maximum (FWHM) of a light emission wavelength peak of a light emission spectrum.

[0107]

[42] A method for manufacturing a device having an organic electroluminescent element with a reduced full width at half maximum (FWHM) of a light emission wavelength peak of a light emission spectrum, the method comprising:

[0108] The method comprises the step of manufacturing an organic electroluminescent element by the method described in any one of [1] to

[40] .

[0109]

[43] An organic electroluminescent element manufactured by implementing the method described in any one of [1] to

[40] and having a reduced full width at half maximum (FWHM) of a light emission wavelength peak of a light emission spectrum.

[0110]

[44] An organic solid-state semiconductor laser manufactured by implementing the method described in any one of

[35] to

[40] and having a reduced full width at half maximum (FWHM) of a light emission wavelength peak of a light emission spectrum.

[0111]

[45] A method for adjusting at least one of the thickness and the refractive index of a first spacer layer of an organic electroluminescent element,

[0112] The organic electroluminescent element comprises:

[0113] a hole injection portion for injecting holes;

[0114] an electron injection unit for injecting electrons;

[0115] a light-emitting layer disposed between the hole injection portion and the electron injection portion, and causing holes and electrons to recombine to emit light; and

[0116] a first spacer layer disposed between the light-emitting layer and the electron injection portion;

[0117] The method is characterized in that at least one of the thickness and the refractive index of the first spacer layer is adjusted using an absorption model.

[0118]

[46] The method according to

[45] , wherein

[0119] At least one of the thickness and the refractive index of the first spacer layer of the organic electroluminescent element is adjusted using an absorption model for a laminate sample in which a light-emitting layer, a first spacer layer, and an electron injection portion are sequentially laminated.

[0120]

[47] The method according to

[46] , wherein

[0121] The laminate sample further includes an optical resonator, and at least one of a thickness and a refractive index of a first spacer layer of the organic electroluminescent element is adjusted using an absorption model for the laminate sample.

[0122]

[48] ​​The method according to

[46] or

[47] , wherein

[0123] For the laminate sample, the relationship between the thickness of the first spacer layer and the absorption coefficient of the laminate sample is calculated using an absorption model, and the thickness of the first spacer layer of the organic electroluminescent element is selected from the thickness range of the first spacer layer whose absorption coefficient is below a set reference threshold in this relationship.

[0124]

[49] The method according to

[46] or

[47] , wherein

[0125] For the stacked body sample, the relationship between the refractive index of the first spacer layer and the absorption coefficient of the stacked body sample is calculated by an absorption model, and the refractive index of the first spacer layer of the organic electroluminescent element is selected from the refractive index range of the first spacer layer whose absorption coefficient is below the set reference threshold in this relationship.

[0126]

[50] A method for adjusting at least one of the thickness and refractive index of a second spacer layer of an organic electroluminescent element,

[0127] The organic electroluminescent element comprises:

[0128] a hole injection portion for injecting holes;

[0129] an electron injection unit for injecting electrons;

[0130] a light-emitting layer disposed between the hole injection portion and the electron injection portion, and causing holes and electrons to recombine to emit light; and

[0131] The second spacer layer is disposed between the light-emitting layer and the hole injection portion.

[0132] The method is characterized in that at least one of the thickness and the refractive index of the second spacer layer is adjusted using an absorption model.

[0133]

[51] The method according to

[50] , wherein

[0134] At least one of the thickness and the refractive index of the second spacer layer of the organic electroluminescent element is adjusted using an absorption model for a laminate sample in which a hole injection portion, a second spacer layer, and a light-emitting layer are sequentially laminated.

[0135]

[52] The method according to

[51] , wherein

[0136] The laminate sample further includes an optical resonator, and at least one of a thickness and a refractive index of a second spacer layer of the organic electroluminescent element is adjusted using an absorption model for the laminate sample.

[0137]

[53] The method according to

[51] or

[52] , wherein

[0138] For the laminate sample, the relationship between the thickness of the second spacer layer and the absorption coefficient of the laminate sample is calculated through an absorption model, and the thickness of the second spacer layer of the organic electroluminescent element is selected from the thickness range of the second spacer layer whose absorption coefficient is below the set reference threshold in this relationship.

[0139]

[54] The method according to

[51] or

[52] , wherein

[0140] For the stacked body sample, the relationship between the refractive index of the second spacer layer and the absorption coefficient of the stacked body sample is calculated by an absorption model, and the refractive index of the second spacer layer of the organic electroluminescent element is selected from the refractive index range of the second spacer layer whose absorption coefficient is below the set reference threshold in this relationship.

[0141]

[55] An organic electroluminescent element produced by implementing the method described in any one of

[45] to

[54] .

[0142]

[56] An organic solid-state semiconductor laser manufactured by implementing the method described in any one of

[45] to

[54] .

[0143]

[57] An organic solid-state semiconductor laser, characterized by comprising:

[0144] a hole injection portion for injecting holes;

[0145] an electron injection unit for injecting electrons;

[0146] a light-emitting layer disposed between the hole injection portion and the electron injection portion, and causing holes and electrons to recombine to emit light; and

[0147] Optical resonator, which allows the emitted light to propagate within the light-emitting layer,

[0148] A hole blocking layer is provided on the electron injection portion side of the light-emitting layer so as to be adjacent to the light-emitting layer, or an electron blocking layer is provided on the hole injection portion side of the light-emitting layer so as to be adjacent to the light-emitting layer.

[0149]

[58] The organic solid semiconductor laser according to any one of

[44] ,

[56] or

[57] , characterized in that

[0150] A hole blocking layer is provided on the electron injection portion side of the light-emitting layer so as to be adjacent to the light-emitting layer.

[0151]

[59] The organic solid semiconductor laser according to

[58] , characterized in that

[0152] The absolute value of the HOMO (Highest Occupied Molecular Orbital) energy of the hole blocking layer is greater than the absolute value of the HOMO energy of the light emitting layer by 0.1 eV or more.

[0153]

[60] The organic solid semiconductor laser according to

[58] , characterized in that

[0154] An absolute value of the HOMO energy of the hole blocking layer is greater than an absolute value of the HOMO energy of the light emitting layer by 0.2 eV or more.

[0155]

[61] The organic solid semiconductor laser according to

[58] , characterized in that

[0156] An absolute value of the HOMO energy of the hole blocking layer is greater than an absolute value of the HOMO energy of the light emitting layer by 0.4 eV or more.

[0157]

[62] The organic solid semiconductor laser according to any one of

[58] to

[61] , characterized in that

[0158] The hole blocking layer is made of a material having low hole mobility.

[0159]

[63] The organic solid semiconductor laser according to any one of

[58] to

[61] , characterized in that

[0160] The hole blocking layer is made of a material having a hole mobility equal to or lower than that of TPBi ([1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene]) (for example, equal to or lower than that of T2T (2,4,6-tris([1,1′-biphenyl]-3-yl))-1,3,5-triazine)).

[0161]

[64] The organic solid semiconductor laser according to any one of

[58] to

[63] , characterized in that

[0162] The thickness of the hole blocking layer is greater than 1 nm (eg, greater than 3 nm, eg, greater than 5 nm, eg, greater than 8 nm, eg, less than 80 nm, eg, less than 30 nm, eg, less than 15 nm).

[0163]

[65] The organic solid semiconductor laser according to any one of

[58] to

[64] , characterized in that

[0164] An electron transport layer is further provided between the hole blocking layer and the electron injection portion.

[0165]

[66] The organic solid semiconductor laser according to

[65] , characterized in that

[0166] The thickness of the electron transport layer is greater than or equal to 10 nm (eg, greater than or equal to 20 nm, eg, greater than or equal to 40 nm, eg, greater than or equal to 60 nm, eg, less than or equal to 100 nm, eg, less than or equal to 80 nm).

[0167]

[67] The organic solid semiconductor laser according to

[65] or

[66] , characterized in that

[0168] The electron transport layer is composed of a material having an electron mobility equal to or less than that of TPBi ([1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene]).

[0169]

[68] The organic solid semiconductor laser according to any one of

[65] to

[67] , characterized in that

[0170] The absolute value of the HOMO energy of the electron transport layer is greater than the absolute value of the HOMO energy of the light emitting layer by 0.1 eV or more (for example, greater by 0.2 eV or more).

[0171]

[69] The organic solid semiconductor laser according to any one of

[58] to

[68] , characterized in that

[0172] The total thickness of one or more layers provided between the light-emitting layer and the electron injection portion is at least twice (eg, 2.5 times, for example, 3 times) greater than the total thickness of one or more layers provided between the light-emitting layer and the hole injection portion.

[0173]

[70] The organic solid semiconductor laser according to any one of

[58] to

[69] , characterized in that

[0174] The light-emitting layer is composed of a material having a hole mobility equal to or higher than that of BSBCz (4-4'-bis[(N-carbazole)styrene]biphenyl).

[0175]

[71] The organic solid semiconductor laser according to any one of

[58] to

[70] , characterized in that

[0176] The light emitting layer includes a laser oscillation material and a dopant material.

[0177]

[72] The organic solid semiconductor laser according to

[71] , characterized in that

[0178] The dopant material includes a light-emitting material.

[0179]

[73] The organic solid semiconductor laser according to

[72] , characterized in that

[0180] The luminescent material is a compound selected from the group consisting of fluorene molecules, styrene-benzene molecules, carbazole-styrene biphenyl compounds, TADF materials (thermally activated delayed fluorescence materials), star polymers, polyfluorene, phenylene vinylene polymers, and ladder polymers.

[0181]

[74] The organic solid semiconductor laser according to any one of

[71] to

[73] , characterized in that

[0182] The dopant material includes a triplet quencher.

[0183]

[75] The organic solid semiconductor laser according to

[74] , characterized in that

[0184] The triplet extinction agent is a compound containing an anthracene ring.

[0185]

[76] The organic solid semiconductor laser according to

[75] , characterized in that

[0186] The anthracene ring-containing compound is the following compound.

[0187] [Chemical Formula 1]

[0188]

[0189]

[77] The organic solid semiconductor laser according to any one of

[58] to

[76] , characterized in that

[0190] A layer composed of a material having a hole mobility equal to or higher than that of HATCN ([dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile]) is provided between the hole injection portion and the light-emitting layer.

[0191]

[78] The organic solid semiconductor laser according to any one of

[44] ,

[56] , and

[57] , characterized in that:

[0192] An electron blocking layer is provided on the hole injection portion side of the light-emitting layer so as to be adjacent to the light-emitting layer.

[0193]

[79] The organic solid semiconductor laser according to

[78] , characterized in that

[0194] The absolute value of the energy of LUMO (Lowest Unoccupied Molecular Orbital) of the electron blocking layer is smaller than the absolute value of the LUMO energy of the light-emitting layer by 0.1 eV or more.

[0195]

[80] The organic solid semiconductor laser according to

[78] , characterized in that

[0196] An absolute value of the LUMO energy of the electron blocking layer is smaller than an absolute value of the LUMO energy of the light-emitting layer by 0.2 eV or more.

[0197]

[81] The organic solid semiconductor laser according to

[78] , characterized in that

[0198] An absolute value of the LUMO energy of the electron blocking layer is smaller than an absolute value of the LUMO energy of the light-emitting layer by 0.4 eV or more.

[0199]

[82] The organic solid semiconductor laser according to any one of

[78] to

[81] , characterized in that

[0200] The electron blocking layer is made of a material with low electron mobility.

[0201]

[83] The organic solid semiconductor laser according to any one of

[78] to

[82] , characterized in that

[0202] The electron blocking layer is made of a material with low electron mobility.

[0203]

[84] The organic solid semiconductor laser according to any one of

[78] to

[83] , characterized in that

[0204] The thickness of the electron blocking layer is greater than 1 nm (eg, greater than 3 nm, eg, greater than 5 nm, eg, greater than 8 nm, eg, less than 80 nm, eg, less than 30 nm, eg, less than 15 nm).

[0205]

[85] The organic solid semiconductor laser according to any one of

[78] to

[84] , characterized in that

[0206] A hole transport layer is further provided between the electron blocking layer and the hole injection portion.

[0207]

[86] The organic solid semiconductor laser according to

[85] , characterized in that

[0208] The thickness of the hole transport layer is greater than or equal to 10 nm (eg, greater than or equal to 20 nm, eg, greater than or equal to 40 nm, eg, greater than or equal to 60 nm, eg, less than or equal to 100 nm, eg, less than or equal to 80 nm).

[0209]

[87] The organic solid semiconductor laser according to

[85] or

[86] , characterized in that

[0210] The hole transport layer is made of a material having a hole mobility equal to or less than that of HATCN ([dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile]).

[0211]

[88] The organic solid semiconductor laser according to any one of

[85] to

[87] , characterized in that

[0212] The absolute value of the LUMO energy of the hole transport layer is smaller than the absolute value of the LUMO energy of the light emitting layer by 0.1 eV or more (for example, smaller by 0.2 eV or more).

[0213]

[89] The organic solid semiconductor laser according to any one of

[78] to

[88] , characterized in that

[0214] The total thickness of one or more layers provided between the light-emitting layer and the hole injection portion is at least twice (eg, 2.5 times, for example, 3 times) greater than the total thickness of one or more layers provided between the light-emitting layer and the electron injection portion.

[0215]

[90] The organic solid semiconductor laser according to any one of

[56] to

[89] , characterized in that

[0216] The refractive index of a layer provided between the light-emitting layer and the electron injection portion is smaller than the refractive index of the light-emitting layer.

[0217]

[91] The organic solid semiconductor laser according to any one of

[56] to

[90] , characterized in that

[0218] The refractive index of the layer provided between the light-emitting layer and the hole injection portion is smaller than the refractive index of the light-emitting layer.

[0219]

[92] The organic solid semiconductor laser according to any one of

[44] ,

[56] to

[91] , characterized in that:

[0220] The thickness of the light-emitting layer is greater than or equal to 10 nm and less than 200 nm.

[0221]

[93] The organic solid semiconductor laser according to any one of

[44] ,

[56] to

[92] , characterized in that:

[0222] The hole mobility of the light-emitting layer is more than 10 times greater than the electron mobility.

[0223]

[94] The organic solid semiconductor laser according to any one of

[44] ,

[56] to

[93] , characterized in that:

[0224] The light-emitting layer consists only of a light-emitting material.

[0225]

[95] The organic solid semiconductor laser according to any one of

[44] ,

[56] to

[94] , characterized in that:

[0226] The light-emitting layer is a layer obtained by doping a host material with a light-emitting material.

[0227]

[96] The organic solid semiconductor laser according to any one of

[44] ,

[56] to

[95] , characterized in that:

[0228] The hole injection part is an electrode.

[0229]

[97] The organic solid semiconductor laser according to any one of

[44] ,

[56] to

[96] , characterized in that:

[0230] At least one of the electron injection portion and the hole injection portion is an electrode having a visible light transmittance of 10% or more (eg, 50% or more, eg, 80% or more, eg, 90% or more).

[0231]

[98] The organic solid semiconductor laser according to any one of

[43] ,

[53] to

[94] , characterized in that:

[0232] The hole injection portion is made of ITO (indium tin oxide).

[0233]

[99] The organic solid semiconductor laser according to any one of

[44] ,

[56] to

[98] , characterized in that:

[0234] The electron injection part is an electrode.

[0235]

[100] The organic solid semiconductor laser according to any one of

[44] ,

[56] to

[99] , characterized in that:

[0236] The electron injection part is a metal electrode.

[0237]

[101] The organic solid semiconductor laser according to any one of

[44] ,

[56] to

[100] , characterized in that

[0238] The electron injection portion has a structure in which a dielectric, a metal, and a dielectric are stacked in this order.

[0239]

[102] The organic solid semiconductor laser according to

[101] , characterized in that

[0240] The metal is silver (Ag).

[0241]

[103] The organic solid semiconductor laser according to

[101] or

[102] , characterized in that

[0242] The dielectric is molybdenum trioxide (MoO3).

[0243]

[104] The organic solid semiconductor laser according to any one of

[56] to

[103] , characterized in that

[0244] It is a surface emitting type.

[0245]

[105] The organic solid semiconductor laser according to any one of

[56] to

[100] , wherein

[0246] The light generated in the light-emitting layer propagates in a lateral direction of the light-emitting layer.

[0247]

[106] The method according to

[105] , wherein

[0248] A low refractive index layer having a lower refractive index than that of the light-emitting layer is provided between the light-emitting layer and the hole injection portion and between the light-emitting layer and the electron injection portion.

[0249]

[107] The organic solid semiconductor laser according to any one of

[57] to

[106] , wherein

[0250] The optical resonator has a diffraction grating.

[0251]

[108] The organic solid semiconductor laser according to

[107] , wherein

[0252] The hole blocking layer or the electron blocking layer is formed along a flat interface of the light emitting layer.

[0253]

[109] The organic solid semiconductor laser according to

[107] or

[108] , wherein

[0254] The base end of the diffraction grating is arranged at the interface on the hole injection side of the light-emitting layer or at a position closer to the hole injection side than the interface. The hole blocking layer is arranged between the light-emitting layer and the electron injection part and adjacent to the light-emitting layer.

[0255]

[110] The organic solid semiconductor laser according to

[107] or

[108] , wherein

[0256] The base end of the diffraction grating is arranged at the interface on the electron injection side of the light-emitting layer or at a position closer to the electron injection side than the interface. The electron blocking layer is arranged between the light-emitting layer and the hole injection part and adjacent to the light-emitting layer.

[0257]

[111] The organic solid semiconductor laser according to any one of

[56] to

[104] and

[107] to

[110] , characterized in that

[0258] It is a top-emitting type.

[0259]

[112] The organic solid semiconductor laser according to any one of

[56] to

[104] and

[107] to

[111] , characterized in that

[0260] It is a bottom-emitting type.

[0261]

[113] The organic solid semiconductor laser according to any one of

[56] to

[104] and

[107] to

[112] , characterized in that

[0262] It is a dual-emitter type.

[0263]

[114] The organic solid semiconductor laser according to any one of

[56] to

[110] , characterized in that

[0264] It is an end-emitting type.

[0265]

[115] A program that implements the method described in any one of [1] to

[40] and

[45] to

[54] .

[0266] The above-mentioned "DMD structure" is an abbreviation of a dielectric-metal-dielectric structure. In the present invention, an electrode that utilizes interference of a stacked structure can be used. As a DMD structure, in addition to MoO3 / Ag / MoO3 used in the embodiment, ITO / Ag / ITO, ZnS / Ag / ZnS, ZnO / Ag / ZnO, InZnSnO / Ag / InZnSnO, ITO / Ag / WO3, ZnO / Ag / WO3, WO3 / Ag / WO3, etc. can also be used. In one embodiment of the present invention, a DMD structure is used as an electron injection unit. A component having a DMD structure can be manufactured, for example, by a process of forming the DMD structure on a silicon substrate.

[0267] By forming the electron injection portion from a material with high transmittance, a top-emitting organic electroluminescent element and an organic solid-state semiconductor laser can be provided. In one embodiment of the present invention, the electron injection portion is set to a DMD structure with high transmittance, a thin Ag layer (for example, a thickness of less than 40 nm, for example, 5 to 30 nm, for example, 12 to 25 nm). Furthermore, by forming the hole injection portion from a material with high transmittance, a bottom-emitting organic electroluminescent element and an organic solid-state semiconductor laser can be provided. In one embodiment of the present invention, the hole injection portion is set to an ITO layer. Furthermore, by forming both the electron injection portion and the hole injection portion from materials with high transmittance, a dual-emission (transparent) organic electroluminescent element and an organic solid-state semiconductor laser can also be provided.

[0268] Effects of the Invention

[0269] According to the present invention, an organic solid-state semiconductor laser or an organic electroluminescent element having a small peak width of an emission spectrum can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0270] Figure 1 This is a structural example showing a first embodiment of the organic solid-state semiconductor laser of the present invention. Figure 1 (a) is a schematic cross-sectional view showing the state before current injection, Figure 1 (b) is a schematic cross-sectional view showing the behavior of holes and electrons during current injection.

[0271] Figure 2 This is a schematic cross-sectional view showing a configuration example of a second embodiment of the organic solid-state semiconductor laser of the present invention.

[0272] Figure 3 This is a specific example of a laminate sample used in the first method of the present invention. Figure 3 (a) is a schematic cross-sectional view of a laminate sample. Figure 3(b) is the electric field intensity distribution of the resonance mode of the laminate sample, Figure 3 (c) is an enlarged view of Figure 3 (b) A portion of the diagram.

[0273] Figure 4 It is aimed at Figure 3 (a) shows a graph of the laminate sample showing the dependence of the absorption coefficient α based on the absorption model and the ASE threshold value based on actual measurement on the thickness of the first spacer layer.

[0274] Figure 5 Specific examples of the laminated body sample used in the second method of the present invention are shown. Figure 5 (a) is a schematic cross-sectional view of a laminate sample. Figure 5 (b) is the electric field intensity distribution of the resonance mode of the laminate sample, Figure 5 (c) is an enlarged view of Figure 5 (b) A portion of the diagram.

[0275] Figure 6 It is aimed at Figure 5 (a) shows a graph of the laminate sample showing the dependence of the absorption coefficient α based on the absorption model and the ASE threshold value based on actual measurement on the thickness of the second spacer layer.

[0276] Figure 7 This is an energy level diagram of the organic solid-state semiconductor laser (laser element 1) produced in Example 1.

[0277] Figure 8 Graphs showing calculation results of exciton density distributions of organic solid-state semiconductor lasers (laser elements 2 and 3, comparative laser element 1) fabricated in Examples 2 and 3 and Comparative Example 1.

[0278] Figure 9 1 is a diagram showing the photon band, angular light intensity distribution, and emission spectrum of the organic solid-state semiconductor laser (laser element 1) produced in Example 1. Figure 9 (a) is a graph measured by applying a 5V DC voltage. Figure 9 (b) is a graph obtained by applying a DC voltage of 10 V.

[0279] Figure 10 1 and 2 show the photon band diagram, angular light intensity distribution, and emission spectrum of the organic solid-state semiconductor laser (laser element 2) produced in Example 2.

[0280] Figure 11 1 and 2 show the photon band diagram, angular light intensity distribution, and emission spectrum of the organic solid-state semiconductor laser (laser element 3) produced in Example 3.

[0281] Figure 121 and 2 show the photon band diagram, angular light intensity distribution, and emission spectrum of the organic solid-state semiconductor laser (laser element 4) produced in Example 4.

[0282] Figure 13 1 and 2 show the photon band diagram, angular light intensity distribution, and emission spectrum of the organic solid-state semiconductor laser (comparative laser element 1) produced in Comparative Example 1.

[0283] Figure 14 1 and 2 show the photon band diagram, angular light intensity distribution, and emission spectrum of the organic solid-state semiconductor laser (laser element 5) produced in Example 5.

[0284] Figure 15 1 and 2 show the photon band diagram, angular light intensity distribution, and emission spectrum of the organic solid-state semiconductor laser (laser element 6) produced in Example 6.

[0285] Figure 16 1 and 2 show the photon band diagram, angular light intensity distribution, and emission spectrum of the organic solid-state semiconductor laser (laser element 7) fabricated in Example 7.

[0286] Figure 17 1 and 2 show the photon band diagram, angular light intensity distribution, and emission spectrum of the organic solid-state semiconductor laser (laser element 8) fabricated in Example 8.

[0287] Figure 18 The photon band diagram, angular light intensity distribution, and emission spectrum of the organic solid-state semiconductor laser (laser element 9) produced in Example 9 are shown. Figure 18 (a) is a diagram obtained by measuring from the substrate side. Figure 18 (b) is a diagram obtained by measuring from the cathode side.

[0288] Figure 19 This is a schematic cross-sectional view showing an example of a conventional organic solid-state semiconductor laser.

[0289] Figure 20 FIG. 1 is a diagram showing a comparison between a conventional organic solid-state semiconductor laser and the organic solid-state semiconductor laser according to the first embodiment. Figure 20 (a) is a schematic cross-sectional view showing an example of a conventional organic solid-state semiconductor laser. Figure 20 (b) means Figure 20 (a) is a schematic cross-sectional view showing the behavior of holes and electrons in an organic solid-state semiconductor laser. Figure 20 (c) is a schematic cross-sectional view showing one form of the organic solid-state semiconductor laser according to the first embodiment. Figure 20 (d) means Figure 20 (c) is a schematic cross-sectional view showing the behavior of holes and electrons in an organic solid-state semiconductor laser. DETAILED DESCRIPTION

[0290] Hereinafter, the content of the present invention will be described in detail. The description of the constituent elements recorded below is sometimes completed based on representative embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples. In addition, in this specification, the numerical range represented by "~" refers to a range including the numerical values ​​recorded before and after "~" as the lower limit and upper limit. In addition, the isotope type of the hydrogen atoms present in the molecules of the compound used in the present invention is not particularly limited. For example, the hydrogen atoms in the molecule can be all 1H, or a part or all of them can be 2H (deuterium D). "Transparent" in the present invention means that the visible light transmittance is more than 50%, for example, more than 80%, for example, more than 90%, for example, more than 99%. The visible light transmittance can be measured by an ultraviolet-visible spectrophotometer.

[0291] Organic solid-state semiconductor lasers

[0292] The organic solid-state semiconductor laser of the present invention is characterized by comprising: a hole injection portion for injecting holes; an electron injection portion for injecting electrons; a light-emitting layer for causing holes and electrons to recombine to emit light; and an optical resonator for propagating the emitted light within the light-emitting layer.

[0293] A hole blocking layer is provided on the electron injection portion side of the light-emitting layer so as to be adjacent to the light-emitting layer, or

[0294] An electron blocking layer is provided on the hole injection portion side of the light-emitting layer so as to be adjacent to the light-emitting layer.

[0295] In the following description, in the organic solid semiconductor laser of the present invention, the method of having a hole blocking layer on the electron injection portion side of the light-emitting layer in a manner adjacent to the light-emitting layer is referred to as the "first embodiment", and the method of having an electron blocking layer on the hole injection portion side of the light-emitting layer in a manner adjacent to the light-emitting layer is referred to as the "second embodiment".

[0296] Hereinafter, each configuration of the first embodiment and the second embodiment of the present invention will be described.

[0297] [First embodiment]

[0298] The organic solid semiconductor laser of the first embodiment is at least stacked in sequence with a hole injection portion, a light-emitting layer, a hole blocking layer and an electron injection portion, and has an optical resonator that allows the emitted light to propagate in the light-emitting layer. The organic solid semiconductor laser of the first embodiment may further have a spacer layer between the hole blocking layer and the electron injection portion, and may also have one or more layers between the light-emitting layer and the hole injection portion. Here, the light-emitting layer, the hole blocking layer, the spacer layer and the one or more layers arranged between the light-emitting layer and the hole injection portion can be set as organic layers. In this specification, "organic layer" refers to a layer containing 70% by weight or more of an organic compound, and "organic compound" refers to a compound containing one or more carbon atoms. Among the organic compounds, for example, organic compounds composed only of atoms selected from the group consisting of carbon atoms, hydrogen atoms, oxygen atoms, nitrogen atoms, boron atoms and halogen atoms can be used.

[0299] The specific structure of the first embodiment is shown in FIG. Figure 1 (a). Figure 1 In (a), 11 denotes a hole injection unit, 12 denotes a hole injection layer, 13 denotes a hole transport layer, 14 denotes a light-emitting layer, 15 denotes a hole blocking layer, 16 denotes an electron transport layer, 17 denotes an electron injection unit, and 18 denotes a diffraction grating constituting an optical resonator. Here, electron transport layer 16 constitutes a spacer layer, and hole injection layer 12 and hole transport layer 13 correspond to the aforementioned "one or more layers disposed between the light-emitting layer and the hole injection unit."

[0300] The organic solid semiconductor laser of the first embodiment can achieve high laser efficiency and small peak width of the emission spectrum and the peak width of the angular light intensity distribution by providing the hole blocking layer 15 adjacent to the light emitting layer 14. In addition, by providing a spacer layer 16 between the hole blocking layer 15 and the electron injection part 17 as needed, the laser efficiency can be further improved. Figure 20 , the reason is explained. Figure 20 middle, Figure 20 (a) is a schematic cross-sectional view showing a conventional organic solid semiconductor laser having no hole blocking layer or spacer layer. Figure 20 (b) means Figure 20 (a) is a schematic cross-sectional view of the behavior of carriers in an organic solid-state semiconductor laser. Figure 20 (c) is a schematic cross-sectional view showing one form of the organic solid-state semiconductor laser according to the first embodiment. Figure 20 (d) means Figure 20 (c) is a schematic cross-sectional view showing the behavior of carriers in an organic solid-state semiconductor laser.

[0301] Figure 20The conventional organic solid semiconductor laser shown in (a) has a light emitting layer 202 with a thickness of about 200 nm and a diffraction grating 204 formed of a laser oscillation material between an electron injection portion 201 and a hole injection portion 203, and forms a homogeneous junction structure for injecting carriers from the electron injection portion 201 and the hole injection portion 203 into a single organic semiconductor layer (light emitting layer 202). Figure 20 As shown in (b), in this type of organic solid semiconductor laser with a homojunction structure, when carriers (holes (+) and electrons (-)) are injected from the injection sections 201 and 203 into the light-emitting layer 202, the entire light-emitting layer 202 becomes a carrier recombination region RZ with a low exciton density. L Furthermore, since the light-emitting layer 202 is adjacent to the hole injection portion 203, the light generated in the light-emitting layer 202 is likely to form surface plasmon polaritons on the metal electrode of the hole injection portion 203 or be subjected to light absorption or light scattering by the electrode. The resulting optical loss also becomes a cause of damage to the laser efficiency.

[0302] In this regard, Figure 20 The organic solid semiconductor laser of the first embodiment shown in (c) has a heterojunction structure having at least a light-emitting layer 14 and a hole-blocking layer 15 (two or more organic semiconductor layers) between a hole injection portion 11 and an electron injection portion 17. Figure 20 As shown in (d), when carriers are injected from the respective injection sections 11 and 17, the holes (+) injected into the light-emitting layer 14 are transported toward the hole blocking layer 15 within the light-emitting layer 14. However, the interface 15s between the light-emitting layer 14 and the hole blocking layer 15 acts as a barrier, hindering the migration from the interface 15s to the electron injection section 17. As a result, the holes (+) are retained near the interface 15s, and the retained holes and the electrons (-) that migrate from the hole blocking layer 15 into the light-emitting layer 14 are concentrated to cause carrier recombination, thereby forming a carrier recombination zone RZ with a high exciton density near the interface 15s. H As a result, in the region RZ H The stimulated emission light is generated efficiently, and the peak width of the emission spectrum and the peak width of the angular light intensity distribution are small. Moreover, when the spacer layer 16 is arranged between the hole blocking layer 15 and the electron injection part 17, the carrier recombination region RZ H There is a gap between the electron injection portion 17, so that the carrier recombination region RZ can be suppressed. H The light generated in the process forms surface plasmon polaritons on the electrode surface and is lost, and light loss occurs due to absorption or scattering in the electrode.

[0303] In this way, the organic solid-state semiconductor laser of the present invention concentrates the recombination region, which corresponds to the gain region, in a limited area within the light-emitting layer. Furthermore, by providing a spacer layer or the like as needed to maintain a distance from the electrode that causes loss, the gain is maintained higher than the loss, achieving stable laser oscillation. These features enable further improvements in laser efficiency and monochromaticity, while also contributing to low-voltage operation.

[0304] Hereinafter, each member and each layer of the organic solid-state semiconductor laser according to the first embodiment will be described.

[0305] (Substrate)

[0306] The organic solid-state semiconductor laser of the present invention can be set in a manner such that each component and each layer is supported by a substrate. As a substrate, when the organic solid-state semiconductor laser takes out laser light from the substrate side, a substrate that is translucent to the laser light is used. For example, a transparent substrate composed of glass, transparent plastic, quartz, etc. can be used. On the other hand, when the organic solid-state semiconductor laser is a structure in which the laser light is taken out from the side opposite to the substrate, the substrate is not particularly limited. In addition to the above-mentioned transparent substrate, a substrate composed of silicon, paper, or cloth can also be used. The organic solid-state semiconductor laser of the first embodiment can be formed by sequentially stacking a hole injection portion, a light-emitting layer, a hole blocking layer, and an electron injection portion on a substrate, or can be formed by sequentially stacking an electron injection portion, a hole blocking layer, a light-emitting layer, and a hole injection portion on a substrate.

[0307] (Hole injection section)

[0308] The hole injection unit has the function of injecting holes. For example, when a light-emitting layer is provided adjacent to the hole injection unit, holes are directly injected from the hole injection unit into the light-emitting layer. Furthermore, when there are one or more layers between the light-emitting layer and the hole injection unit, holes are injected from the hole injection unit into the layer adjacent to the one or more layers. Holes transported through the one or more layers are then injected into the light-emitting layer.

[0309] In one embodiment of the present invention, the hole injection portion of the first embodiment is an electrode, for example, a transparent electrode. As for the electrode as the hole injection portion (hereinafter referred to as the "anode"), for example, an electrode having a large work function (above 4 eV), a metal, an alloy, a conductive compound, and a mixture thereof can be used as an electrode material. As specific examples of such electrode materials, conductive transparent materials such as Au, CuI, indium tin oxide (ITO), SnO2, ZnO, and TiN can be cited. In addition, amorphous materials such as IDIXO (In2O3-ZnO) that can be used to make transparent conductive films can also be used. The anode can be formed by forming these electrode materials into films using methods such as evaporation and sputtering. In addition, a pattern of the desired shape can be formed on the formed thin film by photolithography to serve as the anode, or when the pattern accuracy is not much needed (about 100 μm or more), a pattern can be formed through a mask of the desired shape during evaporation or sputtering of the above-mentioned electrode material. Alternatively, when a coatable material such as an organic conductive compound is used, a wet film-forming method such as a printing method or a coating method can be utilized.

[0310] In organic solid-state semiconductor lasers, when the laser light is extracted through the anode, the anode must be transparent. Specifically, to form a transparent anode, for example, the conductive transparent material described above can be used as the anode, or a thin film formed of a metal or alloy with a thickness of 5 to 100 nm can be used as the anode, or an electrode having a DMD structure described later can be used as the anode. The thickness of the metal or alloy thin film is, for example, 40 nm or less, for example, 5 to 30 nm, or even 12 to 25 nm.

[0311] The sheet resistance of the anode is, for example, several hundred Ω / □ or less. The film thickness also depends on the material, but is usually selected from the range of 10 to 1000 nm, for example, 10 to 200 nm.

[0312] (Electron injection unit)

[0313] The electron injection portion has the function of injecting electrons. For example, when a hole-blocking layer is provided adjacent to the electron injection portion, electrons are injected from the electron injection portion into the hole-blocking layer, and the electrons transported through the hole-blocking layer are injected into the light-emitting layer. When a spacer layer is provided between the hole-blocking layer and the electron injection portion, and adjacent to the electron injection portion, electrons are injected from the electron injection portion into the spacer layer, and the electrons transported through the spacer layer and the hole-blocking layer are injected into the light-emitting layer.

[0314] In one embodiment of the present invention, the electron injection portion of the first embodiment is an electrode, for example, a metal electrode. The material of the metal electrode can be any one of a monomer of a metal element, a mixture obtained by mixing monomers of two or more metal elements, an alloy fused with two or more metal elements, a mixture of a monomer of a metal element and an alloy, and a mixture obtained by mixing two or more alloys. As the electrode of the electron injection portion (hereinafter referred to as the "cathode"), a metal (called an electron-injecting metal) or an alloy having a work function smaller than that of the electrode material used in the anode can be used. In addition, as the cathode, a cathode using a conductive compound and a mixture thereof as the electrode material can also be used. Specific examples of such cathode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al2O3) mixture, indium, lithium / aluminum mixture, rare earth metals, etc. Among these, for example, from the perspective of durability against electron injection and oxidation, a mixture of an electron-injecting metal and a metal having a larger work function value than the electron-injecting metal and a stable second metal can be used. For example, a magnesium / silver mixture, a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al2O3) mixture, a lithium / aluminum mixture, aluminum, etc. can be used. In addition, a metal film with a coating such as lithium fluoride provided on the surface of a thin film formed of an electron-injecting metal can also be used as a cathode. The cathode can be formed by forming a film of these electrode materials using a method such as evaporation or sputtering.

[0315] When the laser element is configured to transmit the laser light through the cathode, the cathode needs to be transparent. Specifically, to form a transparent cathode, the electrode material can be formed into a thin film having a thickness of 5 to 100 nm (e.g., less than 40 nm, e.g., 5 to 30 nm, e.g., 12 to 25 nm) and used as the cathode, or a laminated structure (e.g., a laminated structure of ITO / Al / LiF) formed by laminating the above-mentioned coated metal film on a thin film of the conductive transparent material exemplified as the anode material can be used as the cathode, or an electrode having the DMD structure described below can be used as the cathode.

[0316] The sheet resistance of the cathode is, for example, several hundred Ω / □ or less, and the film thickness is usually selected from the range of 10 nm to 5 μm, for example, 50 to 200 nm.

[0317] In one embodiment of the present invention, at least one of the electron injection portion and the hole injection portion is an electrode having a visible light transmittance of 10% or more, for example, 50% or more, 80% or more, or 90% or more.

[0318] (Luminescent layer)

[0319] The light-emitting layer is a layer where holes and electrons injected from the hole injection unit and electron injection unit recombine to generate excitons and form an inversion distribution, thereby causing stimulated emission. The light-emitting layer contains a laser oscillating material (optical gain medium) that can produce such stimulated emission.

[0320] The light-emitting layer may be composed solely of a laser oscillating material, or may be a layer obtained by doping a host material with a laser oscillating material. Furthermore, the light-emitting layer may contain a laser oscillating material and a dopant material. Examples of dopant materials include light-emitting materials and triplet extinction agents. By doping the light-emitting layer with a light-emitting material, the wavelength and color of light emitted by the light-emitting layer can be controlled. Furthermore, by doping the light-emitting layer with a triplet extinction agent, the accumulation of triplet excitons within the light-emitting layer is suppressed, and the generation of high-order excited states caused by collisions between triplet excitons and the degradation of excited molecules caused by these high-order excited states are suppressed. As a result, the luminous efficiency can be improved. In one embodiment of the present invention, the light-emitting layer is a layer composed solely of a laser oscillating material. In one embodiment of the present invention, the light-emitting layer is a layer obtained by doping a host material with a laser oscillating material. In one embodiment of the present invention, the light-emitting layer is a layer obtained by mixing a laser oscillating material and a dopant material. In one embodiment of the present invention, the light-emitting layer is a layer obtained by doping a host material with a laser oscillating material and a dopant material. In one embodiment of the present invention, the dopant material is an organic compound. In one embodiment of the present invention, the dopant material includes a light-emitting material. In one embodiment of the present invention, the dopant material includes a triplet quencher. In one embodiment of the present invention, the dopant material includes a light-emitting material and a triplet quencher.

[0321] The laser oscillating material can be selected from organic compounds having at least one stilbene unit. Here, the stilbene unit has a structure in which at least one hydrogen atom may be substituted by a substituent.

[0322] [Chemical Formula 2]

[0323]

[0324] In one embodiment of the present invention, the laser oscillating material is selected from an organic compound having two or more stilbene units. In the two or more stilbene units, the phenyl groups of adjacent stilbene units may be linked to each other by a single bond at the 4-position and the 4'-position, or may be linked to each other by a single bond at the 4-position and the 3-position and the 3'-position via a methylene group to form a fluorene ring. Here, at least one hydrogen atom of the benzene ring constituting the stilbene unit may be substituted by a substituent (e.g., an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 15 carbon atoms). Furthermore, the hydrogen atom at position 9 (methylene) of the fluorene ring may be substituted by two alkyl groups (e.g., carbon atoms 1 to 10, e.g., carbon atoms 6), and a hydrocarbon ring such as a fluorene ring may be screwed onto the 9-position.

[0325] Specific examples of laser oscillating materials that can be used in the present invention are listed below, but the laser oscillating materials that can be used in the present invention should not be construed as being limited by these specific examples.

[0326] First, as a specific example of a laser oscillating material having a stilbene unit, 4,4'-bis[(N-carbazole)styrene]biphenyl (BSBCz) represented by the following formula can be cited. In one embodiment of the present invention, the light-emitting layer comprises BSBCz. In one embodiment of the present invention, the light-emitting layer is a layer composed solely of BSBCz. In one embodiment of the present invention, the light-emitting layer is a layer obtained by doping a host material with BSBCz. The layer obtained by doping a host material with BSBCz may further contain a dopant material.

[0327] [Chemical Formula 3]

[0328]

[0329] Examples of laser oscillating materials having stilbene units include the following compounds and polymers having the following repeating structures. In the following formula, R1 and R2 represent an alkyl group having 1 to 10 carbon atoms, such as a hexyl group. n and m each independently represent an integer of 2 to 20. n and m may be the same or different.

[0330] [Chemical Formula 4]

[0331]

[0332] Furthermore, the laser oscillation material can also be selected from organic compounds having at least one fluorene ring. As examples of laser oscillation materials having a fluorene ring, the following compounds and polymers having the following repeating structure are listed. In the following formula, R represents an alkyl group having 1 to 10 carbon atoms, for example, a hexyl group. Me represents a methyl group, hexyl represents a hexyl group, and Oct represents an octyl group. n represents an integer from 2 to 30, for example, any number among 2, 3, 4, 5, and 6. In addition, compounds having both a stilbene unit and a fluorene ring are shown above as specific examples of laser oscillation materials having a stilbene unit.

[0333] [Chemical Formula 5]

[0334]

[0335] Furthermore, the laser oscillation material can also be selected from organic compounds having at least one condensed polycyclic structure (julolidine ring) described below.

[0336] [Chemical Formula 6]

[0337]

[0338] Examples of laser oscillation materials having a julolidine ring include the following compounds.

[0339] [Chemical Formula 7]

[0340]

[0341] Among the above laser oscillating materials, for example, by using a material other than a polymer (monomer-polymer), a light-emitting layer can be easily produced by a vapor deposition method.

[0342] The luminescent material used as a dopant material can be, for example, a luminescent organic compound, which can be any one of a fluorescent material, a delayed fluorescent material, and a phosphorescent material. In this specification, a "fluorescent material" refers to a luminescent material whose fluorescence intensity is higher than the luminescence intensity of phosphorescence when the luminescence is observed at 20°C, and a "phosphorescent material" refers to a luminescent material whose phosphorescence intensity is higher than the luminescence intensity of fluorescence when the luminescence is observed at 20°C. Furthermore, a "delayed fluorescent material" refers to a material in which both fluorescence with a short luminescence lifetime and fluorescence with a long luminescence lifetime (delayed fluorescence) are observed at 20°C. The luminescence lifetime of ordinary fluorescence (fluorescence that is not delayed fluorescence) is on the order of ns, and the luminescence lifetime of phosphorescence is generally on the order of ms, so fluorescence and phosphorescence can be distinguished by the luminescence lifetime. Furthermore, luminescent organic compounds other than organometallic complexes are generally fluorescent materials or delayed fluorescent materials.

[0343] Furthermore, the luminescent material used as a dopant material may be an organic compound known as an optical gain medium. The compound used as the luminescent material is different from the compound used as the laser oscillation material in the organic solid-state semiconductor laser. The structure and driving conditions of the optical resonator of the organic solid-state semiconductor laser used in the present invention are designed based on the conditions (e.g., emission wavelength, oscillation threshold) of the organic compound selected as the laser oscillation material so that the organic compound can oscillate.

[0344] The emission wavelength and color of the luminescent material are appropriately selected according to the oscillation wavelength of the laser oscillator material and the target emission wavelength and color. For example, the emission wavelength of the luminescent material can be selected from the visible region, the infrared region, or the ultraviolet region.

[0345] For specific examples of luminescent materials, reference can be made to the examples of compounds exemplified by fluorene-based molecules, styrene-based molecules, carbazole-styrene biphenyl compounds, TADF materials (thermally activated delayed fluorescence materials), star-shaped polymers, polyfluorenes, phenylene vinylene polymers, and ladder-shaped polymers described in Adv.Photonics Res.2021, 2, 2000155, and CCS Chem.2020, 2, 1203-1216. Here, a "star-shaped polymer" refers to a polymer having three or more branched chains extending radially from a common center (e.g., a benzene nucleus, a pyrene nucleus, or a phenylene indenyl acene nucleus), and a "ladder-shaped polymer" refers to a polymer in which monomer units are connected by two or more bonds. Representative examples of these compounds are listed below. Unless otherwise specified, n represents an integer of 2 to 20.

[0346] [Chemical Formula 8-1]

[0347]

[0348] [Chemical Formula 8-2]

[0349]

[0350] [Chemical Formula 8-3]

[0351]

[0352] These light-emitting materials may be used alone or in combination of two or more.

[0353] The triplet extinction agent can be a compound having a lower lowest excited triplet energy than the laser oscillating material. For example, a compound having a lower lowest excited triplet energy than the laser oscillating material and a higher lowest excited singlet energy can be used. The triplet extinction agent can be selected, for example, from organic compounds containing an anthracene ring. Specific examples of triplet extinction agents containing an anthracene ring are shown below.

[0354] [Chemical Formula 9]

[0355]

[0356] As the host material, an organic compound can be used in which at least one of the excited singlet energy and the excited triplet energy has a value higher than that of the laser oscillation material. Thus, the singlet excitons and triplet excitons generated in the laser oscillation material can be confined to the molecules of the laser oscillation material, and the threshold current density for generating laser oscillation can be reduced. Of course, sometimes even if the singlet excitons and triplet excitons cannot be fully restricted, it can also help to lower the threshold and improve the laser characteristics. Therefore, as long as it is a host material that can achieve the reduction of the threshold and the improvement of the laser characteristics, it can be used in the present invention without particular restrictions. In the organic solid semiconductor laser of the present invention, the light emitted by the laser oscillation material under stimulation is propagated in the light-emitting layer through the action of an optical resonator, etc., becomes laser light and is emitted to the outside. The light emitted by the laser element can include natural emission light and naturally emitted amplified light from the laser oscillation material, and can also include light emitted from the host material, but for example, laser light is the main component.

[0357] When a host material is used, the content of the laser oscillation material in the light-emitting layer is, for example, greater than 0.1 weight %, for example, greater than 0.5 weight %, for example, greater than 1 weight %, and, for example, less than 99 weight %, for example, less than 90 weight %, for example, less than 70 weight %, and, for example, less than 50 weight % or less than 30 weight %, for example, less than 15 weight %.

[0358] As the host material in the light-emitting layer, for example, an organic compound having hole transport capability, electron transport capability, and preventing the emission of light at a long wavelength and having a high glass transition temperature can be used. As the host material, it is possible to appropriately select and use from known host materials taking into account the energy conditions and physical properties as described above.

[0359] Furthermore, materials constituting the light-emitting layer (laser oscillator material, host material) can be materials with hole mobility equal to or greater than that of BSBCz. This allows holes to be efficiently retained near the interface between the light-emitting layer and the hole-blocking layer, leading to more concentrated carrier recombination in this region. The hole mobility of the light-emitting layer can be greater than the electron mobility, for example, at least 10 times greater. The thickness of the light-emitting layer can be, for example, at least 10 nm, for example, at least 30 nm, at least 50 nm, or at least 70 nm, and can be, for example, less than 200 nm, for example, less than 150 nm or less than 100 nm.

[0360] The thickness of the light-emitting layer can be selected from the range of, for example, 10 nm to less than 200 nm.

[0361] (Hole Blocking Layer)

[0362] The hole blocking layer can be provided adjacent to the light emitting layer, for example, in contact with the light emitting layer. In a preferred embodiment of the present invention, the hole blocking layer is formed along a flat interface of the light emitting layer.

[0363] like Figure 1 As shown in (b), the hole blocking layer 15 has the function of preventing the holes (+) transported toward the hole blocking layer 15 side in the light-emitting layer 14 from migrating from the interface between the light-emitting layer 14 and the hole blocking layer 15 to the electron injection portion 17 side. As a result, the holes are retained near the interface between the light-emitting layer 14 and the hole blocking layer 15, and are recombined with the electrons (-) migrating from the hole blocking layer 15 into the light-emitting layer 14. As a result, carrier recombination occurs intensively near the interface, and stimulated emission light is efficiently generated, which can achieve laser radiation with a small peak width of the emission spectrum and a small peak width of the angular light intensity distribution. In addition, here, Figure 1 The effects of the present invention will be described using the laser element as an example. However, the structure of the organic solid-state semiconductor laser of the present invention should not be interpreted as being limitative of this specific example.

[0364] To demonstrate this hole-blocking function, the hole-blocking layer is selected to have a material such that the absolute value of the HOMO (Highest Occupied Molecular Orbital) energy of the hole-blocking layer is greater than the absolute value of the HOMO energy of the light-emitting layer. For example, the absolute value of the HOMO energy of the hole-blocking layer may be greater than the absolute value of the HOMO energy of the light-emitting layer by 0.1 eV, 0.2 eV, or 0.4 eV.

[0365] Furthermore, the hole blocking layer can be made of a material with low hole mobility, for example. Specific examples of the material for the hole blocking layer include TPBi ([1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene]) or T2T (2,4,6-tris([1,1'-biphenyl]-3-yl))-1,3,5-triazine. Furthermore, the material for the hole blocking layer can be selected from the group consisting of a material having a hole mobility equal to or lower than TPBi and a material having a hole mobility equal to or lower than T2T.

[0366] Furthermore, the material of the hole blocking layer can be selected from the group of compounds having a nitrogen-containing aromatic heterocycle, for example, it can also be selected from the group of compounds having a structure in which a nitrogen-containing aromatic heterocycle is bonded to an aromatic hydrocarbon ring. Examples of nitrogen-containing aromatic heterocycles include nitrogen-containing aromatic 6-membered rings such as pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, and triazine ring, azole rings such as imidazole ring, thiazole ring, and oxazole ring, and condensed rings formed by condensation of these nitrogen-containing aromatic 6-membered rings or azole rings with aromatic hydrocarbon rings. The aromatic hydrocarbon ring may be a single ring or a condensed ring formed by condensation of two or more rings. In the case of a condensed ring, the number of condensed rings can be selected from the range of 2 to 6, for example. Specific examples of rings include benzene rings and naphthalene rings.

[0367] The thickness of the hole blocking layer is, for example, 1 nm or more, for example, 3 nm or more, for example, 5 nm or more, or 8 nm or more, and is, for example, 80 nm or less, for example, 30 nm or less, or 15 nm or less.

[0368] (Spacer layer)

[0369] The spacer layer used in the first embodiment is a layer provided between the hole-blocking layer and the electron-injecting portion as needed. By placing the spacer layer between the hole-blocking layer and the electron-injecting portion, a gap is created between the carrier recombination region (near the interface between the light-emitting layer and the hole-blocking layer) and the electron-injecting portion. This prevents light generated in the carrier recombination region from being lost as surface plasmon polaritons on the electrode surface, or from being lost due to absorption or scattering in the electrode.

[0370] The spacer layer can be a single-layer structure or a multi-layer structure. Furthermore, when one or more layers are provided between the light-emitting layer and the hole injection portion, the total thickness of the spacer layer can be set to more than twice the total thickness of the layers between the light-emitting layer and the hole injection portion, for example, it can be set to more than 2.5 times or more than 3 times. For the description of the one or more layers provided between the light-emitting layer and the hole injection portion, reference can be made to the description of the "other layers" column below. By making the spacer layer thicker than the layer between the light-emitting layer and the hole injection portion, the migration distance of electrons becomes longer than the migration distance of holes, thereby suppressing excessive entry of electrons into the light-emitting layer. As a result, carrier recombination can be concentrated in a narrower area. Furthermore, the spacer layer can be composed of a material having a lower refractive index than the light-emitting layer, for example. Thus, light from the light-emitting layer is efficiently reflected at the interface of the light-emitting layer side of the spacer layer, thereby further reliably suppressing light loss in the electrode as described above.

[0371] The spacer layer used in the first embodiment may be, for example, a layer (electron transport layer) that can transport electrons injected from the electron injection portion toward the hole blocking layer and has electron transport properties.

[0372] (Electron Transport Layer)

[0373] TPBi is a specific example of a material for the electron transport layer. Alternatively, the material for the electron transport layer can be selected from the group of electron transport compounds having an electron mobility equal to or lower than that of TPBi. The low electron mobility of the electron transport layer can suppress excessive electron ingress into the light-emitting layer, allowing carrier recombination to occur in a more confined area.

[0374] Furthermore, the material for the electron transport layer can be selected from the group of compounds having nitrogen-containing aromatic heterocycles, for example, or the group of compounds having a structure in which a nitrogen-containing aromatic heterocycle is bonded to an aromatic hydrocarbon ring. For descriptions and specific examples of nitrogen-containing aromatic heterocycles and aromatic hydrocarbon rings, reference can be made to the description of nitrogen-containing aromatic heterocycles and aromatic hydrocarbon rings described in the hole-blocking layer section. The material for the electron transport layer can be different from that for the hole-blocking layer.

[0375] In one embodiment of the present invention, the electron transport layer has a HOMO energy greater than that of the light emitting layer. Specifically, the HOMO energy of the electron transport layer may be greater than that of the light emitting layer by 0.1 eV or more, for example, by 0.2 eV or more.

[0376] The thickness of the electron transport layer is, for example, 10 nm or more, for example, 20 nm or more, for example, 40 nm or more, or 60 nm or more, and is, for example, 100 nm or less, for example, 80 nm or less.

[0377] (Other layers)

[0378] The organic solid-state semiconductor laser of the first embodiment may have one or more layers between the light-emitting layer and the hole injection unit as needed. Examples of layers provided between the light-emitting layer and the hole injection unit include a hole injection layer and a hole transport layer. The hole injection layer is a layer having the function of reducing the hole injection barrier in the hole injection unit, and the hole transport layer is a layer having the function of transporting holes injected from the hole injection unit to the light-emitting layer side. The hole transport layer may be a hole injection transport layer having a hole injection function.

[0379] Examples of materials for the hole transport layer include triazole derivatives, oxadiazole derivatives, imidazole derivatives, carbazole derivatives, indolecarbazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, aromatic amine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, especially thiophene oligomers, and the like. For example, the material can be selected from the group of compounds including porphyrin compounds, aromatic tertiary amine compounds and styrylamine compounds, or from the group of compounds including aromatic tertiary amine compounds.

[0380] As a specific example of the material of the hole transport layer, NPD can be cited. In addition, the material of the hole transport layer can also be selected from the group of compounds having a hole mobility equivalent to or higher than that of NPD. As a specific example of the material of the hole injection layer, HATCN ([dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile]) can be cited. In addition, the material of the hole injection layer can also be selected from the group of compounds having a LUMO energy level or a HOMO energy level between the Fermi level of the hole injection part and the HOMO energy level of the light-emitting layer. Furthermore, between the light-emitting layer and the hole injection part, for example, there can be a layer composed of a material having a hole mobility equivalent to or higher than that of HATCN.

[0381] (Optical Resonator)

[0382] The optical resonator propagates the emitted light within the light-emitting layer. It can be a distributed feedback (DFB) or distributed reflectance (DBR) optical resonator, where light is reflected by a diffraction grating. It can also be a Fabry-Perot optical resonator, which consists of a reflector and a partial reflector positioned opposite each other.

[0383] The diffraction grating constituting the optical resonator is designed to satisfy the following Bragg equation. The diffraction grating used in the optical resonator can be any of the following: a first-order diffraction grating with m = 1, a second-order diffraction grating with m = 2, or a third-order diffraction grating with m = 3. Higher-order diffraction gratings are also possible. Furthermore, a mixed-order diffraction grating combining diffraction gratings of different orders is also possible.

[0384] Bragg equation: mλ Bragg =2 neff Λ m

[0385] Here, m is the diffraction order, λ Bragg is the Bragg wavelength, and Λ is the period of the diffraction grating.

[0386] In one embodiment of the present invention, the diffraction grating constituting the optical resonator is a diffraction grating having a periodic concave-convex structure in which grating convex portions and concave portions (grating concave portions) separated by the grating convex portions are periodically arranged. This type of diffraction grating can be a one-dimensional diffraction grating in which grating convex portions are arranged horizontally in a line, a two-dimensional diffraction grating in which grating convex portions are arranged vertically and horizontally in a line, a two-dimensional diffraction grating in which rectangular grating convex portions are arranged in a matrix, or a three-dimensional diffraction grating in which two-dimensional diffraction gratings are stacked in the height direction. Here, the diffraction grating can be configured, for example, so that at least a portion of the grating convex portion intrudes into the interior of the light-emitting layer from the hole injection portion side of the light-emitting layer. In the following description, the portion of the grating convex portion that intrudes into the interior of the light-emitting layer is referred to as the "intrusion portion." The length of the intrusion portion of the grating convex portion can be selected from a range in which the length of the intrusion portion is shorter than the thickness of the light-emitting layer, for example, the length of the intrusion portion can be selected from a range in which the length of the intrusion portion is shorter than the thickness of the light-emitting layer by at least 15 nm. This ensures carrier recombination zones in areas not intruded by the grating protrusions, enabling efficient carrier recombination and stimulated emission. This type of diffraction grating can be formed, for example, on the surface of the electrode that forms the hole injection unit, on the light-emitting layer side. In this case, the grating protrusions are formed on the surface of the electrode on the light-emitting layer side, allowing the electrode surface to be exposed from the bottom of the grating concave sections.

[0387] Furthermore, the diffraction grating can be arranged between the region that becomes the carrier recombination region of the light-emitting layer and the hole injection portion, and the base end portion of the grating protrusion of the diffraction grating can be arranged at the interface on the hole injection portion side of the light-emitting layer or at a position closer to the hole injection portion side than the interface, and the hole blocking layer can be arranged between the light-emitting layer and the electron injection portion and at a position adjacent to the light-emitting layer.

[0388] The grating protrusions can be made of, for example, an insulating material. The insulating material can be an inorganic insulating material or an organic insulating material. Specific examples of insulating materials include glass, silicon dioxide, and plastic.

[0389] [Second embodiment]

[0390] Next, a second embodiment of the organic solid-state semiconductor laser will be described.

[0391] The organic solid semiconductor laser of the second embodiment is composed of at least a hole injection portion, an electron blocking layer, a light emitting layer and an electron injection portion stacked in sequence, and has an optical resonator that allows the emitted light to propagate in the light emitting layer. The organic solid semiconductor laser of the second embodiment may further have a spacer layer between the electron blocking layer and the hole injection portion, and may also have one or more layers between the light emitting layer and the electron injection portion. Here, the electron blocking layer, the light emitting layer, the spacer layer and the one or more layers arranged between the light emitting layer and the electron injection portion can be set as organic layers. The specific structure of the second embodiment is shown in FIG. Figure 2 .exist Figure 2 In the figure, 21 denotes a hole injection unit, 22 denotes a hole transport layer, 23 denotes an electron blocking layer, 24 denotes a light-emitting layer, 25 denotes an electron transport layer, 26 denotes an electron injection layer, 27 denotes an electron injection unit, and 28 denotes a diffraction grating constituting an optical resonator. Here, hole transport layer 22 constitutes a spacer layer, while electron transport layer 25 and hole injection layer 26 correspond to the aforementioned "one or more layers disposed between the light-emitting layer and the electron injection unit."

[0392] The following describes the various layers and components that make up the organic solid-state semiconductor laser of the second embodiment. For descriptions of the substrate and the light-emitting layer, reference can be made to the descriptions of the "substrate" and "light-emitting layer" sections in the first embodiment. The organic solid-state semiconductor laser of the second embodiment may be formed by sequentially stacking a hole injection portion, an electron blocking layer, a light-emitting layer, and an electron injection portion on a substrate, or may be formed by sequentially stacking an electron injection portion, a light-emitting layer, an electron blocking layer, and a hole injection portion on a substrate.

[0393] (Hole injection section)

[0394] The hole injection portion has the function of injecting holes. For example, when an electron blocking layer is provided adjacent to the hole injection portion, holes are injected from the hole injection portion into the electron blocking layer, and holes transported through the electron blocking layer are injected into the light-emitting layer. Furthermore, when a spacer layer is provided between the electron blocking layer and the hole injection portion, and adjacent to the hole injection portion, holes are injected from the hole injection portion into the spacer layer, and holes transported through the spacer layer and the electron blocking layer are injected into the light-emitting layer.

[0395] In one aspect of the present invention, the hole injection unit of the second embodiment is an electrode, for example, a transparent electrode. For description and specific examples of the electrode (anode) serving as the hole injection unit, refer to the description of the "hole injection unit" section in the first embodiment.

[0396] (Electron injection unit)

[0397] The electron injection section has the function of injecting electrons into the laser element. For example, when a light-emitting layer is provided adjacent to the electron injection section, electrons are directly injected from the electron injection section into the light-emitting layer. Furthermore, when there is one or more layers between the light-emitting layer and the electron injection section, electrons are injected from the electron injection section into the layer adjacent to the one or more layers. Electrons transferred through the one or more layers are then injected into the light-emitting layer.

[0398] In one aspect of the present invention, the electron injection portion of the second embodiment is an electrode, for example, a metal electrode. For a description and specific examples of the electrode (cathode) serving as the electron injection portion, refer to the description of the "electron injection portion" in the first embodiment.

[0399] (Electron blocking layer)

[0400] The electron blocking layer can be provided adjacent to the light-emitting layer, for example, in contact with the light-emitting layer. In a preferred embodiment of the present invention, the electron blocking layer is formed along a flat interface of the light-emitting layer.

[0401] The electron blocking layer has the function of preventing electrons that are transported toward the electron blocking layer in the light-emitting layer from migrating from the interface between the light-emitting layer and the electron blocking layer to the hole injection portion. Figure 2 As shown in FIG, electrons (e-) are retained near the interface between the light-emitting layer and the electron blocking layer, and recombine with holes that migrate from the electron blocking layer into the light-emitting layer. As a result, carrier recombination occurs intensively near the interface, and stimulated emission light is efficiently generated, enabling laser emission with a small peak width of the emission spectrum and a small peak width of the angular light intensity distribution. Figure 2 The effects of the present invention will be described using the laser element as an example. However, the structure of the organic solid-state semiconductor laser of the present invention should not be interpreted as being limitative of this specific example.

[0402] To achieve this electron-blocking function, the electron-blocking layer is selected to have a material such that the absolute value of the LUMO (Lowest Unoccupied Molecular Orbital) energy of the electron-blocking layer is smaller than the absolute value of the LUMO energy of the light-emitting layer. For example, the absolute value of the LUMO energy of the electron-blocking layer may be smaller than the absolute value of the LUMO energy of the light-emitting layer by at least 0.1 eV, at least 0.2 eV, or at least 0.4 eV.

[0403] Furthermore, the electron blocking layer can be made of, for example, a material with low electron mobility. A specific example of a material for the electron blocking layer is NPD (N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine). Alternatively, the material for the electron blocking layer can be selected from a group of materials having an electron mobility equal to or lower than that of NPD.

[0404] The thickness of the electron blocking layer is, for example, 1 nm or more, for example, 3 nm or more, for example, 5 nm or more, or 8 nm or more, and is, for example, 80 nm or less, for example, 30 nm or less, or 15 nm or less.

[0405] (Spacer layer)

[0406] The spacer layer used in the second embodiment is a layer provided between the electron blocking layer and the hole injection portion as needed. By disposing the spacer layer between the electron blocking layer and the hole injection portion, a gap is created between the carrier recombination region (near the interface between the light-emitting layer and the electron blocking layer) and the hole injection portion. This can suppress light generated in the carrier recombination region from being lost as surface plasmon polaritons on the electrode surface, or from light loss due to absorption or scattering in the electrode.

[0407] The spacer layer can be a single-layer structure or a multi-layer structure. Furthermore, when one or more layers are provided between the light-emitting layer and the electron injection portion, the total thickness of the spacer layer can be set to more than twice the total thickness of the layers between the light-emitting layer and the electron injection portion, for example, it can be set to more than 2.5 times or more than 3 times. For the description of the one or more layers provided between the light-emitting layer and the electron injection portion, reference can be made to the description of the "other layers" column below. By making the spacer layer thicker than the layer between the light-emitting layer and the electron injection portion, the migration distance of the holes becomes longer than the migration distance of the electrons, thereby suppressing excessive entry of holes into the light-emitting layer. As a result, carrier recombination can be concentrated in a narrower area. Furthermore, the spacer layer can be composed of a material having a lower refractive index than the light-emitting layer, for example. Thus, the light from the light-emitting layer is efficiently reflected at the interface of the light-emitting layer side of the spacer layer, thereby further reliably suppressing the light loss in the electrode as described above.

[0408] The spacer layer used in the second embodiment may be, for example, a layer (hole transport layer) that can transport holes injected from the hole injection portion toward the electron blocking layer and has hole transport properties.

[0409] (Hole Transport Layer)

[0410] The hole transport layer can be made of a hole-transporting compound with a hole mobility equal to or lower than that of HATCN. The low hole mobility of the hole transport layer prevents excessive hole intrusion into the light-emitting layer, allowing carrier recombination to occur in a more confined area. Furthermore, the hole transport layer can be made of a material different from that of the electron blocking layer.

[0411] In one embodiment of the present invention, the hole transport layer has a LUMO energy having an absolute value smaller than that of the light emitting layer. Specifically, the LUMO energy of the hole transport layer may be smaller by at least 0.1 eV, for example, at least 0.2 eV.

[0412] The thickness of the hole transport layer is, for example, 10 nm or more, for example, 20 nm or more, for example, 40 nm or more, or 60 nm or more, and is, for example, 100 nm or less, for example, 80 nm or less.

[0413] (Other layers)

[0414] The organic solid semiconductor laser of the second embodiment may have one or more layers between the light-emitting layer and the electron injection portion as needed. Examples of layers provided between the light-emitting layer and the electron injection portion include an electron injection layer and an electron transport layer. The electron injection layer is a layer having a function of reducing the electron injection barrier in the electron injection portion, and the electron transport layer is a layer having a function of transporting electrons injected from the electron injection portion to the light-emitting layer side. The electron transport layer may be an electron injection transport layer having an electron injection function.

[0415] As materials for the electron transport layer, for example, nitro-substituted fluorene derivatives, dibenzoquinone derivatives, thiopyran dioxide derivatives, carbodiimides, fluorenylmethane derivatives, anthraquinone dimethane and anthrone derivatives, oxadiazole derivatives, etc. can also be mentioned. Moreover, among the above-mentioned oxadiazole derivatives, thiadiazole derivatives in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and quinoxaline derivatives having a quinoxaline ring known as an electron-withdrawing group can also be used as electron transport materials. In addition, polymer materials in which these materials are introduced into the polymer chain or polymer materials in which these materials are used as the main chain of the polymer can also be used.

[0416] TPBi is a specific example of a material for the electron transport layer. Alternatively, the material for the electron transport layer can be selected from a group of compounds having an electron mobility equivalent to or greater than that of TPBi.

[0417] (Optical Resonator)

[0418] Regarding the description of the optical resonator, reference can be made to the description of the “optical resonator” in the first embodiment, except for the description of the arrangement of the diffraction grating and the intrusion portion of the grating protrusion.

[0419] In the diffraction grating used in the second embodiment, for example, it is possible to configure such that at least a portion of the grating protrusions penetrates into the interior of the light-emitting layer from the electron injection portion side of the light-emitting layer. In the grating protrusions, the length of the intrusion portion that penetrates into the light-emitting layer can be selected from a range where the length of the intrusion portion is shorter than the thickness of the light-emitting layer, for example, it can be selected from a range that is at least 15 nm shorter than the thickness of the light-emitting layer. As a result, a carrier recombination region is ensured in the area where the grating protrusions do not penetrate, and carrier recombination and stimulated emission can be efficiently generated there. This type of diffraction grating can be formed, for example, on the surface of the light-emitting layer side of the electrode that constitutes the electron injection portion. In this case, the grating protrusions are formed on the surface of the electrode on the light-emitting layer side, and the electrode surface can be exposed from the bottom of the grating recesses.

[0420] Furthermore, the diffraction grating can be arranged between the region that becomes the carrier recombination region of the light-emitting layer and the electron injection portion, and the base end portion of the grating protrusion of the diffraction grating can be arranged at the interface on the electron injection portion side of the light-emitting layer or at a position closer to the electron injection portion side than the interface, and the electron blocking layer can be arranged between the light-emitting layer and the hole injection portion and at a position adjacent to the light-emitting layer.

[0421] The organic solid-state semiconductor lasers of the first and second embodiments may be surface-emitting laser elements that emit laser light from the surface, or may be end-emitting laser elements that emit laser light from the end face. Furthermore, in the case of a surface-emitting laser element, it may be a bottom-emitting type that emits laser light from the substrate side, or a top-emitting type that emits laser light from the side opposite to the substrate. Furthermore, the organic solid-state semiconductor lasers of the first and second embodiments may be dual-emitting laser elements in which the back side is visible from the front side. In addition, each type of laser element may leak laser light from a surface other than the surface set as the laser light emission surface, for example, from a laser light emission surface set as the majority (more than 50%) of the laser light.

[0422] In an organic solid semiconductor laser in which the electron injection portion is located on the side opposite to the substrate across the light-emitting layer, a top-emitting organic solid semiconductor laser can be provided by forming the electron injection portion from a material with high transmittance. In one embodiment of the present invention, the electron injection portion is set to a DMD structure with high transmittance, a thin Ag layer (for example, a thickness of 40 nm or less, for example, 5 to 30 nm, for example, 12 to 25 nm). Furthermore, a bottom-emitting organic solid semiconductor laser can be provided by forming the hole injection portion from a material with high transmittance. In one embodiment of the present invention, the hole injection portion is set to an ITO layer. Furthermore, a dual-emission organic solid semiconductor laser can also be provided by forming both the electron injection portion and the hole injection portion from a material with high transmittance.

[0423] On the other hand, in an organic solid semiconductor laser in which a hole injection portion is located on the side opposite to the substrate across a light-emitting layer, a top-emitting organic solid semiconductor laser can be provided by forming the hole injection portion from a material with high transmittance. In one embodiment of the present invention, the hole injection portion is set to a DMD structure or an ITO layer with high transmittance. Furthermore, a bottom-emitting organic solid semiconductor laser can be provided by forming the electron injection portion from a material with high transmittance. In one embodiment of the present invention, the electron injection portion is set to a stacked structure of ITO / Al / LiF. Here, the thickness of Al and LiF is selected from the range of 0.5 to 10 nm. Furthermore, a dual-emission organic solid semiconductor laser can also be provided by forming both the hole injection portion and the electron injection portion from a material with high transmittance.

[0424] Here, "DMD structure" is an abbreviation of dielectric-metal-dielectric structure, which refers to a laminated structure of dielectric / metal / dielectric. In the present invention, the DMD structure can be adopted as an electrode that utilizes the interference of the laminated structure. As the metal constituting the DMD structure, Ag, etc. can be used. In addition, as the dielectric constituting the DMD structure, MoO3, ITO, ZnS, InZnSnO, and WO3 can be used. The materials of the two dielectric layers arranged on both sides of the metal layer can be the same or different. In one embodiment of the present invention, the materials of the two dielectric layers of the DMD structure are the same. As the DMD structure, in addition to MoO3 / Ag / MoO3 used in the embodiment, ITO / Ag / ITO, ZnS / Ag / ZnS, ZnO / Ag / ZnO, InZnSnO / Ag / InZnSnO, ITO / Ag / WO3, ZnO / Ag / WO3, WO3 / Ag / WO3, etc. can also be used.

[0425] The thicknesses of the two dielectric layers disposed on both sides of the metal layer may be the same as or different from each other.

[0426] Furthermore, by controlling the refractive index of each layer that constitutes an organic solid-state semiconductor laser, light generated in the laser oscillating material is confined within the optical resonator. This suppresses light loss in the electrodes and lowers the laser oscillation threshold. Specifically, the refractive index of each layer can be controlled as follows.

[0427] In one embodiment of the present invention, the organic solid semiconductor laser is configured as the first embodiment, and the refractive index of the layer (hole blocking layer or hole blocking layer and spacer layer) disposed between the light-emitting layer and the electron injection portion is less than the refractive index of the light-emitting layer. In one embodiment of the present invention, the organic solid semiconductor laser is configured as the second embodiment, and the refractive index of the layer (e.g., electron injection layer, electron transport layer) disposed between the light-emitting layer and the electron injection portion is less than the refractive index of the light-emitting layer. In organic solid semiconductor lasers of this type, the light generated by the laser oscillation material is efficiently reflected at the interface of the light-emitting layer and the layer adjacent to the electron injection portion of the light-emitting layer and is confined in the optical resonator (refractive index waveguide) or forms a gain waveguide, which can efficiently induce laser oscillation. Moreover, the laser light generated here can be taken out by, for example, transmitting the layer between the light-emitting layer and the hole injection portion or the hole injection portion, the substrate, so that the organic solid semiconductor lasers of these types can be used as bottom-emitting laser elements, for example.

[0428] In one embodiment of the present invention, the organic solid semiconductor laser is configured as a first embodiment, and the refractive index of the layer (for example, hole injection layer, hole transport layer) disposed between the light-emitting layer and the hole injection portion is less than the refractive index of the light-emitting layer. In one embodiment of the present invention, the organic solid semiconductor laser is configured as a second embodiment, and the refractive index of the layer (electron blocking layer or electron blocking layer and spacer layer) disposed between the light-emitting layer and the hole injection portion is less than the refractive index of the light-emitting layer. In organic solid semiconductor lasers of this type, the light generated by the laser oscillation material is efficiently reflected at the interface between the light-emitting layer and the layer adjacent to the hole injection portion of the light-emitting layer and is confined within the optical resonator (refractive index waveguide) or forms a gain waveguide, thereby efficiently inducing laser oscillation. Furthermore, the laser light generated here can be taken out by, for example, transmitting the layer or electron injection portion between the light-emitting layer and the electron injection portion, so that the organic solid semiconductor lasers of these types can be used as top-emitting laser elements, for example.

[0429] In one embodiment of the present invention, an organic solid-state semiconductor laser is configured as the first embodiment, wherein the refractive index of the layer disposed between the light-emitting layer and the electron injection portion, and the refractive index of the layer disposed between the light-emitting layer and the hole injection portion, are each smaller than the refractive index of the light-emitting layer. In one embodiment of the present invention, an organic solid-state semiconductor laser is configured as the second embodiment, wherein the refractive index of the layer disposed between the light-emitting layer and the electron injection portion, and the refractive index of the layer disposed between the light-emitting layer and the hole injection portion, are each smaller than the refractive index of the light-emitting layer. In an organic solid-state semiconductor laser of this embodiment, light generated by the laser oscillating material is efficiently reflected at interfaces between the light-emitting layer and adjacent layers on both sides, confining it within the optical resonator. Therefore, the light can propagate laterally within the light-emitting layer and efficiently induce laser oscillation. Furthermore, in one embodiment of the present invention, the organic solid-state semiconductor laser is configured as the first embodiment or the second embodiment, wherein the gain is high in the central portion of the lateral optical path of the light-emitting layer. In an organic solid-state semiconductor laser of this embodiment, since light passing through the central portion of the lateral optical path is greatly amplified, the light naturally propagates along this lateral optical path (high-gain region). Furthermore, in organic solid-state semiconductor lasers of these types, light only needs to propagate in the transverse direction in the light-emitting layer, and the final light extraction direction can also be set to the longitudinal direction.

[0430] The organic solid semiconductor lasers of these modes are characterized in that, in the case of the first embodiment, the migration of holes advancing in the longitudinal direction is hindered (blocked) by the hole blocking layer relative to the lateral propagation of light, and in the case of the second embodiment, the migration of electrons advancing in the longitudinal direction is hindered (blocked) by the electron blocking layer relative to the lateral propagation of light.

[0431] As described above, the organic solid semiconductor laser of the present invention has a hole blocking layer or an electron blocking layer, and carrier recombination occurs near the interface of the light-emitting layer and the hole blocking layer or near the interface of the light-emitting layer and the electron blocking layer, and the peak width of the luminescence spectrum and the peak width of the angular light intensity distribution become smaller. As a result, an organic solid semiconductor laser with excellent laser characteristics such as laser efficiency and monochromaticity is achieved. Here, the "peak width of the luminescence spectrum" in this specification refers to the half width (FWHM) of the luminescence peak with the largest intensity among the luminescence peaks appearing in the light intensity distribution (luminescence spectrum) relative to the wavelength, and the "peak width of the angular light intensity distribution" refers to the half width (FWHM) of the luminescence peak with the largest intensity among the luminescence peaks appearing in the light intensity distribution measured by changing the angle of the light-receiving element. The peak width of the luminescence spectrum observed in the organic solid semiconductor laser of the present invention is, for example, less than 10nm, for example, less than 7nm, for example, less than 5nm, for example, less than 4nm, for example, less than 3nm, for example, less than 2nm, for example, less than 1nm. The peak width of the angular light intensity distribution observed in the organic solid semiconductor laser of the present invention is, for example, 10° or less, 7° or less, 5° or less, 4° or less, 3° or less, 2° or less, or 1° or less.

[0432] <Method for reducing the half-width of the emission wavelength peak in the emission spectrum>

[0433] Next, a method for reducing the half width of the emission wavelength peak (peak width of the emission spectrum) of the emission spectrum of the present invention will be described.

[0434] The method of the present invention is a method for reducing the full width at half maximum (FWHM) of the emission wavelength peak of the emission spectrum of an organic electroluminescent element, wherein:

[0435] The organic electroluminescent element comprises:

[0436] a hole injection portion for injecting holes;

[0437] an electron injection unit for injecting electrons; and

[0438] The light-emitting layer is arranged between the hole injection part and the electron injection part, and the holes and electrons are recombined to emit light.

[0439] The light generated in the light-emitting layer propagates in the lateral direction of the light-emitting layer.

[0440] The method is characterized in that

[0441] When the side of the light-emitting layer that becomes the exciton high density region is the electron injection portion side, the hole blocking layer is provided between the light-emitting layer and the electron injection portion and adjacent to the light-emitting layer.

[0442] When the side of the light-emitting layer that becomes the exciton high density region is the hole injection portion side, the electron blocking layer is provided between the light-emitting layer and the hole injection portion and adjacent to the light-emitting layer.

[0443] The organic electroluminescent element that is the object of the present invention can be set as an organic electroluminescent element in which the light generated in the light-emitting layer propagates in the lateral direction of the light-emitting layer. Here, "lateral direction of the light-emitting layer" refers to the direction along the interface of the light-emitting layer (the direction orthogonal to the thickness direction). The organic electroluminescent element in which light propagates in the lateral direction of the light-emitting layer can be obtained by forming refractive index waveguides and gain waveguides in the element. The refractive index waveguide is formed by constituting at least one layer between the light-emitting layer and the hole injection part and at least one layer between the light-emitting layer and the electron injection part as a low refractive index layer having a refractive index lower than that of the light-emitting layer. For example, at least one layer of the electron transport layer and the hole blocking layer and at least one layer of the electron blocking layer and the hole transport layer can be constituted as a low refractive index layer. In one embodiment of the present invention, the layer adjacent to the electron injection part side of the light-emitting layer and the layer adjacent to the hole injection part side of the light-emitting layer are both low refractive index layers having a refractive index lower than that of the light-emitting layer. In addition, the gain waveguide can be formed by designing the element in such a way that the gain becomes higher in the central part of the lateral light path. For the description of these waveguides, please refer to the description of refractive index waveguide and gain waveguide in the column of <Organic solid semiconductor laser>. In this type of organic electroluminescent element, as opposed to light propagating in the horizontal direction, the migration of holes advancing in the vertical direction is hindered (blocked) in the hole blocking layer. Alternatively, as opposed to light propagating in the horizontal direction, the migration of electrons advancing in the vertical direction is hindered (blocked) in the electron blocking layer. In addition, in the organic electroluminescent element that is the object of the present invention, as long as the light propagates in the horizontal direction in the light-emitting layer, the final light extraction direction can also be set to the vertical direction.

[0444] The organic electroluminescent element targeted in the present invention may be a conventional organic electroluminescent element that mainly emits spontaneous emission light, or an organic electroluminescent element (e.g., an organic solid semiconductor laser) that has an optical resonator that propagates the emitted light within a light-emitting layer and oscillates laser light.

[0445] Regarding the description of the hole injection portion, electron injection portion and light-emitting layer constituting the organic electroluminescent element, the description of the optical resonator provided as needed, and the description of the hole blocking layer or electron blocking layer provided corresponding to the position of the exciton high density region, reference can be made to the corresponding descriptions in the above-mentioned [First Embodiment] and [Second Embodiment] columns. In addition, the organic electroluminescent element as the object of the present invention may also have other layers besides the hole injection portion, electron injection portion, light-emitting layer, hole blocking layer and electron blocking layer. As other layers, an electron transport layer, a hole transport layer and a spacer layer can be listed, and other layers and a substrate may be further provided. Regarding the description of these layers, reference can also be made to the descriptions in the above-mentioned [First Embodiment] and [Second Embodiment] columns.

[0446] The organic electroluminescent element may be the organic solid-state semiconductor laser of the first embodiment or the second embodiment, or may be an organic electroluminescent element obtained by removing the optical resonator from these organic solid-state semiconductor lasers. The organic electroluminescent element used as the subject of the present invention may be an organic electroluminescent element in which light generated in a light-emitting layer propagates laterally along the light-emitting layer.

[0447] In the present invention, a "high exciton density region" can refer to a virtual cross-sectional region perpendicular to the thickness direction, where the exciton density in the light-emitting layer is highest when holes from the hole injection unit and electrons from the electron injection unit are injected into the light-emitting layer, resulting in carrier recombination. The location of the high exciton density region can be determined by simulating the exciton density distribution in the light-emitting layer.

[0448] For example, the Figure 8 In the simulation results, the interface between the hole blocking layer HBL and the light-emitting layer EML, which corresponds to the peak of the exciton density distribution, corresponds to the “exciton high density region”.

[0449] Furthermore, in the present invention, the "side becoming the exciton high density region" can be determined as the hole injection part side of the light-emitting layer when there is an exciton high density region closer to the hole injection part side than the central plane in the thickness direction of the light-emitting layer, and can be determined as the electron injection part side of the light-emitting layer when there is an exciton high density region closer to the electron injection part side than the central plane.

[0450] Therefore, in Figure 8 In the simulation results shown, the electron injection site side is determined to be the "side with a high exciton density," and a hole-blocking layer is provided between the light-emitting layer and the electron injection site, adjacent to the light-emitting layer. Furthermore, if the simulation results show a peak in the exciton density distribution on the hole injection site side of the light-emitting layer, the hole injection site side can be determined to be the "side with a high exciton density," and an electron-blocking layer is provided between the light-emitting layer and the hole injection site, adjacent to the light-emitting layer.

[0451] In an organic electroluminescent element in which the electron injection portion is located on the side of the electron-injection portion of the light-emitting layer and a hole-blocking layer is provided adjacent to the electron-injection portion of the light-emitting layer, holes (+) that migrate from the light-emitting layer are retained at the interface of the light-emitting layer / hole-blocking layer. As a result, carrier recombination occurs in a concentrated manner in a narrow area near the interface, forming a carrier recombination zone RZ with a high exciton density. H In this way, the peak width of the emission spectrum can be reduced.

[0452] On the other hand, in an organic electroluminescent element in which the hole injection portion is located on the side of the exciton high density region and an electron blocking layer is provided at a position adjacent to the hole injection portion of the light-emitting layer, electrons (-) that migrate from the light-emitting layer 24 are retained at the interface of the light-emitting layer / electron blocking layer, thereby concentratedly recombine carriers in a narrow region near the interface to form a carrier recombination region RZ with a high exciton density. H In this way, the peak width of the emission spectrum can be reduced.

[0453] The organic electroluminescent element used in the present invention may be a conventional organic electroluminescent element or an element (e.g., an organic solid-state semiconductor laser) that oscillates laser light by having an optical resonator that propagates emitted light within a light-emitting layer. When the optical resonator is a diffraction grating having grating convex portions and grating concave portions, the position of the hole blocking layer or the electron blocking layer can be set to a position along the flat interface of the light-emitting layer. Thus, a carrier recombination zone RZ is formed along the flat interface. H , which is beneficial to narrowing the peak width of the luminescence spectrum.

[0454] In a preferred embodiment of the present invention, the target organic electroluminescent element has a diffraction grating between the high exciton density region of the light-emitting layer and the hole injection portion, and the hole blocking layer can be provided between the light-emitting layer and the electron injection portion and adjacent to the light-emitting layer.

[0455] In a preferred embodiment of the present invention, the target organic electroluminescent element has a diffraction grating between the high exciton density region of the light-emitting layer and the electron injection part, and the electron blocking layer can be provided between the light-emitting layer and the hole injection part and adjacent to the light-emitting layer.

[0456] <Method for Adjusting the Thickness and Refractive Index of the Spacer Layer in an Organic Electroluminescent Element>

[0457] Next, a method for adjusting the thickness and refractive index of the spacer layer in the organic electroluminescent element of the present invention will be described.

[0458] The organic electroluminescent element targeted by the present invention may include a spacer layer at least one of between the light-emitting layer and the electron injection portion and between the light-emitting layer and the hole injection portion.

[0459] The spacer layer forms a spacer between the light-emitting layer and the electron-injection unit, or between the light-emitting layer and the hole-injection unit. This prevents light from the light-emitting layer from being lost due to surface plasmon polaritons formed on the electrode surfaces of the electron-injection unit or the hole-injection unit, or from absorption or scattering in the electrode. By suppressing light absorption at the electrode, which can lead to significant light loss, the spacer layer effectively lowers the ASE (amplified spontaneous emission) threshold and the laser oscillation threshold.

[0460] As described above, the optical loss suppression effect of the spacer layer depends on its thickness and refractive index. Therefore, adjusting the thickness and refractive index of the spacer layer is crucial to effectively lowering the ASE threshold and the laser oscillation threshold. In view of this, the present invention uses the absorption model represented by the following equation as an indicator for adjusting the thickness and refractive index of the spacer layer.

[0461] I=I0e -αx

[0462] Here, I represents the light intensity after traveling a distance x, I0 represents the initial light intensity, α represents the absorption coefficient of the medium in the electron injection unit (electrode) and the spacer layer, and x represents the distance the light travels through the medium. Here, the absorption coefficient α is expressed by the following formula.

[0463] α=4πk / λ

[0464] Where k is the absorption coefficient of the medium, and n is the complex refractive index expressed by the following formula: * The imaginary part of λ. λ represents the wavelength of light in the medium.

[0465] n * =n+ik

[0466] Where n * represents the complex refractive index, n represents the real refractive index of the medium, k represents the absorption coefficient of the medium, and i represents the imaginary unit.

[0467] The ASE threshold and the laser oscillation threshold are very sensitive to light absorption loss. Therefore, by adjusting the thickness and refractive index of the spacer layer according to this absorption model, an organic electroluminescent element with low light absorption loss and low ASE threshold and laser oscillation threshold can be reliably achieved. The following is a specific description of the method for adjusting the spacer layer of the present invention. In the following description, the method for adjusting the spacer layer (first spacer layer) disposed between the light-emitting layer / electron injection portion is referred to as the first method, and the method for adjusting the spacer layer (second spacer layer) disposed between the light-emitting layer / hole injection portion is referred to as the second method.

[0468] Furthermore, the "ASE threshold" in the present invention is a value obtained by using the excitation intensity at the slope change point of the excitation intensity-light output characteristic measured for a stacked sample without an optical resonator, and the "laser oscillation threshold" in the present invention is a value obtained by using the excitation intensity at the slope change point of the excitation intensity-light output characteristic measured for a stacked sample with an optical resonator.

[0469] [Method 1]

[0470] The first method is a method for adjusting at least one of the thickness and refractive index of a first spacer layer of an organic electroluminescent element, wherein the organic electroluminescent element comprises: a hole injection portion for injecting holes; an electron injection portion for injecting electrons; a light-emitting layer disposed between the hole injection portion and the electron injection portion for causing holes and electrons to recombine to emit light; and a first spacer layer disposed between the light-emitting layer and the electron injection portion.

[0471] This method is characterized in that at least one of the thickness and the refractive index of the first spacer layer is adjusted using an absorption model.

[0472] The organic electroluminescent element used in the first method may be a conventional organic electroluminescent element that mainly emits spontaneous emission light, or an organic electroluminescent element (e.g., an organic solid semiconductor laser) that has an optical resonator that propagates emitted light in a light-emitting layer and oscillates laser light.

[0473] For descriptions of the hole injection unit, electron injection unit, light-emitting layer, and first spacer layer that constitute the organic electroluminescent element, as well as descriptions of the optical resonator provided as needed, please refer to the corresponding descriptions in the columns [First Embodiment] and [Second Embodiment] above. The first spacer layer corresponds to the "spacer layer" in the first embodiment. The material for the first spacer layer is preferably a material with a low refractive index and low light absorption relative to light from the light-emitting layer. TPBi (refractive index n: 1.798 and attenuation coefficient k: 0 relative to the emission wavelength of BSBCz) can be preferably used. Furthermore, the organic electroluminescent element targeted by the present invention may include layers other than the hole injection unit, electron injection unit, light-emitting layer, and first spacer layer. Examples of these other layers include a hole-blocking layer, an electron-blocking layer, an electron-transporting layer, a hole-transporting layer, and a second spacer layer. Further layers and a substrate may also be included. For descriptions of these layers, please refer to the descriptions in the columns [First Embodiment] and [Second Embodiment] above. At least one of the thickness and refractive index of the second spacer layer can be adjusted using the second method described below.

[0474] The organic electroluminescent element may be the organic solid-state semiconductor laser of the first embodiment or the second embodiment, or may be an organic electroluminescent element in which the optical resonator is removed from these organic solid-state semiconductor lasers. In the organic electroluminescent element used as the subject of the present invention, the first spacer layer is an essential layer, and the hole blocking layer and the electron blocking layer are optional. Furthermore, the organic electroluminescent element used as the subject of the present invention may have only one of the hole blocking layer and the electron blocking layer, or may have both.

[0475] The absorption model used in the first method is, for example, an absorption model for a laminate sample formed by sequentially laminating the light-emitting layer, the first spacer layer, and the electron injection portion of each section of the target organic electroluminescent element. Here, at least one (preferably only one) of the thickness and refractive index of the first spacer layer is varied, while the other layers are formed using the same material and thickness as the target organic electroluminescent element.

[0476] Specific examples of the laminated body samples are shown in Figure 3 (a). Figure 3 The laminate sample shown in (a) is a sample formed by sequentially laminating a BSBCz luminescent layer (200 nm), a TPBi spacer layer (×1 nm), and an Ag electron injection portion (100 nm) on a glass substrate. The simulation results of the electric field intensity distribution in the resonance mode of the laminate sample are shown in FIG. Figure 3 (b) Figure 3 (c). Figure 3 (c) Enlarged view Figure 3The circled portion in (b). By providing the first spacer layer (TPBi) and increasing its thickness by X1, the portion of the electric field intensity distribution associated with the electron injection site (Ag) is reduced, thereby suppressing light absorption losses in the electron injection site. Specifically, by using transparent TPBi as a spacer layer in the BSBCz emission wavelength region, the electrode (Ag) is distanced from the light-emitting layer (BSBCx), reducing Ag-induced absorption losses in the electromagnetic waves emitted by the BSBCz. In the present invention, at least one of the thickness and refractive index of the first spacer layer is adjusted according to the absorption model to demonstrate this effect.

[0477] For example, in one embodiment of the present invention, for a stacked sample, the relationship between the thickness of the first spacer layer and the absorption coefficient α of the stacked sample is calculated using an absorption model, and the thickness of the first spacer layer of the element is selected from the relationship within the thickness range of the first spacer layer where the absorption coefficient α is below a set reference threshold.

[0478] Will target Figure 3 The relationship between the thickness of the TPBi spacer layer and the calculated value of the absorption coefficient α and the measured value of the ASE threshold (ASE Eth) for the laminate sample shown in (a) is shown in FIG. Figure 4 Thus, the calculated value of the absorption coefficient α and the measured value of the ASE threshold are highly consistent in their dependence on the thickness of the first spacer layer. Therefore, by selecting the thickness of the first spacer layer of the device from the range of first spacer layer thicknesses where the calculated value of the absorption coefficient α is below a set reference value, an organic electroluminescent device with low light absorption loss and a low ASE threshold, and an organic solid-state semiconductor laser with a low laser oscillation threshold, can be obtained.

[0479] In one embodiment of the present invention, for a stacked sample, the relationship between the refractive index of the first spacer layer and the absorption coefficient α of the stacked sample is calculated using an absorption model, and the refractive index of the first spacer layer of the element is selected from the refractive index range of the first spacer layer whose absorption coefficient is below a set reference threshold value.

[0480] The calculated values ​​of the absorption coefficient α of the laminated body sample and the measured values ​​of the ASE threshold were also confirmed to be highly consistent with respect to the refractive index dependency of the first spacer layer. Therefore, by selecting the refractive index of the first spacer layer of the device from within the refractive index range of the first spacer layer where the calculated value of the absorption coefficient α is below a predetermined reference value, an organic electroluminescent device with minimal light absorption loss and a low ASE threshold, or an organic solid-state semiconductor laser with a low lasing threshold, can be obtained.

[0481] In one embodiment of the present invention, for a stacked body sample further comprising an optical resonator, the relationship between the thickness of the first spacer layer and the absorption coefficient α of the stacked body sample is calculated using an absorption model, and the thickness of the first spacer layer of the element is selected from the range of the thickness of the first spacer layer in which the absorption coefficient is below a set reference threshold value in the relationship.

[0482] The calculated value of the absorption coefficient α of the laminate sample and the measured value of the laser oscillation threshold were confirmed to be highly consistent with each other in terms of the thickness dependence of the first spacer layer. Therefore, by selecting the thickness of the first spacer layer of the device within the range of the first spacer layer thickness where the calculated value of the absorption coefficient α is below a predetermined reference value, an organic solid-state semiconductor laser with low optical absorption loss and a low laser oscillation threshold can be obtained.

[0483] In one embodiment of the present invention, for a stacked body sample further having an optical resonator, the relationship between the refractive index of the first spacer layer and the absorption coefficient α of the stacked body sample is calculated by an absorption model, and the refractive index of the first spacer layer of the element is selected from the refractive index range of the first spacer layer in which the absorption coefficient α is below a set reference value in this relationship.

[0484] The calculated value of the absorption coefficient α of the laminate sample and the measured value of the laser oscillation threshold were also confirmed to be highly consistent with respect to the refractive index dependency of the first spacer layer. Therefore, by selecting the refractive index of the first spacer layer of the element within the refractive index range of the first spacer layer where the calculated value of the absorption coefficient α is below a predetermined reference value, an organic solid-state semiconductor laser with minimal optical absorption loss and a low laser oscillation threshold can be obtained.

[0485] [Method 2]

[0486] The second method is a method for adjusting at least one of the thickness and refractive index of a second spacer layer of an organic electroluminescent element, wherein the organic electroluminescent element comprises: a hole injection portion for injecting holes; an electron injection portion for injecting electrons; a light-emitting layer disposed between the hole injection portion and the electron injection portion for causing holes and electrons to recombine to emit light; and a second spacer layer disposed between the light-emitting layer and the hole injection portion.

[0487] This method is characterized in that at least one of the thickness and the refractive index of the second spacer layer is adjusted using an absorption model.

[0488] For the description of the organic electroluminescent element used as the object in the second method, reference can be made to the description in the column [First Method] above. The organic electroluminescent element used as the object in the second method has a second spacer layer between the light-emitting layer and the hole injection part, and may or may not have a first spacer layer between the light-emitting layer and the electron injection part. That is, the organic electroluminescent element used as the object in the second method of the present invention may have only the second spacer layer among the first and second spacer layers, or may have both the first spacer layer and the second spacer layer. At least one of the thickness and refractive index of the first spacer layer can be adjusted using the first method above. The second spacer layer corresponds to the "spacer layer" of the second embodiment above. The material of the second spacer layer is preferably a material having a low refractive index and low light absorption relative to the light from the light-emitting layer, and NPD (refractive index n: 1.866, attenuation coefficient k: 0 relative to the emission wavelength of BSBCz) can be preferably used.

[0489] The absorption model used in the second method is, for example, an absorption model for a laminate sample formed by sequentially laminating the hole injection portion, the second spacer layer, and the light-emitting layer of each portion of the target organic electroluminescent element. Here, at least one (preferably only one) of the thickness and refractive index of the second spacer layer is varied, while the other layers are formed using the same material and thickness as the target organic electroluminescent element.

[0490] Specific examples of the laminated body samples are shown in Figure 5 (a). Figure 5 The laminate sample shown in (a) is a sample in which an ITO hole injection portion (30 nm), an NPD spacer layer (×2 nm), and a BSBCz light-emitting layer (200 nm) are sequentially laminated on a glass substrate. The simulation results of the electric field intensity distribution of the resonance mode of the laminate sample are shown in FIG. Figure 5 (b) Figure 5 (c). Figure 5 (c) Enlarged view Figure 5 The circled portion of (b). By providing a second spacer layer (NPD) and increasing its thickness by X2, the portion of the electric field intensity distribution associated with the hole injection portion (ITO) is reduced, thereby suppressing light absorption losses in the ITO hole injection portion. By using transparent NPD as a spacer layer in the BSBCz emission wavelength region, the electrode (ITO) is distanced from the light-emitting layer (BSBCz), reducing ITO-induced absorption losses of electromagnetic waves emitted by the BSBCz. In the present invention, at least one of the thickness and refractive index of the second spacer layer is adjusted based on an absorption model to demonstrate this effect.

[0491] For example, in one embodiment of the present invention, the relationship between the thickness of the second spacer layer and the absorption coefficient α of the stacked sample is determined, and the thickness of the second spacer layer of the element is selected from the range of the second spacer layer thickness where the absorption coefficient α is below a set reference threshold value.

[0492] Will target Figure 5 The relationship between the thickness of the NPD spacer layer and the calculated value of the absorption coefficient α and the measured value of the ASE threshold (ASE Eth) for the laminate sample shown in (a) is shown in FIG. Figure 6 Thus, the calculated value of the absorption coefficient α and the measured value of the ASE threshold are highly consistent in their dependence on the thickness of the second spacer layer. Therefore, by selecting the thickness of the second spacer layer of the device from the range of the second spacer layer thickness where the calculated value of the absorption coefficient α is below a set reference value, an organic electroluminescent device with low light absorption loss and a low ASE threshold, and an organic solid-state semiconductor laser with a low laser oscillation threshold, can be obtained.

[0493] In one embodiment of the present invention, for a stacked sample, the relationship between the refractive index of the second spacer layer and the absorption coefficient α of the stacked sample is calculated using an absorption model, and the refractive index of the second spacer layer of the element is selected from the relationship in which the absorption coefficient α is within the refractive index range of the second spacer layer below a set reference threshold.

[0494] The calculated values ​​of the absorption coefficient α of the laminated body sample and the measured values ​​of the ASE threshold were also confirmed to be highly consistent with respect to the refractive index dependency of the second spacer layer. Therefore, by selecting the refractive index of the second spacer layer of the device from within the refractive index range of the second spacer layer where the calculated value of the absorption coefficient α is below a predetermined reference value, an organic electroluminescent device with minimal light absorption loss and a low ASE threshold, or an organic solid-state semiconductor laser with a low lasing threshold, can be obtained.

[0495] In one embodiment of the present invention, for a stacked body sample further having an optical resonator, the relationship between the thickness of the second spacer layer and the absorption coefficient α of the stacked body sample is calculated through an absorption model, and the refractive index of the second spacer layer of the element is selected from the relationship within the thickness range of the second spacer layer where the absorption coefficient α is below a set reference threshold.

[0496] The calculated value of the absorption coefficient α of the laminate sample and the measured value of the laser oscillation threshold were also confirmed to be highly consistent with respect to the thickness dependence of the second spacer layer. Therefore, by selecting the thickness of the second spacer layer in the device from a range where the absorption coefficient α is equal to or less than a predetermined reference value, an organic solid-state semiconductor laser with low optical absorption loss and a low laser oscillation threshold can be manufactured.

[0497] In one embodiment of the present invention, for a stacked body sample further having an optical resonator, the relationship between the refractive index of the second spacer layer and the absorption coefficient α of the stacked body sample is calculated through an absorption model, and the refractive index of the second spacer layer of the element is selected from the refractive index range of the second spacer layer in which the absorption coefficient α is below a set reference value in this relationship.

[0498] The calculated value of the absorption coefficient α of the laminate sample and the measured value of the laser oscillation threshold were also confirmed to be highly consistent with respect to the refractive index dependency of the second spacer layer. Therefore, by selecting the refractive index of the second spacer layer of the element within the refractive index range of the second spacer layer where the calculated value of the absorption coefficient α is below a predetermined reference value, an organic solid-state semiconductor laser with minimal optical absorption loss and a low laser oscillation threshold can be obtained.

[0499] In the first method and the second method, as a reference value for setting the calculated value of the absorption coefficient α, for example, the value of the absorption coefficient α when the ASE threshold or the laser oscillation threshold is sufficiently low can be used.

[0500] Example

[0501] Hereinafter, examples will be given to further specifically describe the features of the present invention. As long as the materials, processing contents, processing sequence, etc. shown below do not depart from the main purpose of the present invention, they can be appropriately changed. Therefore, the scope of the present invention should not be interpreted restrictively due to the specific examples shown below. In addition, regarding the luminescent characteristics of each component, a DC voltage or a rectangular pulse voltage (pulse width: 400ns, repetition frequency: 1kHz) was applied to the component and evaluated using a spectrophotometer (Hamamatsu Photonics KK system: PMA-50), and regarding the current density voltage characteristics, an integrating sphere system (Hamamatsu Photonics KK system: A10094) was used to evaluate at room temperature.

[0502] [1] Fabrication and evaluation of bottom-emitting organic solid-state semiconductor lasers

[0503] (Example 1)

[0504] First, a second-order DFB diffraction grating was formed on a glass substrate having an anode formed thereon with a thickness of 30 nm made of indium tin oxide (ITO) by electron beam lithography in the following procedure.

[0505] After UV ozone treatment was performed on the ITO surface, a SiO2 layer with a thickness of 100 nm was formed by sputtering. Here, the sputtering method was implemented under argon pressure: 0.66 Pa, temperature: 100°C, and RF power: 100 W. After cleaning the surface of the SiO2 layer and performing UV ozone treatment, hexamethyldisilazane (HMDS) was added dropwise and spin-coated at 4000 rpm for 15 seconds, and annealed at 120°C for 120 seconds. Next, a resist solution (Zeon Corporation: ZEP520A-7) was added dropwise, spin-coated at 4000 rpm for 30 seconds, and then fired at 180°C for 240 seconds to form a resist layer with a thickness of 70 nm. The resist layer was irradiated with an electron beam and treated with a developer (Zeon Corporation: ZEDN50) to form a resist mask with a planar shape of a grating. Next, plasma etching using CHF₃ / O₂ as the process gas was performed through the resist mask to remove the portion of the SiO₂ layer not covered by the resist mask, exposing the ITO surface. This formed a second-order DFB diffraction grating. The length of the portion of the grating protrusion that intruded into the light-emitting layer (the intrusion portion) was 70 nm.

[0506] Then, the vacuum evaporation method (vacuum degree 1.5×10 -5 Pa), on an ITO substrate with a DFB diffraction grating formed thereon (DFB substrate), the thin films were stacked in the following order.

[0507] On ITO and DFB diffraction gratings, HATCN was evaporated to a thickness of 10nm to form a hole injection layer, and NPD was evaporated to a thickness of 20nm thereon to form a hole transport layer. Then, BSBCz was evaporated to a thickness of 90nm to form a light-emitting layer. Then, T2T was evaporated to a thickness of 10nm to form a hole blocking layer, and TPBi was evaporated to a thickness of 60nm thereon to form an electron transport layer. After that, LiF was evaporated to a thickness of 1nm, Al was evaporated to a thickness of 1nm thereon, and then Ag was evaporated to a thickness of 100nm to form a cathode, thereby serving as a bottom-emitting organic solid-state semiconductor laser (laser element 1). Finally, the produced organic solid-state semiconductor laser was encapsulated with a glass cover and UV-curing epoxy resin in a nitrogen-filled glove box.

[0508] The energy level diagram of the manufactured laser element 1 is shown in FIG. Figure 7 .exist Figure 7 Here, “HIL” denotes a hole injection layer, “HTL” denotes a hole transport layer, “EML” denotes an emission layer, “HBL” denotes a hole blocking layer, and “ETL” denotes an electron transport layer.

[0509] (Example 2)

[0510] An organic solid-state semiconductor laser (laser element 2) was produced by the same procedure as in Example 1, except that the thickness of each layer was changed as shown in Table 1.

[0511] (Example 3)

[0512] An organic solid-state semiconductor laser (laser element 3) was produced in the same manner as in Example 1 except that the thickness of each layer was changed as shown in Table 1, the electron transport layer was not formed, and the hole blocking layer was formed from TPBi.

[0513] (Example 4)

[0514] An organic solid-state semiconductor laser (laser element 4) was produced in the same manner as in Example 2, except that the light-emitting layer was formed by co-evaporation of BSBCz and CBP. The concentration of BSBCz was set to 5 wt%.

[0515] (Comparative Example 1)

[0516] By stacking various thin films on a DFB substrate produced in the same order as in Example 1 by vacuum evaporation, an organic solid-state semiconductor laser having the same layer structure as the laser element described in WO2018 / 147470 was produced.

[0517] Specifically, Cs and BSBCz were co-evaporated onto the ITO and diffraction grating of the DFB substrate to form a 60nm thick layer. BSBCz was then deposited onto this layer to a thickness of 150nm, forming a light-emitting layer. During the co-evaporation, the BSBCz concentration was set to 20% by weight. Subsequently, MoO3, Ag, and Al were sequentially deposited to thicknesses of 10nm, 10nm, and 90nm to form an anode, which served as an organic solid-state semiconductor laser (comparative laser element 1). This organic solid-state semiconductor laser was packaged using the same procedures as in Example 1.

[0518]

[0519] The results of calculating the exciton density distribution for the laser elements 2 and 3 and the comparative laser element 1 are shown in FIG. Figure 8 .exist Figure 8 In the figure, the horizontal axis represents the distance from the upper surface of the light-emitting layer (the surface on the cathode side), the positive value is the distance from the upper surface to the anode side (the thickness direction of the light-emitting layer), and the negative value is the distance from the upper surface to the cathode side (the thickness direction of the hole blocking layer). Figure 8As shown, in comparative laser element 1, which does not have a hole-blocking layer, the exciton density is uniformly low throughout the entire light-emitting layer, and carrier recombination occurs sparsely throughout the entire light-emitting layer. In contrast, in laser elements 2 and 3, which have hole-blocking layers, the exciton density near the interface between the light-emitting layer and the hole-blocking layer is much higher than in other regions, indicating that carrier recombination occurs intensively near this interface.

[0520] A DC voltage of 5V or 10V was applied to the laser element 1 and the photon band diagram, emission spectrum and angular light intensity distribution were measured from the substrate side. The measurement results at 5V are shown in FIG. Figure 9 (a), the measurement results at 10V are shown in Figure 9 (b) Furthermore, a DC voltage was applied to laser elements 2 to 4 and comparative laser element 1, and the photon band diagram, emission spectrum, and angular light intensity distribution were measured from the substrate side, along with the emission spectrum measured by varying the applied voltage. Figures 10 to 13 Here, the horizontal axis of the angular light intensity distribution (light intensity distribution on the upper side of each figure) represents the light receiving angle when the vertical direction relative to the substrate surface is set to 0°. In addition, the luminous spectrum ( Figure 9 、 Figure 12 The light intensity distribution on the right side of Figure 10 、 Figure 11 、 Figure 13 The light intensity distribution on the right and bottom sides of ) is the light intensity distribution relative to the wavelength measured with the receiving angle set to 0°.

[0521] like Figure 13 As shown in FIG. 1 , in the comparative laser element 1 without a hole blocking layer, two emission peaks with large line widths are observed in the emission spectrum, and multiple broad peaks are also observed in the angular light intensity distribution over a wide angle range. This indicates that the peak wavelength varies with the angle of light reception. On the other hand, as Figure 4 (b) Figures 10 to 12 As shown, in laser elements 1 to 4 equipped with a hole-blocking layer, applying a voltage above the laser oscillation threshold results in a sharp peak with a narrow half-width observed in both the emission spectrum and the angular light intensity distribution. This demonstrates that the provision of a hole-blocking layer reduces both the peak width of the emission spectrum and the peak width of the angular light intensity distribution, improving laser efficiency and monochromaticity. Furthermore, since comparable emission spectra and angular light intensity distributions are observed in laser element 2, which uses a single film of BSBCz in its light-emitting layer, and laser element 4, which uses a doped film of BSBCz, this suggests that the light-emitting layer can be composed solely of the laser oscillating material or as a doped film in which the host material is doped with the laser oscillating material.

[0522] [2] Fabrication and evaluation of dual-emission organic solid-state semiconductor lasers

[0523] (Examples 5 and 6)

[0524] A bottom-emitting organic solid-state semiconductor laser (laser element 5) was produced in the same manner as in Example 2 except that the cathode was changed to the DMD structure shown in Table 2.

[0525] Furthermore, an organic solid-state semiconductor laser (laser element 6) was produced by the same procedure except that the thickness of Ag in the cathode was changed to 20 nm.

[0526] (Examples 7 and 8)

[0527] An organic solid-state semiconductor laser (laser element 7) was produced in the same manner as in Example 5, except that the cathode was changed to the layer structure shown in Table 2.

[0528] An organic solid-state semiconductor laser (laser element 8 ) was produced by the same procedure except that the thickness of Ag in the cathode was changed to 20 nm.

[0529] (Example 9)

[0530] An organic solid-state semiconductor laser (laser element 9) was produced in the same manner as in Example 5, except that the cathode was changed to the layer structure shown in Table 2.

[0531]

[0532] A DC voltage of 40 V was applied to the laser elements 5 to 8, and the photon band diagram, emission spectrum, and angular light intensity distribution were measured from the substrate side. Figures 14 to 17 Furthermore, a DC voltage of 40 V was applied to the laser element 9, and the photon band diagram, emission spectrum, and angular light intensity distribution were measured from the substrate side. Figure 18 (a) The results of measuring the photon band diagram, emission spectrum and angular light intensity distribution from the cathode side are shown in FIG. Figure 18 (b) Here, the horizontal axis of the angular light intensity distribution (the light intensity distribution on the upper side of each figure) represents the angle of light reception when the perpendicular direction relative to the substrate surface is set to 0°. Furthermore, the luminescence spectrum (the light intensity distribution on the right side of each figure) is the light intensity distribution relative to the wavelength measured when the light reception angle is set to 0°.

[0533] like Figures 14 to 18 As shown, in dual-emission laser elements 5 to 9, sharp peaks with narrow half-widths were observed in both the emission spectrum and the angular light intensity distribution. Furthermore, in laser element 9, these narrow peaks were observed on both the substrate and cathode sides. This demonstrates that the hole-blocking layer's effect of narrowing the peaks in the emission spectrum and angular light intensity distribution is also effective in dual-emission devices, demonstrating that a dual-emission organic solid-state semiconductor laser device with excellent laser characteristics can be realized.

[0534] (Example 10)

[0535] On the DFB substrate prepared in the same manner as in Example 1, a vacuum evaporation method was used with a vacuum degree of 1.5×10 -5 Pa stacks various thin films.

[0536] First, on ITO and DFB diffraction gratings, Al was evaporated to a thickness of 1nm and LiF was evaporated thereon to a thickness of 1nm, thereby forming a cathode with an ITO / Al / LiF stacked structure. Then, TPBi was evaporated to a thickness of 80nm to form an electron transport layer, and BSBCz was evaporated thereon to a thickness of 70nm to form a light-emitting layer. Then, NPD was evaporated to a thickness of 20nm to form an electron blocking layer, and HATCN was evaporated thereon to a thickness of 10nm to form a hole injection layer. Moreover, MoO3, Ag, and MoO3 were sequentially evaporated to a thickness of 5nm, 20nm, and 20nm to form an anode of a DMD structure and as an organic solid-state semiconductor laser (laser element 10). The organic solid-state semiconductor laser was packaged in the same order as in Example 1.

[0537] In the laser element 10 , a sharp peak with a narrow half-value width was observed in both the emission spectrum and the light intensity angular distribution.

[0538] [Chemical Formula 10]

[0539]

[0540] Industrial applicability

[0541] The organic solid-state semiconductor laser of the present invention has a small peak width in both the emission spectrum and the angular light intensity distribution, thereby achieving high laser efficiency and excellent monochromaticity, and can be effectively used in various fields utilizing laser light. Therefore, the present invention has high industrial applicability.

[0542] Explanation of symbols

[0543] 11, 21 - hole injection unit, 12 - hole injection layer, 13, 22 - hole transport layer, 14, 24 - light emitting layer, 15 - hole blocking layer, 16, 25 - electron transport layer, 17, 27 - electron injection unit, 18, 28 - diffraction grating of optical resonator, 23 - electron blocking layer, 26 - electron injection layer.

Claims

1. A method for reducing the half width (FWHM) of the emission wavelength peak of the emission spectrum of an organic electroluminescent element, wherein: The organic electroluminescent element comprises: a hole injection portion for injecting holes; an electron injection unit for injecting electrons; and The light-emitting layer allows holes and electrons to recombine and emit light. The light generated in the light-emitting layer propagates in the lateral direction of the light-emitting layer. The method is characterized in that a recombination concentration portion is provided along the lateral direction of the light emitting layer.

2. A method for reducing the half width (FWHM) of the emission wavelength peak of the emission spectrum of an organic electroluminescent element, wherein: The organic electroluminescent element comprises: a hole injection portion for injecting holes; an electron injection unit for injecting electrons; and The light-emitting layer is disposed between the hole injection portion and the electron injection portion, and allows holes and electrons to recombine to emit light. The light generated in the light-emitting layer propagates in the lateral direction of the light-emitting layer. The method is characterized in that When the side of the light-emitting layer that becomes the exciton high density region is the electron injection portion side, the hole blocking layer is provided between the light-emitting layer and the electron injection portion and adjacent to the light-emitting layer. When the side of the light-emitting layer that becomes the exciton high density region is the hole injection portion side, the electron blocking layer is provided between the light-emitting layer and the hole injection portion and adjacent to the light-emitting layer.

3. The method according to claim 2, wherein: A low refractive index layer having a lower refractive index than that of the light-emitting layer is provided between the light-emitting layer and the hole injection portion and between the light-emitting layer and the electron injection portion.

4. The method according to claim 2, wherein: The position of the exciton high density region in the light-emitting layer is determined by simulating the exciton density distribution in the light-emitting layer.

5. The method according to claim 2, characterized in that The organic electroluminescent element further includes an optical resonator that propagates emitted light within the light-emitting layer, and the organic electroluminescent element oscillates laser light.

6. The method according to claim 5, wherein: The optical resonator has a diffraction grating.

7. The method according to claim 6, wherein: The hole blocking layer or the electron blocking layer is formed along a flat interface of the light emitting layer.

8. The method according to claim 6, wherein: The diffraction grating is disposed between the high exciton density region and the hole injection portion or between the high exciton density region and the electron injection portion.

9. The method according to claim 8, wherein When a diffraction grating is provided between the exciton high density region and the hole injection portion, the hole blocking layer is provided between the light emitting layer and the electron injection portion and adjacent to the light emitting layer. When a diffraction grating is provided between the exciton high density region and the electron injection portion, the electron blocking layer is provided between the light emitting layer and the hole injection portion and adjacent to the light emitting layer.

10. The method according to claim 2, characterized in that A spacer layer is provided between at least one of the hole injection portion or the electron injection portion and the exciton high density region. 11 . An organic electroluminescent element, which is manufactured by implementing the method according to claim 1 and has a reduced half-value width (FWHM) of a light emission wavelength peak of a light emission spectrum. 12 . An organic solid-state semiconductor laser manufactured by implementing the method according to claim 5 and having a reduced full width at half maximum (FWHM) of a light-emitting wavelength peak of a light-emitting spectrum.

13. A method for adjusting at least one of the thickness and the refractive index of a first spacer layer of an organic electroluminescent element, The organic electroluminescent element comprises: a hole injection portion for injecting holes; an electron injection unit for injecting electrons; a light-emitting layer disposed between the hole injection portion and the electron injection portion, and causing holes and electrons to recombine to emit light; and a first spacer layer disposed between the light-emitting layer and the electron injection portion; The method is characterized in that at least one of the thickness and the refractive index of the first spacer layer is adjusted using an absorption model.

14. The method according to claim 13, wherein: At least one of the thickness and the refractive index of the first spacer layer of the organic electroluminescent element is adjusted using an absorption model for a laminate sample in which a light-emitting layer, a first spacer layer, and an electron injection portion are sequentially laminated.

15. The method according to claim 14, wherein The laminate sample further includes an optical resonator, and at least one of the thickness and the refractive index of the first spacer layer of the organic electroluminescent element is adjusted using an absorption model for the laminate.

16. The method according to claim 14, wherein For the laminate sample, the relationship between the thickness of the first spacer layer and the absorption coefficient of the laminate sample is calculated using an absorption model, and the thickness of the first spacer layer of the organic electroluminescent element is selected from the thickness range of the first spacer layer whose absorption coefficient is below a set reference threshold in this relationship.

17. The method according to claim 14, wherein: For the stacked body sample, the relationship between the refractive index of the first spacer layer and the absorption coefficient of the stacked body sample is calculated by an absorption model, and the refractive index of the first spacer layer of the organic electroluminescent element is selected from the refractive index range of the first spacer layer whose absorption coefficient is below the set reference threshold in this relationship.

18. A method for adjusting at least one of the thickness and the refractive index of a second spacer layer of an organic electroluminescent element, The organic electroluminescent element comprises: a hole injection portion for injecting holes; an electron injection unit for injecting electrons; a light-emitting layer disposed between the hole injection portion and the electron injection portion, and causing holes and electrons to recombine to emit light; and The second spacer layer is disposed between the light-emitting layer and the hole injection portion. The method is characterized in that at least one of the thickness and the refractive index of the second spacer layer is adjusted using an absorption model.

19. The method according to claim 18, wherein At least one of the thickness and the refractive index of the second spacer layer of the organic electroluminescent element is adjusted using an absorption model for a laminate sample in which a hole injection portion, a second spacer layer, and a light-emitting layer are sequentially laminated.

20. The method according to claim 19, wherein The laminate sample further includes an optical resonator, and at least one of the thickness and the refractive index of the second spacer layer of the organic electroluminescent element is adjusted using an absorption model for the laminate.

21. The method according to claim 19, wherein For the laminate sample, the relationship between the thickness of the second spacer layer and the absorption coefficient of the laminate sample is calculated through an absorption model, and the thickness of the second spacer layer of the organic electroluminescent element is selected from the thickness range of the second spacer layer whose absorption coefficient is below the set reference threshold in this relationship.

22. The method according to claim 19, wherein For the stacked body sample, the relationship between the refractive index of the second spacer layer and the absorption coefficient of the stacked body sample is calculated by an absorption model, and the refractive index of the second spacer layer of the organic electroluminescent element is selected from the refractive index range of the second spacer layer whose absorption coefficient is below the set reference threshold in this relationship. 23 . An organic electroluminescent element produced by carrying out the method according to claim 13 .

24. An organic solid-state semiconductor laser manufactured by carrying out the method according to claim 13.

25. An organic solid-state semiconductor laser manufactured by carrying out the method according to claim 18.

26. An organic solid semiconductor laser, characterized in that: have: a hole injection portion for injecting holes; an electron injection unit for injecting electrons; a light-emitting layer disposed between the hole injection portion and the electron injection portion, and causing holes and electrons to recombine to emit light; and Optical resonator, which allows the emitted light to propagate within the light-emitting layer, A hole blocking layer is provided on the electron injection portion side of the light-emitting layer so as to be adjacent to the light-emitting layer, or an electron blocking layer is provided on the hole injection portion side of the light-emitting layer so as to be adjacent to the light-emitting layer.

27. The organic solid semiconductor laser according to any one of claims 12, 24 to 26, characterized in that A hole blocking layer is provided on the electron injection portion side of the light-emitting layer so as to be adjacent to the light-emitting layer.

28. The organic solid semiconductor laser according to claim 27, characterized in that An absolute value of the HOMO energy of the hole blocking layer is greater than an absolute value of the HOMO energy of the light emitting layer.

29. The organic solid semiconductor laser according to claim 27, wherein An absolute value of the HOMO energy of the hole blocking layer is greater than an absolute value of the HOMO energy of the light emitting layer by 0.1 eV or more.

30. The organic solid semiconductor laser according to claim 27, wherein One or more layers are present between the hole blocking layer and the electron injection portion.

31. The organic solid semiconductor laser according to any one of claims 12, 24 to 26, characterized in that The hole mobility of the light-emitting layer is more than 10 times greater than the electron mobility.

32. The organic solid semiconductor laser according to any one of claims 12, 24 to 26, characterized in that The light emitting layer includes a laser oscillation material and a dopant material.

33. The organic solid semiconductor laser according to any one of claims 12, 24 to 26, characterized in that The thickness of the light-emitting layer is greater than or equal to 10 nm and less than 200 nm.

34. The organic solid semiconductor laser according to any one of claims 12, 24 to 26, characterized in that The half width of the emission angle peak is less than 10 degrees, and the half width of the emission wavelength peak is less than 10 nm.

35. The organic solid semiconductor laser according to any one of claims 12, 24 to 26, wherein At least one of the electron injection portion and the hole injection portion is an electrode having a visible light transmittance of 10% or more.

36. The organic solid semiconductor laser according to any one of claims 12, 24 to 26, wherein The light generated in the light-emitting layer propagates in a lateral direction of the light-emitting layer.

37. The organic solid semiconductor laser according to claim 36, wherein A low refractive index layer having a lower refractive index than that of the light-emitting layer is provided between the light-emitting layer and the hole injection portion and between the light-emitting layer and the electron injection portion.

38. The organic solid semiconductor laser according to claim 26, wherein The optical resonator has a diffraction grating.

39. The organic solid semiconductor laser according to claim 38, wherein The hole blocking layer or the electron blocking layer is formed along a flat interface of the light emitting layer.

40. The organic solid semiconductor laser according to claim 38, wherein The base end of the diffraction grating is arranged at the interface on the hole injection side of the light-emitting layer or at a position closer to the hole injection side than the interface. The hole blocking layer is arranged between the light-emitting layer and the electron injection part and adjacent to the light-emitting layer.

41. The organic solid semiconductor laser according to claim 38, wherein The base end portion of the diffraction grating is arranged at the interface on the electron injection portion side of the light emitting layer or at a position closer to the electron injection portion side than the interface. The electron blocking layer is disposed between the light-emitting layer and the hole injection portion and adjacent to the light-emitting layer.

42. The organic solid semiconductor laser according to any one of claims 12, 24 to 26, characterized in that It is a top-emitting type.

43. The organic solid semiconductor laser according to any one of claims 12, 24 to 26, characterized in that It is a bottom-emitting type.

44. The organic solid semiconductor laser according to any one of claims 12, 24 to 26, characterized in that It is a dual-emitter type.

45. The organic solid semiconductor laser according to any one of claims 12, 24 to 26, characterized in that It is an end-emitting type.

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