Image pickup element and image pickup device

Abstract

To provide an imaging element that can reduce the number of residual electrons.SOLUTION: An imaging element 400 includes a photoelectric conversion element 200 in which an anode 10, a hole transporting buffer layer 40, a photoelectric conversion layer 30, an electron transporting buffer layer 45, and a cathode 20 are stacked sequentially. The photoelectric conversion layer 30 includes a p-type organic semiconductor and an n-type organic semiconductor. The electron transporting buffer layer 45 contains a compound expressed by General Formula (1). The p-type organic semiconductor is a compound expressed by General Formula (2).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an imaging element and an imaging device. [Background technology]

[0002] 2. Description of the Related Art In recent years, photoelectric conversion elements having a photoelectric conversion layer containing an organic semiconductor, imaging elements having the photoelectric conversion elements, and imaging devices having the imaging elements have been developed.

[0003] The photoelectric conversion element has a photoelectric conversion layer and a pair of electrodes (anode and cathode) arranged on either side of the photoelectric conversion layer, which extracts charges (holes and electrons) generated in the photoelectric conversion layer to the outside (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2019 / 0123285 Summary of the Invention [Problem to be solved by the invention]

[0005] However, it is desirable to reduce the number of residual electrons that cause afterimages when capturing moving images using an imaging device.

[0006] Here, the residual electrons are electric charges that are observed as a current that continues to flow even after the light is blocked.

[0007] An object of one embodiment of the present invention is to provide an imaging element in which the number of residual electrons can be reduced. [Means for solving the problem]

[0008] In one aspect of the present invention, an imaging device includes a photoelectric conversion element in which an anode, a hole transporting buffer layer, a photoelectric conversion layer, an electron transporting buffer layer, and a cathode are sequentially stacked, the photoelectric conversion layer including a p-type organic semiconductor and an n-type organic semiconductor, and the electron transporting buffer layer is a compound represented by general formula (1):

[0009] [ka] (In the formula, Ar is a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group; R 1 ~R 4 are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group. The p-type organic semiconductor includes a compound represented by general formula (2):

[0010] [ka] (In the formula, Ar 3 is a substituted or unsubstituted hydrocarbon ring group having two carbonyls or a substituted or unsubstituted heterocyclic group having two carbonyls, R 1 ~R 3 each independently represents a hydrogen atom, a deuterium atom, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, an alkoxy group having 1 to 30 carbon atoms, or an aryl group having 6 to 30 carbon atoms; R 1 and R 2 may be bonded to each other to form a ring, Ar 1 and Ar 2 each independently represents a substituted or unsubstituted arylene group having 6 to 30 carbon atoms or a substituted or unsubstituted heteroarylene group having 3 to 30 carbon atoms; G 1 and G 2 are each independently -(CR d R e ) n -, -Te-, -O-, -S-, -Se-, -NR f -, -SiRg R h -, -SiR gg R hh -,-GeR i R j -,-GeR ii R jj -, -(C(R m )=(C(R n ))-, -(C(R mm )=(C(R nn ))- or a single bond, R d , R e , R f , R g , R h , R i , R j , R m and R n each independently represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 10 carbon atoms; R gg , R hh , R ii , R jj , R mm and R nn are each independently a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or a substituted or unsubstituted aryl group having 6 to 10 carbon atoms, R gg and R hh , R ii and R jj and R mm and R nn At least one of them is bonded to each other to form a ring, and -(CR d R e ) n -In the formula, n is 1 or 2. It is a compound represented by the formula: Effect of the Invention

[0011] According to one embodiment of the present invention, an imaging element capable of reducing the number of residual electrons can be provided. [Brief description of the drawings]

[0012] [Figure 1]1 is a cross-sectional view illustrating a schematic partial structure of a first example of an image sensor according to an embodiment of the present invention. [Diagram 2] 11 is a cross-sectional view illustrating a schematic partial structure of a second example of the image sensor according to the present embodiment. FIG. [Diagram 3] FIG. 11 is a perspective view illustrating a schematic partial structure of a second example of the image sensor according to the present embodiment. [Figure 4] 11 is a cross-sectional view illustrating a schematic partial structure of a third example of the image sensor according to the present embodiment. FIG. [Diagram 5] FIG. 11 is a perspective view illustrating a schematic partial structure of a fourth example of the image sensor according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Next, an embodiment of the present invention will be described with reference to the drawings.

[0014] In the following drawings, thicknesses are enlarged in order to clearly depict multiple layers and regions. In addition, in the drawings, parts that are unnecessary for the description are omitted in order to clearly explain the embodiment of the present invention. Furthermore, the same reference numerals are used throughout the specification to refer to the same or similar components.

[0015] When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes the case where the part is "directly on" the other part, and the case where there is another part between the part and the other part. Conversely, when a part is said to be "directly on" the other part, it means that there is no other part between the part and the other part.

[0016] [Image sensor] FIG. 1 shows a schematic diagram of a partial structure of a first example of an image sensor according to the present embodiment.

[0017] The imaging element 400 includes a photoelectric conversion element 200 and a substrate 310 .

[0018] In the photoelectric conversion element 200, an anode 10, a hole transporting buffer layer 40, a photoelectric conversion layer 30, an electron transporting buffer layer 45, and a cathode 20 are sequentially stacked from the substrate 310 side. Here, the cathode 20 is a light-transmitting electrode. Therefore, when light containing light in the green wavelength region (green light) is incident from the cathode 20 side, the green light is absorbed in the photoelectric conversion layer 30 and photoelectrically converted.

[0019] Examples of materials constituting the transparent electrode include indium tin oxide (ITO), indium zinc oxide (IZO), AZO, FTO, and SnO. 2 , TiO 2 , ZnO 2 Examples of conductive materials include:

[0020] The light-transmitting electrode may be formed of a single layer, or may be formed by laminating a plurality of layers.

[0021] The anode 10 may be either a light-transmitting electrode or a light-opaque electrode.

[0022] Examples of materials constituting the opaque electrode include metals such as aluminum, copper, gold, and silver, and conductive materials such as polysilicon that has been doped with impurities to provide conductivity.

[0023] In forming the anode 10 and cathode 20, various methods can be applied depending on the materials used.

[0024] Examples of methods for forming an ITO electrode include an electron beam method, a sputtering method, a resistance heating deposition method, a chemical reaction method (eg, a sol-gel method), and a method of applying a dispersion of indium tin oxide.

[0025] When the anode 10 and the cathode 20 are formed, they may be subjected to a treatment such as a UV-ozone treatment or a plasma treatment.

[0026] Here, the anode 10 is an electrode that collects holes from among the charges generated in the photoelectric conversion layer 30. The cathode 20 is an electrode that collects electrons from among the charges generated in the photoelectric conversion layer 30.

[0027] By applying a bias voltage between the anode 10 and the cathode 20 , of the charges generated in the photoelectric conversion layer 30 , holes can be moved to the anode 10 and electrons can be moved to the cathode 20 .

[0028] Here, the imaging element 400 converts and reads out an electrical signal according to the amount of holes that have moved to the anode 10. This makes it possible to convert an optical signal into an electrical signal and extract it.

[0029] The electron transporting buffer layer 45 suppresses the injection of holes from the cathode 20 to the photoelectric conversion layer 30 , and also inhibits the movement of holes generated in the photoelectric conversion layer 30 to the cathode 20 .

[0030] The electron transporting buffer layer 45 is formed of a compound represented by the general formula (1):

[0031] [ka] (In the formula, Ar is a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group; R 1 ~R 4 are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group. The compound includes a compound represented by the formula:

[0032] Here, since the compound represented by general formula (1) has a planar structure, it is considered that the compound is stacked inside the electron transporting buffer layer 45, thereby increasing the mobility of electrons in the out-of-plane direction, and as a result, the number of residual electrons that cause afterimages when capturing moving images is reduced.

[0033] Ar, R1 ~R 4 The aryl group in is a monocyclic, non-fused polycyclic or fused polycyclic aryl group.

[0034] Examples of the monocyclic aryl group include a phenyl group.

[0035] Examples of the non-condensed polycyclic aryl group include a biphenyl group, a terphenyl group, a quaterphenyl group, a quinquephenyl group, a sexiphenyl group, a fluoranthenyl group, and a triphenylenyl group.

[0036] Examples of the condensed polycyclic aryl group include a naphthyl group, anthryl group, phenanthryl group, fluorenyl group, indenyl group, pyrenyl group, acetonaphthenyl group, bisphenylfluorenyl group, and 9-(9-fluorenyl)fluorenyl group.

[0037] The monocyclic, non-condensed polycyclic or condensed polycyclic aryl group preferably has 6 to 50 ring carbon atoms, and more preferably has 6 to 40 ring carbon atoms.

[0038] Ar, R 1 ~R 4 The heteroaryl group in is a monocyclic or polycyclic heteroaryl group.

[0039] Examples of the monocyclic heteroaryl group include a pyrrolyl group, an imidazolyl group, a pyrazolyl group, an oxazolyl group, an isoxazolyl group, an oxadiazolyl group, a thiazolyl group, a furanyl group, a pyranyl group, a thienyl group, a pyridyl group, a pyrazyl group, a pyrimidinyl group, a pyridazinyl group, a triazinyl group, a quinolyl group, and an isoquinolyl group.

[0040] Examples of polycyclic heteroaryl groups include a benzo(pyridyl)furanyl group, a benzofuranyl group, a benzothienyl group, an indolyl group, a carbazolyl group, a carbolinyl group, a phenanthridinyl group, an acridinyl group, a perimidinyl group, a phenanthrolinyl group, a benzoxazolyl group, a benzothiazolyl group, a quinoxalyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, and a dibenzothienyl group.

[0041] The monocyclic or polycyclic heteroaryl group preferably has 5 to 50 ring carbon atoms, and more preferably has 5 to 30 ring carbon atoms.

[0042] R 1 ~R 4 The alkyl group in the formula (I) is a linear, branched or cyclic alkyl group.

[0043] Examples of the linear alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an octyl group, a decyl group, and a pentadecyl group.

[0044] An example of the branched alkyl group is a t-butyl group.

[0045] Examples of the cyclic alkyl group include a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group.

[0046] The linear or branched alkyl group preferably has 1-20 carbon atoms, and more preferably has 1-10 carbon atoms.

[0047] The cyclic alkyl group preferably has 3-20 carbon atoms, and more preferably has 3-12 carbon atoms.

[0048] Ar, R 1 ~R 4Examples of the substituent in the above formula include a cyano group, a silyl group, a mono-(di- or tri-)alkylsilyl group having 1 to 10 carbon atoms, a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms, a linear or branched alkoxy group having 1 to 10 carbon atoms, an aryl group having 6 to 15 ring carbon atoms, an aryloxy group having 6 to 15 ring carbon atoms, an arylcarbonyl group having 6 to 15 ring carbon atoms, a heterocyclyl group having 3 to 32 ring carbon atoms, a mono-(or di-)alkylamino group having 1 to 10 carbon atoms, and a mono-(or di-)arylamino group having 6 to 15 ring carbon atoms.

[0049] Specific examples of the compound represented by general formula (1) are shown below.

[0050] [ka] Among these, 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (hereinafter referred to as TPBi) is preferable in terms of the number of residual electrons in the imaging element 400.

[0051] Here, TPBi has the chemical formula

[0052] [ka] It is a compound represented by the formula:

[0053] The thickness of the electron transporting buffer layer 45 is preferably 1.5 nm or more and less than 10 nm. When the thickness of the electron transporting buffer layer 45 is 1.5 nm or more and less than 10 nm, the photoelectric conversion efficiency of the image sensor 400 is improved.

[0054] The photoelectric conversion layer 30 includes a p-type organic semiconductor and an n-type organic semiconductor.

[0055] When green light is incident on the photoelectric conversion layer 30, excitons are generated. The excitons are separated into holes and electrons, and then the holes move to the anode 10 and the electrons move to the cathode 20. As a result, a current flows in the photoelectric conversion element 200.

[0056] The p-type organic semiconductor is represented by the general formula (2):

[0057] [ka] (In the formula, Ar 3 is a substituted or unsubstituted hydrocarbon ring group having two carbonyls or a substituted or unsubstituted heterocyclic group having two carbonyls, R 1 ~R 3 each independently represents a hydrogen atom, a deuterium atom, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, an alkoxy group having 1 to 30 carbon atoms, or an aryl group having 6 to 30 carbon atoms; R 1 and R 2 may be bonded to each other to form a ring, Ar 1 and Ar 2 each independently represents a substituted or unsubstituted arylene group having 6 to 30 carbon atoms or a substituted or unsubstituted heteroarylene group having 3 to 30 carbon atoms; G 1 and G 2 are each independently -(CR d R e ) n -, -Te-, -O-, -S-, -Se-, -NR f -, -SiR g R h -, -SiR gg R hh -,-GeR i R j -,-GeR ii R jj -, -(C(R m )=(C(R n ))-, -(C(R mm )=(C(R nn ))- or a single bond, R d , R e , R f , R g, R h , R i , R j , R m and R n each independently represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 10 carbon atoms; R gg , R hh , R ii , R jj , R mm and R nn are each independently a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or a substituted or unsubstituted aryl group having 6 to 10 carbon atoms, R gg and R hh , R ii and R jj and R mm and R nn At least one of them is bonded to each other to form a ring, and -(CR d R e ) n -In the formula, n is 1 or 2. It is a compound represented by the following formula (see Patent Document 1).

[0058] Specific examples of the compound represented by formula (2) are shown below.

[0059] [ka]

[0060] [ka]

[0061] [ka]

[0062] [ka]

[0063] [ka]

[0064] [ka]

[0065] [ka]

[0066] [ka]

[0067] [ka]

[0068] [ka] Among these, 5-((5-(10,10-dimethyldibenzo[b,e][1,4]azasilin-5(10H)-yl)tellurophen-2-yl)methylene)-1,3-dimethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione (hereinafter referred to as GDP1) is preferred in terms of photoelectric conversion efficiency of the imaging element 400.

[0069] Here, GDP1 has the chemical formula

[0070] [ka] It is a compound represented by the formula:

[0071] The n-type organic semiconductor is not particularly limited as long as it can form a pn junction with the p-type organic semiconductor, but examples thereof include subphthalocyanine, fullerene and its derivatives, thiophene and its derivatives, etc., and two or more of them may be used in combination. Among these, fullerene and / or fullerene derivatives are preferred in terms of the photoelectric conversion efficiency of the photoelectric conversion element 200.

[0072] As fullerenes, for example, C 50 Fullerene, C 60 Fullerene, C 70 Fullerene, C 76 Fullerene, C 78 Fullerene, C 80 Fullerene, C 82 Fullerene, C 84 Fullerene, C 90 Fullerene, C 96 Fullerene, C 240 Fullerene, C 540 Examples include fullerene.

[0073] In the case of a fullerene derivative, the fullerene is substituted with a substituent.

[0074] Examples of the substituent include an alkyl group, an aryl group, and a heterocyclic group.

[0075] The alkyl group may be a straight-chain, branched or cyclic alkyl group.

[0076] Examples of the linear alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an octyl group, a decyl group, and a pentadecyl group.

[0077] An example of the branched alkyl group is a t-butyl group.

[0078] Examples of the cyclic alkyl group include a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group.

[0079] The linear or branched alkyl group preferably has 1-20 carbon atoms, and more preferably has 1-10 carbon atoms.

[0080] The cyclic alkyl group preferably has 3-20 carbon atoms, and more preferably has 3-12 carbon atoms.

[0081] The aryl group is a monocyclic, non-fused polycyclic or fused polycyclic aryl group.

[0082] Examples of the monocyclic aryl group include a phenyl group.

[0083] Examples of the non-condensed polycyclic aryl group include a biphenyl group, a terphenyl group, a quaterphenyl group, a quinquephenyl group, a sexiphenyl group, a fluoranthenyl group, and a triphenylenyl group.

[0084] Examples of the condensed polycyclic aryl group include a naphthyl group, anthryl group, phenanthryl group, fluorenyl group, indenyl group, pyrenyl group, acetonaphthenyl group, bisphenylfluorenyl group, and 9-(9-fluorenyl)fluorenyl group.

[0085] The monocyclic, non-condensed polycyclic or condensed polycyclic aryl group preferably has 6 to 50 ring carbon atoms, and more preferably has 6 to 40 ring carbon atoms.

[0086] The heterocyclic group is a monocyclic or polycyclic heterocyclic group.

[0087] Examples of the monocyclic heterocyclic group include a pyrrolyl group, an imidazolyl group, a pyrazolyl group, an oxazolyl group, an isoxazolyl group, an oxadiazolyl group, a thiazolyl group, a furanyl group, a pyranyl group, a thienyl group, a pyridyl group, a pyrazyl group, a pyrimidinyl group, a pyridazinyl group, a triazinyl group, a quinolyl group, and an isoquinolyl group.

[0088] Examples of polycyclic heterocyclic groups include a benzo(pyridyl)furanyl group, a benzofuranyl group, a benzothienyl group, an indolyl group, a carbazolyl group, a carbolinyl group, a phenanthridinyl group, an acridinyl group, a perimidinyl group, a phenanthrolinyl group, a benzoxazolyl group, a benzothiazolyl group, a quinoxalyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, and a dibenzothienyl group.

[0089] The monocyclic or polycyclic heterocyclic group preferably has 5 to 50 ring carbon atoms, and more preferably has 5 to 30 ring carbon atoms.

[0090] The photoelectric conversion layer 30 may be formed of a single layer, or may be formed by laminating a plurality of layers.

[0091] An example of the photoelectric conversion layer 30 formed as a single layer is an intrinsic semiconductor layer.

[0092] Examples of the layered structure of the photoelectric conversion layer 30 in which multiple layers are stacked include a p-type semiconductor layer / intrinsic semiconductor layer, an intrinsic semiconductor layer / n-type semiconductor layer, a p-type semiconductor layer / intrinsic semiconductor layer / n-type semiconductor layer, and a p-type semiconductor layer / n-type semiconductor layer.

[0093] Here, the intrinsic semiconductor layer includes a p-type organic semiconductor and an n-type organic semiconductor, the p-type semiconductor layer includes a p-type organic semiconductor, and the n-type semiconductor layer includes an n-type organic semiconductor.

[0094] The volume ratio of the p-type organic semiconductor to the n-type organic semiconductor in the intrinsic semiconductor layer is preferably 0.01 to 100, and more preferably 0.02 to 95. This improves the photoelectric conversion efficiency of the photoelectric conversion element 200.

[0095] The thickness of the photoelectric conversion layer 30 is preferably 1 nm to 800 nm, and more preferably 5 nm to 500 nm, so that the photoelectric conversion efficiency of the photoelectric conversion element 200 is improved.

[0096] The photoelectric conversion layer 30 is preferably formed by a dry film formation method, more preferably by a resistance heating deposition method, but may be formed by a wet film formation method.

[0097] An example of the dry film formation method is a vacuum deposition method.

[0098] Specific examples of the vacuum deposition method include an electron beam method, a sputtering method, and a resistance heating deposition method.

[0099] The wet film forming method may be, for example, a solution coating method.

[0100] Examples of the solution application method include casting, spin coating, dip coating, blade coating, wire bar coating, spray coating, inkjet printing, screen printing, offset printing, and letterpress printing.

[0101] Specific examples of the patterning method when the photoelectric conversion layer 30 needs to be patterned include a resist etching method and a laser removal method.

[0102] The hole transporting buffer layer 40 suppresses the injection of electrons from the anode 10 to the photoelectric conversion layer 30 , and inhibits the movement of electrons generated in the photoelectric conversion layer 30 to the anode 10 .

[0103] Examples of materials constituting the hole transport buffer layer 40 include 4,4'-bis[N-naphthyl-N-phenylamino]biphenyl (α-NPD), N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD), 2-TNATA, 4,4',4"-tris(N-(3-methyl)N-phenylamino)triphenylamine (MTDATA), 4,4',4"-tris[2-naphthyl(phenyl)amino]triphenylamine (2-TNATA), 9,9'-(9,9,9',9'-tetramethyl-9H,9'H-[2,2'-bifluorene]-7,7'-diyl)bis(3,6-dimethyl-9H-carbazole) (hereinafter referred to as EB1), and two or more of them may be used in combination. Among these, EB1 is preferable in terms of reducing the dark current value of the image sensor 400 and heat resistance.

[0104] Here, EB1 is a compound represented by the formula

[0105] [ka] It is a compound represented by the formula:

[0106] Instead of the photoelectric conversion element 200, a photoelectric conversion element in which a cathode 20, an electron transporting buffer layer 45, a photoelectric conversion layer 30, a hole transporting buffer layer 40, and an anode 10 are laminated in this order from the substrate 310 side may be used. In this case, the anode 10 is a light-transmitting electrode, and the cathode 20 may be either a light-transmitting electrode or a non-light-transmitting electrode.

[0107] The substrate 310 is a silicon substrate on which a transfer transistor and a charge storage location 55 are integrated. Here, the charge storage location 55 is electrically connected to the photoelectric conversion element 100, and information in the charge storage location 55 is transferred by the transfer transistor.

[0108] Metal wiring and pads are provided on the substrate 310.

[0109] The material for forming the metal wiring and pads is not particularly limited as long as it is possible to reduce signal delay, but examples of the material include metals with low resistivity such as aluminum, copper, silver, and alloys of these.

[0110] An insulating layer 80 is formed between the photoelectric conversion element 200 and the substrate 310 .

[0111] Examples of materials constituting the insulating layer 80 include inorganic insulating substances such as silicon oxide and silicon nitride, and materials with low relative dielectric constants (low-k materials) such as SiC, SiCOH, SiCO, and SiOF.

[0112] The insulating layer 80 has contact holes that expose the pads and through holes 85 that expose the charge storage locations 55 .

[0113] A bandpass filter that transmits only visible light may be provided on the photoelectric conversion element 200 .

[0114] 2 and 3 show schematic diagrams of a partial structure of a second example of the image sensor of this embodiment.

[0115] The imaging element 600 includes a substrate 310, a lower insulating layer 60, a color filter layer 70, an (upper) insulating layer 80, and a (first) photoelectric conversion element 200.

[0116] The substrate 310 is a silicon substrate on which a second photosensitive element 50B that senses light in the blue wavelength region (blue light), a third photosensitive element 50R that senses light in the red wavelength region (red light), a charge storage location 55, and a transfer transistor are integrated, where the second photosensitive element 50B and the third photosensitive element 50R are silicon photodiodes.

[0117] The (first) photoelectric conversion element 200 is disposed on the second photosensitive element 50B and the third photosensitive element 50R and selectively absorbs green light. The charge storage location 55 is electrically connected to the (first) photoelectric conversion element 200. The (first) photoelectric conversion element 200 may be disposed above the second photosensitive element 50B or the third photosensitive element 50R.

[0118] The color filter layer 70 is formed on the second photosensitive element 50B and includes a blue filter 70B that selectively transmits blue light, and a red filter 70R that is formed on the third photosensitive element 50R and selectively transmits red light.

[0119] In addition, in Figure 3, B and R roughly indicate areas where the second photosensitive element 50B and the third photosensitive element 50R sense blue light and red light, respectively, and G roughly indicates an area where the (first) photoelectric conversion element 200 selectively absorbs green light.

[0120] The second photosensitive element 50B and the third photosensitive element 50R sense blue light and red light, respectively, and the sensed information is transferred by the transfer transistor. Also, the information in the charge storage location 55 is transferred by the transfer transistor.

[0121] Metal traces and pads are provided on the substrate 310, but may also be provided underneath the second photosensitive element 50B, the third photosensitive element 50R and the charge storage location 55.

[0122] A lower insulating layer 60 is formed on the substrate 310 .

[0123] The lower insulating layer 60 may be made of the same material as the insulating layer 80 .

[0124] A color filter layer 70 is formed on the lower insulating layer 60 .

[0125] An (upper) insulating layer 80 is formed on the color filter layer 70 in order to remove steps caused by the color filter layer 70 and to flatten the surface.

[0126] The (top) insulating layer 80 and the bottom insulating layer 60 are formed with contact holes exposing the pads and through holes 85 exposing the charge storage locations 55 .

[0127] On the (upper) insulating layer 80, a (first) photoelectric conversion element 200 is formed.

[0128] As described above, the (first) photoelectric conversion element 200 includes the anode 10, the hole transporting buffer layer 40, the photoelectric conversion layer 30, the electron transporting buffer layer 45, and the cathode 20, which are stacked in this order from the substrate 310 side. Here, the anode 10 and the cathode 20 are light-transmitting electrodes capable of transmitting visible light. Therefore, when light including visible light is incident from the cathode 20 side, the green light is absorbed in the photoelectric conversion layer 30 and photoelectrically converted. On the other hand, the light not absorbed in the photoelectric conversion layer 30 is transmitted through the hole transporting buffer layer 40, the anode 10, and the blue filter 70B (or the red filter 70R), and then sensed by the second photosensitive element 50B (or the third photosensitive element 50R).

[0129] In addition, a bandpass filter that transmits only visible light may be provided on the (first) photoelectric conversion element 200.

[0130] FIG. 4 shows a third example of the imaging element of this embodiment.

[0131] Similar to the imaging element 600, the imaging element 800 comprises a substrate 310, an insulating layer 80, and a (first) photoelectric conversion element 200, with a second photosensitive element 50B, a third photosensitive element 50R, a charge storage location 55, and a transmission transistor integrated on the substrate 310.

[0132] On the other hand, the imaging element 800 differs from the imaging element 600 in that the second photosensitive element 50B and the third photosensitive element 50R are stacked in a direction perpendicular to the surface of the substrate 310, and the color filter layer 70 is omitted.

[0133] The second photosensitive element 50B and the third photosensitive element 50R sense blue light and red light, respectively, depending on the stack depth.

[0134] The imaging element 800 can be made compact because the second photosensitive element 50B, the third photosensitive element 50R, and the (first) photoelectric conversion element 200 are stacked.

[0135] Instead of integrating the second photosensitive element 50B and the third photosensitive element 50R on the substrate 310, a second photoelectric conversion element that selectively absorbs blue light and a third photoelectric conversion element that selectively absorbs red light may be disposed on the substrate 310 to stack the (first) photoelectric conversion elements (see FIG. 5). This improves the sensitivity of the imaging element and reduces crosstalk.

[0136] Here, G, B, and R respectively roughly indicate an area where the (first) photoelectric conversion element 200 selectively absorbs green light, an area where the second photoelectric conversion element selectively absorbs blue light, and an area where the third photoelectric conversion element selectively absorbs red light.

[0137] The second photoelectric conversion element has a photoelectric conversion layer between an anode and a cathode, the photoelectric conversion layer containing a known organic semiconductor that selectively absorbs blue light, and may further have a hole transporting buffer layer and / or an electron transporting buffer layer formed thereon, as necessary.

[0138] The third photoelectric conversion element has a photoelectric conversion layer between an anode and a cathode, the photoelectric conversion layer containing a known organic semiconductor that selectively absorbs red light, and may further have a hole transporting buffer layer and / or an electron transporting buffer layer formed thereon, as necessary.

[0139] The order in which the (first) photoelectric conversion element 200, the second photoelectric conversion element, and the third photoelectric conversion element are stacked is not particularly limited.

[0140] The imaging device of this embodiment can be applied to various imaging devices such as mobile phones, digital cameras, and digital videos. EXAMPLES

[0141] Examples of the present invention will be described below, however, the technical scope of the present invention is not limited to only the following examples.

[0142] [Example 1] A hole transport buffer layer was formed by depositing EB1 to a thickness of 5 nm on a glass substrate with an ITO film having a thickness of 100 nm by resistance heating deposition. Next, GDP1 as a p-type organic semiconductor and fullerene C as an n-type organic semiconductor were deposited by resistance heating deposition. 60 A photoelectric conversion layer was formed by depositing TPBi to a thickness of 100 nm and a p / n ratio of 1. Next, a hole transport buffer layer was formed by depositing TPBi to a thickness of 1.5 nm by resistance heating deposition. Furthermore, an ITO film was deposited to a thickness of 10 nm by high frequency magnetron sputtering to obtain a photoelectric conversion element.

[0143] The degree of vacuum in the above vacuum processes was 4×10 -4 Pa or less.

[0144] [Examples 2 to 4] Photoelectric conversion elements were obtained in the same manner as in Example 1, except that TPBi was formed so that the thicknesses of the hole transporting buffer layers were 2.5 nm, 5 nm, and 10 nm, respectively.

[0145] [Comparative Examples 1 to 3] Photoelectric conversion elements were obtained in the same manner as in Examples 2 to 4, except that dipyrazino[2,3-F:2′,3′-H]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (hereinafter referred to as HAT-CN) was used instead of TPBi.

[0146] Here, HAT-CN has the chemical formula

[0147] [ka] It is a compound represented by the formula:

[0148] [Comparative Examples 4 to 6] Photoelectric conversion elements were obtained in the same manner as in Examples 2 to 4, except that 1,3-bis[5-(4-tert-butylphenyl)-2-[1,3,4]oxadiazolyl]benzene (hereinafter referred to as OXD-7) was used instead of TPBi.

[0149] Here, OXD-7 has the chemical formula

[0150] [ka] It is a compound represented by the formula:

[0151] Next, the residual electron number and IPCE of the photoelectric conversion element were evaluated.

[0152] [Residual electron count of photoelectric conversion element, IPCE] The photoelectric conversion element was transported to a glove box where the moisture and oxygen contents were kept below 1 ppm without being exposed to the atmosphere.The photoelectric conversion element was then sealed in a glass sealing can with a UV-curable resin and a moisture absorbent, and then heat-treated at 180°C for 3 hours.

[0153] Using an IPCE measurement system (manufactured by Mac Science), a negative bias of 3 V was applied to the ITO-coated glass substrate side of the photoelectric conversion element, and the number of residual electrons [electrons / 33 ms] after the device was irradiated with visible light at an illuminance of 5000 lx and the screen was turned dark was measured, as well as the external quantum efficiency (IPCE) at the maximum value of the photoelectric conversion efficiency for light with wavelengths of 500 nm to 720 nm.

[0154] Next, the image lag characteristics of the imaging device were evaluated.

[0155] [Afterimage characteristics] After applying the above photoelectric conversion element to an imaging device, a moving image was captured, and the presence or absence of an afterimage was visually evaluated.

[0156] The criteria for judging the afterimage characteristics are as follows:

[0157] ○: When an object is photographed at 30,000 lux, no afterimage is visible. △: No afterimage is visible when photographing an object at 10,000 lux, but an afterimage is visible when photographing an object at 30,000 lux ×: When an afterimage is visible when photographing an object at 10,000 lux Table 1 shows the evaluation results of the number of residual electrons in the photoelectric conversion element, IPCE, and image lag characteristics of the imaging device.

[0158] [Table 1] It can be seen from Table 1 that the photoelectric conversion elements of Examples 1 to 4 have a small number of residual electrons, and the imaging devices having the photoelectric conversion elements of Examples 1 to 4 have excellent afterimage characteristics. In addition, the photoelectric conversion elements of Examples 1 to 4 have high IPCE.

[0159] In contrast, the photoelectric conversion elements of Comparative Examples 1 to 6 have a large number of residual electrons because the electron transport buffer layer does not contain the compound represented by general formula (1), and the imaging devices having the photoelectric conversion elements of Comparative Examples 1 to 6 have poor image retention characteristics. [Explanation of symbols]

[0160] 10 Anode 20 Cathode 30 Photoelectric conversion layer 40 Hole transport buffer layer 45 Electron transport buffer layer 50B Second photosensitive element 50R Third photosensitive element 70 Color filter layer 70B Blue filter 70R Red Filter 200 (first) photoelectric conversion element 400, 600, 800 image sensor

Claims

1. The photoelectric conversion element includes an anode, a hole transporting buffer layer, a photoelectric conversion layer, an electron transporting buffer layer, and a cathode, which are sequentially stacked on top of each other; the photoelectric conversion layer includes a p-type organic semiconductor and an n-type organic semiconductor, the n-type organic semiconductor is a fullerene and / or a fullerene derivative; The electron transporting buffer layer is formed of a compound represented by the general formula (1) 【Chemistry 1】 (In the formula, Ar is a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group; R １ ~R ４ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group. The compound includes a compound represented by The p-type organic semiconductor is represented by the general formula (2): 【Chemistry 2】 (In the formula, Ar ３ is a substituted or unsubstituted hydrocarbon ring group having two carbonyls or a substituted or unsubstituted heterocyclic group having two carbonyls, R １ ~R ３ are each independently a hydrogen atom, a deuterium atom, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, an alkoxy group having 1 to 30 carbon atoms, or an aryl group having 6 to 30 carbon atoms; R １ and R ２ may be bonded to each other to form a ring, Ar １ and Ar ２ each independently represents a substituted or unsubstituted arylene group having 6 to 30 carbon atoms or a substituted or unsubstituted heteroarylene group having 3 to 30 carbon atoms; １ and G ２ Each independently represents -(CR ｄ R ｅ ) ｎ -, -Te-, -O-, -S-, -Se-, -NR ｆ --, --SiR ｇ R ｈ --, --SiR ｇｇ R ｈｈ -, -GeR ｉ R ｊ -, -GeR ｉｉ R ｊｊ -, -(C(R ｍ ) = C(R ｎ ))-, -(C(R ｍｍ ) = C(R ｎｎ ))- or a single bond, R ｄ , R ｅ , R ｆ , R ｇ , R ｈ , R ｉ , R ｊ , R ｍ and R ｎ are each independently a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 10 carbon atoms; R ｇｇ , R ｈｈ , R ｉｉ , R ｊｊ , R ｍｍ and R ｎｎ are each independently a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or a substituted or unsubstituted aryl group having 6 to 10 carbon atoms; R ｇｇ and R ｈｈ , R ｉｉ and R ｊｊ and R ｍｍ and R ｎｎ At least one of -(CR ｄ R ｅ ) ｎ In -, n is 1 or 2. An imaging element which is a compound represented by the formula:

2. 2. The image sensor according to claim 1, wherein the compound represented by the general formula (1) is 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene.

3. The image sensor according to claim 1 , wherein the electron transporting buffer layer has a thickness of 1.5 nm or more and less than 10 nm.

4. a substrate on which a second photosensitive element sensitive to light in the blue wavelength region and a third photosensitive element sensitive to light in the red wavelength region are integrated; 4. The imaging element according to claim 1, wherein the photoelectric conversion element is a first photoelectric conversion element arranged on the second photosensitive element and / or the third photosensitive element and selectively absorbs light in the green wavelength region.

5. The imaging device according to claim 4 , wherein the second photosensitive element and the third photosensitive element are stacked in a direction perpendicular to a surface of the substrate.

6. A color filter layer is further provided between the substrate and the first photoelectric conversion element, the color filter layer includes a blue filter that selectively transmits light in a blue wavelength region and a red filter that selectively transmits light in a red wavelength region; the blue filter is formed on the second photosensitive element; The imaging device according to claim 4 , wherein the red filter is formed on the third photosensitive element.

7. the photoelectric conversion element is a first photoelectric conversion element that selectively absorbs light in a green wavelength region, 4. The imaging element according to claim 1, wherein the first photoelectric conversion element, a second photoelectric conversion element that selectively absorbs light in the blue wavelength region, and a third photoelectric conversion element that selectively absorbs light in the red wavelength region are stacked.

8. An imaging device comprising the imaging element according to claim 1 .

9. In the general formula (2), G １ is -(CR ｄ R ｅ ) ｎ -, -O-, -S-, -Se-, -NR ｆ --, --SiR ｇ R ｈ --, --SiR ｇｇ R ｈｈ -, -GeR ｉ R ｊ -, -GeR ｉｉ R ｊｊ -, -(C(R ｍ ) = C(R ｎ ))-, -(C(R ｍｍ ) = C(R ｎｎ ))- or a single bond, R ｄ , R ｅ , R ｆ , R ｇ , R ｈ , R ｉ , R ｊ , R ｍ and R ｎ are each independently a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 10 carbon atoms; R ｇｇ , R ｈｈ , R ｉｉ , R ｊｊ , R ｍｍ and R ｎｎ are each independently a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or a substituted or unsubstituted aryl group having 6 to 10 carbon atoms; R ｇｇ and R ｈｈ , R ｉｉ and R ｊｊ and R ｍｍ and R ｎｎ At least one of -(CR ｄ R ｅ ) ｎ The imaging device according to claim 1 , wherein n in - is 1 or 2.

10. In the general formula (1), Ar is a substituted aryl group or a substituted or unsubstituted heteroaryl group. R １ ~R ４ The image sensor according to claim 1 , wherein at least one of the groups is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.

Images