A homojunction organic electroluminescent diode and a preparation method and application thereof

Abstract

The application discloses a homojunction organic electroluminescent diode and a preparation method and application thereof. The composition of the homojunction organic electroluminescent diode comprises a substrate, a bottom electrode, a first light-emitting unit, a charge generation layer, a second light-emitting unit and a top electrode which are sequentially arranged in layers, the composition of the first light-emitting unit comprises an electron injection layer, a first electron transport layer and a first light-emitting layer, the composition of the charge generation layer comprises a hole transport layer, a first hole injection layer, a metal layer and a second electron transport layer, the composition of the second light-emitting unit comprises a second light-emitting layer and a second hole injection layer, and the host materials of the first electron transport layer, the first light-emitting layer, the hole transport layer, the second electron transport layer and the second light-emitting layer are the same. The homojunction organic electroluminescent diode has the advantages of high luminous brightness, high efficiency, high stability, wide applicable types of preparation materials and the like, and can be used as an excitation light source of an organic solid laser diode.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electroluminescence, in particular to a homojunction organic electroluminescence diode and a preparation method and application thereof. BACKGROUND

[0002] Organic solid laser diode (OSLD) is still a peak that has not been climbed in the field of organic light-emitting. At present, OSLD can be divided into indirect electric injection and direct electric injection according to current injection mode. Indirect electric injection requires an organic light-emitting diode (OLED) with super-high light-emitting efficiency as an excitation light source, but the existing OLED still needs <5ns electric pulse pumping to achieve more than 40W / cm 2 of super-high power output, which is extremely harsh to realize. Direct electric injection needs to couple an OLED device with higher efficiency than indirect electric injection into a resonant cavity with a processing precision of 5nm, and a perfect OLED device that can be coupled into the resonant cavity needs to be prepared under the harsh condition of extremely short pulse, which requires more stringent process requirements, and the produced OSLD also faces the problem of extremely poor stability, which cannot withstand more than 50 pulses under the condition of 100ns electric pulse pumping. In summary, the current driving conditions and processing methods are not suitable for promoting OSLD to large-area application fields, and the extremely poor stability also makes it difficult to produce high-good-rate products. In order to solve the above problems, the most critical thing is to improve the device efficiency and stability of OLED.

[0003] Therefore, it is of great significance to develop an organic electroluminescence diode with high efficiency and high stability. SUMMARY

[0004] The present application relates to the technical field of electroluminescence, in particular to a homojunction organic electroluminescence diode and a preparation method and application thereof.

[0005] The technical scheme adopted by the present application is:

[0006] A homojunction organic electroluminescence diode, which comprises a substrate, a bottom electrode, a first light-emitting unit, a charge generation layer, a second light-emitting unit and a top electrode which are sequentially stacked; the first light-emitting unit comprises an electron injection layer, a first electron transport layer and a first light-emitting layer which are sequentially stacked; the charge generation layer comprises a hole transport layer, a first hole injection layer, a metal layer and a second electron transport layer which are sequentially stacked; the second light-emitting unit comprises a second light-emitting layer and a second hole injection layer which are sequentially stacked; and the host materials of the first electron transport layer, the first light-emitting layer, the hole transport layer, the second electron transport layer and the second light-emitting layer are the same.

[0007] Preferably, the substrate is one of quartz substrate, aluminum oxide substrate, silicon substrate, silicon carbide substrate.

[0008] Preferably, the bottom electrode is composed of at least one of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO).

[0009] Preferably, the sheet resistance of the bottom electrode is ≤ 20 Ω / □.

[0010] Preferably, the thickness of the bottom electrode is 80 nm to 120 nm.

[0011] Preferably, the electron injection layer is composed of at least one of low work function metal, compound containing low work function metal.

[0012] Preferably, the thickness of the electron injection layer is 0.5 nm to 5 nm.

[0013] Preferably, the first electron transport layer is composed of at least one of organic light emitting material and low work function metal, compound containing low work function metal.

[0014] Preferably, the mass percentage of low work function metal or / and compound containing low work function metal in the first electron transport layer is 1% to 50%.

[0015] Preferably, the thickness of the first electron transport layer is 10 nm to 60 nm.

[0016] Preferably, the first light emitting layer is composed of organic light emitting material.

[0017] Preferably, the thickness of the first light emitting layer is 60 nm to 100 nm.

[0018] Preferably, the hole transport layer is composed of at least one of organic light emitting material and compound containing high work function metal, high hole mobility material.

[0019] Preferably, the mass percentage of compound containing high work function metal or / and high hole mobility material in the hole transport layer is 1% to 20%.

[0020] Preferably, the thickness of the hole transport layer is 10 nm to 30 nm.

[0021] Preferably, the first hole injection layer is composed of compound containing high work function metal.

[0022] Preferably, the thickness of the first hole injection layer is 1 nm to 5 nm.

[0023] Preferably, the metal layer is composed of at least one of Ag, Yb, Al.

[0024] Preferably, the thickness of the metal layer is 2-4 nm.

[0025] Preferably, the second electron transport layer is composed of at least one of an organic light-emitting material and a low work function metal or a low work function metal-containing compound.

[0026] Preferably, the mass percentage of the low work function metal or / and the low work function metal-containing compound in the second electron transport layer is 1-50%.

[0027] Preferably, the thickness of the second electron transport layer is 10-30 nm.

[0028] Preferably, the second light-emitting layer is composed of an organic light-emitting material.

[0029] Preferably, the thickness of the second light-emitting layer is 60-100 nm.

[0030] Preferably, the second hole injection layer is composed of a high work function metal-containing compound.

[0031] Preferably, the thickness of the second hole injection layer is 5-15 nm.

[0032] Preferably, the low work function metal is at least one of Yb, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce, Sm.

[0033] Preferably, the low work function metal-containing compound is at least one of 8-hydroxyquinoline-lithium, Cs2CO3, KBH4.

[0034] Preferably, the organic light-emitting material is at least one of BSBCz (4,4'-bis[(9-carbazolyl)styryl]biphenyl), TSBF (2,2":7",2"'-terphenyl-9,9'-spirobifluorene), DPAVBI (4,4'-bis[4-(di-p-tolylamino)styryl]biphenyl).

[0035] Preferably, the high work function metal-containing compound is at least one of HAT-CN (2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene), MoO x .

[0036] Preferably, the barrier between the electron injection layer, the first hole injection layer and the second hole injection layer and the first light-emitting layer and the second light-emitting layer is ≤0.2 eV (approximate ohmic contact).

[0037] Preferably, the top electrode is composed of at least one of Ag, Al and Au.

[0038] Preferably, the thickness of the top electrode is 80-120 nm.

[0039] A preparation method of the homojunction organic electroluminescent diode as described above comprises the following steps:

[0040] 1) depositing electrode material on one side of a substrate by magnetron sputtering, and then performing photolithography to form a bottom electrode;

[0041] 2) sequentially depositing a first light-emitting unit, a charge generation layer and a second light-emitting unit on the surface of the bottom electrode by evaporation, and then depositing electrode material on the surface of the second light-emitting unit by magnetron sputtering to form a top electrode, thereby obtaining the homojunction organic electroluminescent diode.

[0042] An organic solid-state laser diode, wherein the excitation light source is the homojunction organic electroluminescent diode as described above.

[0043] A display device comprising the organic solid-state laser diode as described above.

[0044] The homojunction organic electroluminescent diode of the present application has the advantages of high luminous brightness, higher efficiency under the same current density, high stability, and the like, and can be prepared using various light color carrier transport characteristic balance materials, can be used as the excitation light source of an organic solid-state laser diode, and is suitable for large-scale industrial production and application. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 Structure diagram of the homojunction organic electroluminescent diode of the embodiment.

[0046] Figure 2 Detailed structure diagram of the homojunction organic electroluminescent diode of the embodiment.

[0047] Figure 3 Detailed structure diagram of the homojunction organic electroluminescent diode of the comparative example.

[0048] Figure 4 Current density-brightness-voltage relationship curve of the homojunction organic electroluminescent diodes of the embodiment and the comparative example.

[0049] Figure 5 External quantum efficiency-current density relationship curve of the homojunction organic electroluminescent diodes of the embodiment and the comparative example.

[0050] Figure 6 Working time-driving current-luminous intensity relationship curve of the homojunction organic electroluminescent diode of the embodiment.

[0051] Figure 7 Current density-luminance-voltage curve of the homojunction organic electroluminescent diode with thin layer / thick layer charge generation layer. DETAILED DESCRIPTION

[0052] The application will be further explained and described with reference to the following specific examples.

[0053] Example:

[0054] A homojunction organic electroluminescent diode (structure diagram as shown in Figure 1 , structure diagram as shown in Figure 2 ) is composed of a substrate, a bottom electrode, a first light emitting unit, a charge generation layer, a second light emitting unit and a top electrode from bottom to top in turn; the substrate is a quartz substrate with a thickness of 500 μm; the bottom electrode is composed of ITO with a thickness of 100 nm; the first light emitting unit is composed of an electron injection layer, a first electron transport layer and a first light emitting layer from bottom to top in turn; the charge generation layer is composed of a hole transport layer, a first hole injection layer, a metal layer and a second electron transport layer from bottom to top in turn; the second light emitting unit is composed of a second light emitting layer and a second hole injection layer from bottom to top in turn; the host materials of the first electron transport layer, the first light emitting layer, the hole transport layer, the second electron transport layer and the second light emitting layer are the same; the top electrode is composed of Ag with a thickness of 100 nm.

[0055] The preparation method of the above homojunction organic electroluminescent diode is as follows:

[0056] 1) A 100 nm-thick ITO film (sheet resistance about 10 Ω / □) is deposited on one side of a quartz substrate by a magnetron sputtering method (sputtering power is 850 W, deposition time is 100 s), and then the quartz substrate is annealed at 200 ℃ for 30 min, washed with deionized water, dried in an oven at 85 ℃, spin-coated with a 1 μm-thick red photoresist RZJ-304 on the surface of the ITO film, baked on a hot plate at 100 ℃ for 90 s, exposed to laser direct writing under exposure metering of 40 mjIGH, developed in a 2.38% by mass fraction tetramethylammonium hydroxide (TMAH) solution and deionized water for 60 s each, annealed on a hot plate at 120 ℃ for 120 s, etched in a 1.0 mol / L oxalic acid solution for 150 s, and then peeled off with a 1.5 mol / L stripping agent for 10 min to form a bottom electrode;

[0057] 2) The quartz substrate treated in step 1) is washed with deionized water and dried, and then placed in a vacuum chamber with a vacuum degree less than 4×10 -4The evaporation chamber of Pa adopts evaporation method to evaporate Yb film with a thickness of 4 nm, BSBCz:Cs2CO3 film (mass ratio of BSBCz and Cs2CO3 is 2:1) with a thickness of 10 nm, BSBCz film with a thickness of 80 nm, BSBCz:MoO3 film (mass percentage of MoO3 is 20%) with a thickness of 10 nm, HAT-CN film with a thickness of 5 nm, Yb film with a thickness of 2 nm, BSBCz:Cs2CO3 film (mass percentage of MoO3 is 50%) with a thickness of 10 nm, BSBCz film with a thickness of 80 nm, MoO3 film with a thickness of 5 nm, HAT-CN film with a thickness of 8 nm and Ag film with a thickness of 100 nm on the surface of the bottom electrode in sequence, the evaporation rate is 0.1 nm / s, to form the first light-emitting unit, the charge generation layer, the second light-emitting unit and the top electrode, and then the device is placed in a glove box filled with nitrogen, packaged with a glass sheet, and a homojunction organic electroluminescent diode is obtained.

[0058] Comparative example:

[0059] A homojunction organic electroluminescent diode (the structure diagram is shown in Figure 3 The preparation method is as follows:

[0060] 1) A 100 nm-thick ITO film (sheet resistance is about 10 Ω / □) is deposited on one side of a quartz substrate by a magnetron sputtering method, the sputtering power is 850 W, the deposition time is 100 s, then the quartz substrate is annealed at 200 ℃ for 30 min, then the quartz substrate is cleaned with deionized water, then the quartz substrate is placed in an oven and dried at 85 ℃, then a 1 μm-thick red photoresist RZJ-304 is spin-coated on the surface of the ITO film, then the quartz substrate is placed on a hot plate and baked at 100 ℃ for 90 s, then the quartz substrate is exposed to laser direct writing exposure under 40 mjIGH metering, then the quartz substrate is sequentially developed in a 2.38% mass fraction tetramethylammonium hydroxide (TMAH) solution and deionized water for 60 s each, then the quartz substrate is annealed on a hot plate at 120 ℃ for 120 s, then the quartz substrate is etched in a 1.0 mol / L oxalic acid solution for 150 s, then the quartz substrate is peeled off in a 1.5 mol / L stripping agent for 10 min, and a bottom electrode is formed.

[0061] 2) The quartz substrate treated in step 1) is washed with deionized water and dried, then the quartz substrate is placed in a vacuum chamber with a vacuum degree less than 4×10 -4The evaporation chamber of Pa is used to evaporate Yb film with a thickness of 4 nm, BSBCz:Cs2CO3 film (the mass percentage of Cs2CO3 is 50%) with a thickness of 10 nm, BSBCz film with a thickness of 160 nm, MoO3 film with a thickness of 5 nm, HAT-CN film with a thickness of 8 nm and Ag film with a thickness of 100 nm on the surface of the bottom electrode in sequence, the evaporation rate is 0.1 nm / s, and then the homojunction organic electroluminescent diode is obtained by placing it in a nitrogen-filled glove box and packaging it with a glass sheet. Performance test:

[0062] The homojunction organic electroluminescent diodes of the examples and the comparative examples are driven by a pulse signal generator AVTECH / AVR-3H3-B with a pulse width of 50 ns, the luminescent brightness of the devices is collected by a photomultiplier, and the real brightness collected by a luminance meter CS2000 is corrected, and the luminescent power of the device is collected by an ophir power meter, the current density-brightness-voltage relationship curve of the device obtained by testing is shown in Figure 4 , the external quantum efficiency-current density relationship curve of the device is shown in Figure 5 (the external quantum efficiency EQE of the device is calculated by dividing the luminescent brightness by the current density), the working time-driving current-luminescent intensity relationship curve of the device is shown in Figure 6 , and the performance summary results of the device are shown in the following table:

[0063] Table 1 Performance summary results of the homojunction organic electroluminescent diodes of the examples and the comparative examples

[0064]

[0065] From Figures 4-6 and Table 1, it can be seen that:

[0066] 1) The brightness of the homojunction organic electroluminescent diode of the example can reach 3.2×10 7 cd / m 2 , which is 2.13 times that of the homojunction organic electroluminescent diode (without charge generation layer) of the comparative example;

[0067] 2) The homojunction organic electroluminescent diode of the example can last for 8 min under the electric drive of 60 V, 1kA / cm 2 , 100 Hz, and the luminescent intensity only decreases by 20%;

[0068] 3) The maximum output power density of the homojunction organic electroluminescent diode of the example reaches 42 W / cm 2 ;

[0069] In summary, the homojunction organic electroluminescent diode of the embodiment has the advantages of high efficiency and high stability, and can be used as an excitation light source for an organic solid-state laser diode (indirect electrical injection).

[0070] The thickness of the BSBCz:Cs2CO3 film in the embodiment was adjusted from "10nm" to "30nm" and the thickness of the BSBCz:MoO3 film was adjusted from "10nm" to "30nm" to obtain a homojunction organic electroluminescent diode with a thick charge generation layer (denoted as "thick layer"). The device was then subjected to performance testing (testing method is the same as above). The current density-brightness-voltage relationship curve obtained by the test is shown as follows: Figure 7 (The homojunction organic electroluminescent diode of the embodiment is used as a comparison, which has a thin charge generation layer, denoted as "thin layer").

[0071] Depend on Figure 7 It can be seen that the homojunction organic electroluminescent diode with a thin charge generation layer (Example) has higher brightness than the homojunction organic electroluminescent diode with a thick charge generation layer, which indicates that the charge generation ability of the thin charge generation layer is stronger than that of the thick charge generation layer.

[0072] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A homojunction organic light-emitting diode, characterized in that: The composition includes a substrate, a bottom electrode, a first light-emitting unit, a charge generation layer, a second light-emitting unit and a top electrode stacked in sequence; the composition of the first light-emitting unit includes an electron injection layer, a first electron transport layer and a first light-emitting layer stacked in sequence; the composition of the charge generation layer includes a hole transport layer, a first hole injection layer, a metal layer and a second electron transport layer stacked in sequence; the composition of the second light-emitting unit includes a second light-emitting layer and a second hole injection layer stacked in sequence; the main materials of the first electron transport layer, the first light-emitting layer, the hole transport layer, the second electron transport layer and the second light-emitting layer are the same; the main material is 4,4'-bis[(9-carbazolyl)phenylvinyl]biphenyl.

2. The homojunction organic light-emitting diode according to claim 1, wherein: The electron injection layer is composed of at least one of a low work function metal and a compound containing a low work function metal; the first electron transport layer is composed of an organic light-emitting material and at least one of a low work function metal and a compound containing a low work function metal; the first light-emitting layer is composed of an organic light-emitting material; the low work function metal is at least one of Yb, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce, and Sm; the compound containing a low work function metal is at least one of 8-hydroxyquinoline-lithium, Cs2CO3, and KBH4; the organic light-emitting material is at least one of BSBCz, TSBF, and DPAVBI.

3. The homojunction organic light-emitting diode according to claim 1, wherein: The hole transport layer is composed of an organic light-emitting material and a compound containing a high work function metal, or a high hole mobility material; the first hole injection layer is composed of a compound containing a high work function metal; the metal layer is composed of at least one of Ag, Yb, and Al; the second electron transport layer is composed of an organic light-emitting material and a low work function metal, or a compound containing a low work function metal; the organic light-emitting material is at least one of BSBCz, TSBF, and DPAVBI; the compound containing a high work function metal is at least one of HAT-CN and MoOx; the low work function metal is at least one of Yb, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce, and Sm; the compound containing a low work function metal is at least one of 8-hydroxyquinoline-lithium, Cs2CO3, and KBH4.

4. The homojunction organic light-emitting diode according to claim 1, wherein: The second light-emitting layer is composed of an organic light-emitting material; the organic light-emitting material is at least one of BSBCz, TSBF, and DPAVBI; the second hole injection layer is composed of a compound containing a high work function metal; the compound containing a high work function metal is HAT-CN, MoO x At least one of .

5. The homojunction organic light-emitting diode according to any one of claims 1 to 4, characterized in that: The thickness of the electron injection layer is 0.5nm to 5nm; the thickness of the first electron transport layer is 10nm to 60nm; the thickness of the first light-emitting layer is 60nm to 100nm; the thickness of the hole transport layer is 10nm to 30nm; the thickness of the first hole injection layer is 1nm to 5nm; the thickness of the metal layer is 2nm to 4nm; the thickness of the second electron transport layer is 10nm to 30nm; the thickness of the second light-emitting layer is 60nm to 100nm; and the thickness of the second hole injection layer is 5nm to 15nm.

6. The homojunction organic light-emitting diode according to any one of claims 1 to 4, characterized in that: The substrate is one of a quartz substrate, an aluminum oxide substrate, a silicon substrate, and a silicon carbide substrate; the component of the bottom electrode is at least one of indium tin oxide, indium zinc oxide, and zinc oxide; and the component of the top electrode is at least one of Ag, Al, and Au.

7. The homojunction organic light-emitting diode according to any one of claims 1 to 4, characterized in that: The thickness of the bottom electrode is 80nm to 120nm; the thickness of the top electrode is 80nm to 120nm.

8. A method for preparing a homojunction organic light-emitting diode according to any one of claims 1 to 7, characterized in that: The following steps are involved: 1) Electrode material is deposited on one side of the substrate using magnetron sputtering, followed by photolithography to form a bottom electrode; 2) The first light-emitting unit, the charge generation layer, and the second light-emitting unit are sequentially deposited on the surface of the bottom electrode by an evaporation method, and then the electrode material is deposited on the surface of the second light-emitting unit by a magnetron sputtering method to form a top electrode, thereby obtaining a homojunction organic electroluminescent diode.

9. An organic solid-state laser diode, characterized in that: The excitation light source is the homojunction organic electroluminescent diode according to any one of claims 1 to 7.

10. A display device, characterized in that: The organic solid-state laser diode according to claim 9 is included.

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