Homojunction organic light-emitting diode and preparation method and application thereof

Abstract

The invention discloses a homojunction organic light-emitting diode and a preparation method and application thereof. The homojunction organic light-emitting 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 stacked, and the first light-emitting unit comprises an electron injection layer, a first electron transport layer and a first light-emitting layer. The charge generation layer comprises a hole transport layer, a first hole injection layer, a metal layer and a second electron transport layer, the second light-emitting unit comprises a second light-emitting layer and a second hole injection layer, and the main body 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 light-emitting diode disclosed by the invention has the advantages of high luminance, high efficiency, high stability, wide applicable preparation material types and the like, and can be used as an excitation light source of an organic solid laser diode.

Description

Technical Field

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

[0002] Organic solid laser diode (OSLD) is still the peak that has not yet been climbed in the field of organic light-emitting. At present, OSLD can be divided into two types according to the current injection method: indirect electric injection and direct electric injection. Indirect electric injection requires an organic light-emitting diode (OLED) with ultra-high luminous efficiency as the excitation light source, but the existing OLED wants to achieve more than 40W / cm 2 Ultra-high power output still requires electric pulse pumping of <5ns, and the conditions for achieving it are extremely harsh. Direct electric injection requires coupling OLED devices with higher efficiency than indirect electric injection into a resonant cavity with a processing accuracy of 5nm. Under the harsh conditions of extremely short pulses, it is even more necessary to prepare perfect OLED devices that can be coupled into the resonant cavity. The process requirements are more stringent, and the produced OSLD will also face the problem of extremely poor stability. It cannot last more than 50 pulses under electric pulse pumping of hundreds of ns. In summary, the current harsh driving conditions and processing methods are not suitable for promoting OSLD to large-scale applications, and the extremely poor stability also makes it difficult to prepare products with high yields. In order to solve the above problems, the most critical thing is to improve the efficiency and stability of OLED devices.

[0003] Therefore, it is of great significance to develop an organic light-emitting diode with high efficiency and high stability. Summary of the invention

[0004] The object of the present invention is to provide a homojunction organic electroluminescent diode and a preparation method and application thereof.

[0005] The technical solution adopted by the present invention is:

[0006] A homojunction organic electroluminescent diode, comprising 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 first light-emitting unit comprises an electron injection layer, a first electron transport layer and a first light-emitting layer stacked in sequence; the charge generation layer comprises a hole transport layer, a first hole injection layer, a metal layer and a second electron transport layer stacked in sequence; the second light-emitting unit comprises 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.

[0007] Preferably, the substrate is one of a quartz substrate, an alumina substrate, a silicon substrate, and a silicon carbide substrate.

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

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

[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 a low work function metal and a compound containing a low work function metal.

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

[0013] Preferably, 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.

[0014] Preferably, the mass percentage of the low work function metal or / and the compound containing the 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 an 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 an organic light-emitting material and a compound containing a high work function metal and a high hole mobility material.

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

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

[0021] Preferably, the first hole injection layer is composed of a compound containing a 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 and Al.

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

[0025] Preferably, the second 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.

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

[0027] Preferably, the second electron transport layer has a thickness of 10 nm to 30 nm.

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

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

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

[0031] Preferably, the second hole injection layer has a thickness of 5 nm to 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, and Sm.

[0033] Preferably, the compound containing a low work function metal is 8-hydroxyquinoline-lithium, Cs 2 CO 3 KBH 4 At least one of .

[0034] Preferably, the organic light-emitting material is at least one of BSBCz (4,4'-bis[(9-carbazolyl)phenylvinyl]biphenyl), TSBF (2,2":7",2"'-tert-9,9'-spirobis[9H-fluorene]), and DPAVBI (4,4'-bis[4-(di-p-tolylamino)phenylvinyl]biphenyl).

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

[0036] Preferably, the potential barriers 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 are ≤0.2 eV (approximately 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 nm to 120 nm.

[0039] A method for preparing the homojunction organic light-emitting diode as described above comprises the following steps:

[0040] 1) Electrode material is deposited on one side of the substrate by magnetron sputtering, and then photolithography is performed to form a bottom electrode;

[0041] 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 evaporation, and then the electrode material is deposited on the surface of the second light-emitting unit by magnetron sputtering to form a top electrode, thereby obtaining a homojunction organic light-emitting diode.

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

[0043] A display device comprises the organic solid laser diode.

[0044] The beneficial effects of the present invention are as follows: the homojunction organic electroluminescent diode of the present invention has the advantages of high luminous brightness, higher efficiency at the same current density, high stability, and can be prepared using materials with balanced carrier transport characteristics of various light colors. It can be used as an excitation light source for organic solid-state laser diodes and is suitable for large-scale industrial production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 FIG. 4 is a simplified structural diagram of a homojunction organic light emitting diode according to an embodiment.

[0046] Figure 2 Detailed structural diagram of a homojunction organic light emitting diode according to an embodiment.

[0047] Figure 3 Detailed structural diagram of a homojunction organic light emitting diode of a comparative example.

[0048] Figure 4 The current density-brightness-voltage relationship curves of the homojunction organic light emitting diodes of the embodiment and the comparative example are shown.

[0049] Figure 5 The graphs are the relationship between external quantum efficiency and current density of the homojunction organic light emitting diodes of the embodiment and the comparative example.

[0050] Figure 6 The graph is a working time-driving current-luminous intensity relationship curve of the homojunction organic light emitting diode of the embodiment.

[0051] Figure 7 The current density-brightness-voltage relationship curve of a homojunction organic light-emitting diode with a thin / thick charge generation layer. DETAILED DESCRIPTION

[0052] The present invention will be further explained and illustrated below in conjunction with specific embodiments.

[0053] Example:

[0054] A homojunction organic light emitting diode (structure diagram as shown in Figure 1 The structural details are shown in Figure 2 As shown), it 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 stacked in sequence from bottom to top; the substrate is a quartz substrate with a thickness of 500μm; the bottom electrode is composed of ITO with a thickness of 100nm; the first light-emitting unit is composed of an electron injection layer, a first electron transport layer and a first light-emitting layer stacked in sequence from bottom to top; 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 stacked in sequence from bottom to top; the second light-emitting unit is composed of a second light-emitting layer and a second hole injection layer stacked in sequence from bottom to top; 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 top electrode is composed of Ag with a thickness of 100nm.

[0055] The preparation method of the homojunction organic light-emitting diode is as follows:

[0056] 1) A 100 nm thick ITO film (square resistance of about 10Ω / □) was deposited on a single side of a quartz substrate by magnetron sputtering, with a sputtering power of 850 W and a deposition time of 100 s, followed by annealing at 200° C. for 30 min, washing with deionized water and drying in an oven at 85° C., then spin-coating a 1 μm thick Ruihong RZJ-304 photoresist on the surface of the ITO film, then baking at 100° C. for 90 s on a hot plate, then performing laser direct writing exposure at 40 mjIGH exposure metering, then developing in a 2.38% mass fraction tetramethylammonium hydroxide (TMAH) solution and deionized water for 60 s each, then annealing at 120° C. for 120 s on a hot plate, then etching in a 1.0 mol / L oxalic acid solution for 150 s, and then removing the glue for 10 min using a stripping solution with a concentration of 1.5 mol / L to form a bottom electrode;

[0057] 2) The quartz substrate treated in step 1) was washed with deionized water and dried, and then placed in a vacuum chamber with a degree of <4×10 -4 Pa's evaporation chamber uses evaporation to deposit a 4nm thick Yb film, a 10nm thick BSBCz:Cs 2 CO 3 Thin films (BSBCz, Cs 2 CO 3 The mass ratio of BSBCz:MoO is 2:1), BSBCz film with a thickness of 80nm, and BSBCz:MoO with a thickness of 10nm. 3 Thin film (MoO 3 The mass percentage is 20%), a HAT-CN film with a thickness of 5nm, a Yb film with a thickness of 2nm, and a BSBCz:Cs film with a thickness of 10nm. 2 CO 3 Thin film (MoO 3 The mass percentage is 50%), BSBCz film with a thickness of 80nm, MoO with a thickness of 5nm 3 A thin film, a HAT-CN film with a thickness of 8 nm and a Ag film with a thickness of 100 nm were deposited at a rate of 0.1 nm / s to form a first light-emitting unit, a charge generation layer, a second light-emitting unit and a top electrode, which were then placed in a nitrogen-filled glove box and encapsulated using a glass sheet to obtain a homojunction organic electroluminescent diode.

[0058] Comparative Example:

[0059] A homojunction organic light emitting diode (structural details as shown in FIG. Figure 3 The preparation method thereof is as follows:

[0060] 1) A 100 nm thick ITO film (square resistance of about 10Ω / □) was deposited on a single side of a quartz substrate by magnetron sputtering, with a sputtering power of 850 W and a deposition time of 100 s, followed by annealing at 200° C. for 30 min, washing with deionized water and drying in an oven at 85° C., then spin-coating a 1 μm thick Ruihong RZJ-304 photoresist on the surface of the ITO film, then baking at 100° C. for 90 s on a hot plate, then performing laser direct writing exposure at 40 mjIGH exposure metering, then developing in a 2.38% mass fraction tetramethylammonium hydroxide (TMAH) solution and deionized water for 60 s each, then annealing at 120° C. for 120 s on a hot plate, then etching in a 1.0 mol / L oxalic acid solution for 150 s, and then removing the glue for 10 min using a stripping solution with a concentration of 1.5 mol / L to form a bottom electrode;

[0061] 2) The quartz substrate treated in step 1) was washed with deionized water and dried, and then placed in a vacuum chamber with a degree of <4×10 -4Pa's evaporation chamber uses evaporation to deposit a 4nm thick Yb film, a 10nm thick BSBCz:Cs 2 CO 3 Film (Cs 2 CO 3 The mass percentage of the BSBCz film is 50%), the thickness of the BSBCz film is 160nm, the thickness of the MoO 3 Thin film, 8nm thick HAT-CN thin film and 100nm thick Ag thin film, the evaporation rate is 0.1nm / s, and then placed in a nitrogen-filled glove box and encapsulated with a glass sheet to obtain a homojunction organic electroluminescent diode. Performance test:

[0062] The pulse signal generator AVTECH / AVR-3H3-B is used to pass an electric pulse with a pulse width of 50ns on the homojunction organic light-emitting diodes of the embodiment and the comparative example, and then the luminous brightness of the device is collected by a photomultiplier tube and corrected with the real brightness collected by a brightness meter CS2000, and the luminous power of the device is collected by an ophir power meter. The current density-brightness-voltage relationship curve of the device obtained by the test is as follows Figure 4 As shown, the device's external quantum efficiency-current density relationship curve is as follows Figure 5 As shown (the external quantum efficiency EQE of the device is calculated by dividing the luminous brightness by the current density), the working time-driving current-luminous intensity relationship curve of the device is as follows Figure 6 The performance summary results of the device are shown in the following table:

[0063] Table 1 Summary of performance results of homojunction organic light emitting diodes of embodiments and comparative examples

[0064]

[0065] Depend on Figures 4 to 6 From Table 1, we can see that:

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

[0067] 2) The homojunction organic light emitting diode of the embodiment is subjected to 60V and 1kA / cm 2 , it can last for 8 minutes under 100Hz electric drive, and the luminous intensity only decreases by 20%;

[0068] 3) The maximum output power density of the homojunction organic light-emitting diode of the embodiment reaches 42W / cm 2 ;

[0069] In summary, the homojunction organic light-emitting 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 BSBCz:Cs 2 CO 3 The thickness of the film was adjusted from "10nm" to "30nm" and BSBCz:MoO 3 The thickness of the film was adjusted from "10nm" to "30nm", and a homojunction organic electroluminescent diode with a thick charge generation layer (referred to as "thick layer") was obtained. The device was then tested for performance (the test method is the same as above). The current density-brightness-voltage relationship curve obtained by the test is shown in FIG. 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 light-emitting diode with a thin charge generation layer (example) has higher brightness than the homojunction organic light-emitting diode with a thick charge generation layer, indicating 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 equivalent replacement methods and are included in the protection scope 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 which are 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 which are 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 which are stacked in sequence; the composition of the second light-emitting unit includes a second light-emitting layer and a second hole injection layer which are 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.

2. The homojunction organic light emitting diode according to claim 1, characterized in that: 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, characterized in that: The hole transport layer is composed of an organic light-emitting material and a compound containing a high work function metal, and at least one of 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, and at least one of 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, characterized in that: 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~5nm; the thickness of the first electron transport layer is 10nm~60nm; the thickness of the first light-emitting layer is 60nm~100nm; the thickness of the hole transport layer is 10nm~30nm; the thickness of the first hole injection layer is 1nm~5nm; the thickness of the metal layer is 2nm~4nm; the thickness of the second electron transport layer is 10nm~30nm; the thickness of the second light-emitting layer is 60nm~100nm; the thickness of the second hole injection layer is 5nm~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; 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-120nm; the thickness of the top electrode is 80nm-120nm.

8. A method for preparing a homojunction organic light-emitting diode as claimed in 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 by magnetron sputtering, and then photolithography is performed 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 evaporation, and then the electrode material is deposited on the surface of the second light-emitting unit by magnetron sputtering to form a top electrode, thereby obtaining a homojunction organic light-emitting diode.

9. An organic solid laser diode, characterized in that: The excitation light source is the homojunction organic light emitting diode as claimed in any one of claims 1 to 7.

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

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