CN108269931B - Organic electroluminescent device and preparation method thereof - Google Patents
Organic electroluminescent device and preparation method thereof Download PDFInfo
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- CN108269931B CN108269931B CN201611257711.2A CN201611257711A CN108269931B CN 108269931 B CN108269931 B CN 108269931B CN 201611257711 A CN201611257711 A CN 201611257711A CN 108269931 B CN108269931 B CN 108269931B
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- H10K50/00—Organic light-emitting devices
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- H10K50/171—Electron injection layers
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- H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
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Abstract
In order to solve the problem that the quenching probability of the luminescent center of the organic electroluminescent device in the prior art is high, the embodiment of the application provides an organic electroluminescent device and a preparation method thereof. An organic electroluminescent device comprises an electron injection layer, wherein the electron injection layer comprises at least one coordination compound formed from at least one inert metal simple substance and at least one electron transport material, wherein the at least one electron transport material has coordination capability and comprises an N ^ O and/or N ^ N heterocyclic ring.
Description
Technical Field
The application relates to the field of organic electroluminescent devices, in particular to an organic electroluminescent device and a preparation method thereof.
Background
With the development of science and technology, the application range of organic electroluminescent devices is wider and wider.
Among them, the recombination rate (γ) of electrons and holes is an important factor affecting the light emitting efficiency of the organic electroluminescent device. Therefore, it is an optimum means to improve the quantum efficiency by making the gamma value close to 1.0 by making the injection of electrons and holes more balanced. However, in the existing organic electroluminescent device, the number of holes in the light emitting layer is two orders of magnitude larger than that of electrons in the light emitting layer, which results in that the light emitting layer of the organic electroluminescent device has a lower recombination rate of holes and electrons, and therefore, reducing the number of holes or improving the electron injection capability is a solution for improving the light emitting efficiency of the device. An organic electroluminescent device generally includes a substrate, an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a cathode.
The electron injection layer is used for promoting injection of free electrons from the cathode to the electron transport layer, reducing driving voltage and saving resources. In the prior art, the material of the electron injection layer of the organic electroluminescent device is generally an alkali metal compound, such as lithium oxide, lithium boron oxide, potassium carbonate, cesium carbonate, and the like. The organic electroluminescent device made of the alkali metal compound can effectively reduce the driving voltage and improve the current efficiency of the device. Another commonly used material of the electron injection layer is alkali metal fluoride, such as lithium fluoride LiF, and especially the characteristics that the LiF/Al structure has ohmic contact reduce the injection barrier of electrons, improve the efficiency of the device and reduce the driving voltage of the device.
However, alkali metals are relatively active, which is not favorable for long-time storage, and flocculent dust is easily generated in the vacuum evaporation process, which seriously affects the production efficiency and the product yield. In addition, the metal ions are likely to migrate to the light-emitting layer, which tends to cause quenching of the light-emitting center of the organic electroluminescent device.
Disclosure of Invention
The embodiment of the application provides an organic electroluminescent device and a preparation method and device thereof, which are used for solving the problem that the probability of quenching of a luminescent center of the organic electroluminescent device in the prior art is high.
The embodiment of the application adopts the following technical scheme:
an organic electroluminescent device comprising an electron injection layer comprising at least one coordination compound formed from at least one inert metal simple substance and at least one electron transport material, wherein the at least one electron transport material has coordination capability and comprises N ^ O and/or N ^ N heterocycles.
A method of manufacturing an organic electroluminescent device comprising a substrate, an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, a cathode, the method comprising:
the anode, the hole transport layer, the light emitting layer, the electron transport layer, the electron injection layer, and the cathode, which are stacked on each other, are sequentially vapor-deposited on the substrate,
when the electron injection layer is evaporated, at least one inert metal simple substance and at least one electron transport material are evaporated by adopting a hybrid evaporation method, so that at least one inert metal simple substance and at least one electron transport material form at least one coordination compound in the evaporation process, wherein the at least one electron transport material has coordination capacity and contains N ^ O and/or N ^ N heterocyclic rings.
The embodiment of the application adopts at least one technical scheme which can achieve the following beneficial effects:
the electron injection layer in the organic electroluminescent device provided by the embodiment of the application comprises a coordination compound formed by at least one inert metal simple substance and at least one electron transport material. Wherein the at least one electron transport material has coordination capability and comprises N ^ O and/or N ^ N heterocycles.
The complex included in the electron injection layer has a low work function and is matched with the LUMO level of the electron transport layer, so that an injection barrier of free electrons can be reduced, and the inhibition of injection of free electrons from the cathode into the electron transport layer can be reduced, thereby facilitating injection of free electrons from the cathode into the electron transport layer and reducing the driving voltage. In addition, the coordination compound included in the electron injection layer has stable property, and the complexing action between the inert metal ions and the electron transport material is large, so that the metal ions are not easy to migrate to the light-emitting layer, thereby solving the problem that the probability of quenching the light-emitting center of the organic electroluminescent device in the prior art is high.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:
fig. 1 is a schematic structural diagram of an organic electroluminescent device provided in an embodiment of the present application;
FIG. 2 is a graph of voltage versus current density provided by an embodiment of the present application;
fig. 3 is a graph illustrating the relationship between luminance and current efficiency according to an embodiment of the present disclosure.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail and completely with reference to the following specific embodiments of the present application and the accompanying drawings. It should be apparent that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The technical solutions provided by the embodiments of the present application are described in detail below with reference to the accompanying drawings.
In order to solve the problem that the probability of quenching the luminescence center of the organic electroluminescent device in the prior art is high, the embodiment of the application provides an organic electroluminescent device. The organic electroluminescent device may be a top emission organic electronic light emitting device or a bottom emission organic electroluminescent device, which is not limited in this embodiment.
A specific structural schematic diagram of an organic electroluminescent device 100 provided in an embodiment of the present application is shown in fig. 1. The organic electroluminescent device 100 may include a substrate 101, an anode 102, a hole injection layer 103, a hole transport layer 104, a light emitting layer 105, an electron transport layer 106, an electron injection layer 107, a cathode 108, a wire 109 connected to the anode 102, and a wire 110 connected to the cathode 108.
The above-mentioned electron injection layer 107 may include at least one coordination compound formed of at least one inert metal simple substance and at least one electron transport material, wherein the at least one electron transport material has a coordination ability and contains an N ^ O and/or an N ^ N heterocyclic ring.
The at least one inert elemental metal may include, but is not limited to, at least one of titanium Ti, vanadium V, chromium Cr, manganese Mn, iron Fe, cobalt Co, nickel Ni, copper Cu, zinc Zn, zirconium Zr, niobium Nb, molybdenum Mo, technetium Tc, ruthenium Ru, rhodium Rh, lead Pb, silver Ag, cadmium Cd, tantalum Ta, tungsten W, rhenium Re, osmium Os, iridium Ir, gold Au, platinum Pt, or mercury Hg. The inert metal simple substance is stable in air, and the work function is higher than 4.0V. One of the at least one kind of simple inert metal may be the same as or different from the cathode 108, and this is not limited in this embodiment.
Preferably, the at least one inert elemental metal may include, but is not limited to, at least one of cobalt Co, nickel Ni, copper Cu, ruthenium Ru, silver Ag, iridium Ir, gold Au, or platinum Pt. The inert metal simple substances have stronger coordination capability, and can more easily form a coordination compound with an electron transport material, so that the finally formed coordination compound is more stable.
The at least one electron transport host material corresponding to the at least one electron transport material may be selected from at least one of materials having structural formulae (1) to (12):
wherein R is1、R2、R3、R4、R5、R6、R7、R8Selected from hydrogen radical, alkyl (-C)nH2n+1) Conjugated aromatic group, conjugated heterocyclic ring, methoxy (-OCH)3) Amino and alkyl substituted amino (-NR)xH2-x) Cyano (-CN) and cyanoalkyl chain (-C)nH2n-CN), halogen (-X) and haloalkyl (-haloalkyl), aldehyde (-OR), and keto (-CHO, -COR)2) And a formylalkyl chain (-C)nH2n-CHO), ester group (-COOR) and ester alkyl chain (-C)nH2n-COOR), or acetylacetonate (-COCH)2COR) and acetylacetonyl alkyl chain (-C)nH2n-COCH2COR), the conjugated aromatic group is phenyl (-Ph), naphthyl or anthryl, and the conjugated heterocyclic ring is pyridyl (-Py) or quinolyl.
The above-mentioned at least one electron transport material may be one selected from materials having structural formulae such as (2-1) to (9-1):
the volume ratio of the inert metal simple substance to the electron transport material can be 1: 99-99: 1, or the mass ratio of the inert metal simple substance to the electron transport material can be 1: 99-99: 1.
Preferably, the mass ratio of the inert metal simple substance to the electron transport material can be 5: 95-30: 70.
For example, if the inert metal simple substance is silver and the electron transport material is an electron transport material having a structural formula (5-1), i.e. 4, 7-diphenyl-1, 10-phenanthroline, the structural formula of the coordination compound formed by silver and 4, 7-diphenyl-1, 10-phenanthroline may be:
or (b).
The materials of the substrate 101, the anode 102, the hole injection layer 103, the hole transport layer 104, the light emitting layer 105, the electron transport layer 106, the cathode 108, the wire 109 and the wire 110 in the organic electroluminescent device 100 may be materials of a substrate, an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, a cathode, a wire connected to the anode and a wire connected to the cathode, which are often applied in organic electroluminescent devices in the prior art, and are not described herein again.
In the embodiment of the present application, the work function of the coordination compound included in the electron injection layer 107 is low, and the work function is matched with the LUMO level of the electron transport layer 106, so that the injection barrier of free electrons can be reduced, and the inhibition of injection of free electrons from the cathode 108 into the electron transport layer 106 can be reduced, thereby facilitating injection of free electrons from the cathode 108 into the electron transport layer 106, and reducing the driving voltage. In addition, the at least one inert metal and the at least one electron transport material are each electrically neutral, and when the at least one inert metal and the at least one electron transport material are deposited on the electron transport layer 106 by a hybrid deposition method, the at least one inert metal loses electrons and eventually forms a complex compound having an electropositive property with the at least one electron transport material. Then free electrons are present in the electron injection layer 107. This increases the number of free electrons injected into the electron transport layer 106, thereby increasing the electron injection efficiency. Therefore, the complex compound can be used as a material constituting the electron injection layer and can function as an electron injection layer. The coordination compound included in the electron injection layer has stable property, and the inert metal ions and the electron transport material have large complexation, so that the metal ions are not easy to migrate to the light-emitting layer, thereby reducing the probability of quenching the light-emitting center of the organic electroluminescent device in the prior art.
It should be noted that, when the organic electroluminescent device provided in the embodiment of the present application is a top-emission organic electroluminescent device, the top-emission organic electroluminescent device can reduce the probability of quenching of the luminescent center of the organic electroluminescent device in the prior art, and can also solve the problem that the light transmittance of the top-emission organic electroluminescent device in the prior art is gradually reduced in the use process. Specifically, in the prior art, the electron injection layer of some top emission organic electroluminescent devices is made of an active metal simple substance, but the active metal is easily oxidized to form an oxide, wherein the transmittance of the oxide is low, the longer the service time of the top emission organic electroluminescent devices is, the higher the oxidation degree of the active metal is, the more the oxide is formed, and thus the transmittance of the top emission organic electroluminescent devices is lower and lower in the use process. The material of the electron injection layer of the top-emitting organic electroluminescent device provided in the embodiment of the present application may be at least one coordination compound formed by at least one inert metal simple substance and at least one electron transport material, and the electron injection layer does not include an active metal, and therefore, the electron injection layer is not oxidized to form an oxide in the use process, so that the light transmittance of the top-emitting organic electroluminescent device is not gradually reduced in the use process, and therefore, the problem that the light transmittance of the top-emitting organic electroluminescent device in the prior art is gradually reduced in the use process can be solved.
Example 1
Example 1 may take a top-emission organic electroluminescent device as an example, where the top-emission organic electroluminescent device may use Ag as a reflective metal layer material, Indium Tin Oxide (ITO) as an anode material, 4, 4, 4-tris (carbazol-9-yl) triphenylamine (TCTA) as a hole injection layer material, N ' -diphenyl-N, N ' - (1-naphthyl) -1, 1' -biphenyl-4, 4' -diamine (NPB) as a hole transport layer material, and 4, 4' -bis (9-Carbazol) Biphenyl (CBP) as a light emitting layer material, where ir is (ppy)3The mass percentage of the doped material in the light emitting layer is 15%, 4, 7-diphenyl-1, 10-phenanthroline (Bphen) is used as an electron transport layer material, a coordination compound formed by a substance with a chemical structural formula of formula (4-1) and Ag in the embodiment of the application is used as an electron injection layer material, wherein the mass percentage of the doped material of Ag in the chemical structural formula of formula (4-1) is 5%, and Ag is used as a semitransparent cathode material. In addition, the thickness of the reflective metal layer of the top-emission organic electroluminescent device is 10nm, the thickness of the transparent anode is 15nm, the thickness of the hole injection layer is 10nm, the thickness of the hole transport layer is 10nm, the thickness of the light-emitting layer is 30 nm, the thickness of the electron transport layer is 20nm, and the thickness of the electron injection layer is 10nm and the thickness of the semitransparent cathode is 10 nm. Example 1 a top emission organic electroluminescent device structure is as follows:
Ag(10nm)/ITO(15nm)/HATCN(10nm)/NPB(30nm)/CBP:15wt％Ir(ppy)3/Bphen (20 nm)/formula (4-1): 5% Ag (10nm)/Ag (10nm)
Example 2
The structure of the top-emission organic electroluminescent device provided in example 2 is as follows:
Ag(10nm)/ITO(15nm)/HATCN(10nm)/NPB(30nm)/CBP:15wt％Ir(ppy)3/Bphen (20 nm)/formula (4-1): 10% Ag (10nm)/Ag (10nm)
Example 3
The structure of the top-emission organic electroluminescent device provided in example 3 is as follows:
Ag(10nm)/ITO(15nm)/HATCN(10nm)/NPB(30nm)/CBP:15wt％Ir(ppy)3/Bphen (20 nm)/formula (4-1): 25% Ag (10nm)/Ag (10nm)
Comparative example 1
The structure of the top-emission organic electroluminescent device provided in comparative example 1 is as follows:
Ag(10nm)/ITO(15nm)/HATCN(10nm)/NPB(30nm)/CBP:15wt％Ir(ppy)3/Bphen(30nm)/Ag(10nm)
comparative example 2
The structure of the top-emission organic electroluminescent device provided in comparative example 2 is as follows:
Ag(10nm)/ITO(15nm)/HATCN(10nm)/NPB(30nm)/CBP:15wt％Ir(ppy)3/Bphen(20nm)/Mg(2nm)：Ag(8nm)/Ag(10nm)
it should be noted that the thicknesses of the top-emitting organic electroluminescent devices provided in the above examples 1, 2, 3, 1 and 2 are the same.
Watch 1
As shown in table one, comparative example 1 does not use an electron injection layer, has a very large injection barrier between the cathode and the electron transport layer, and electrons are hardly injected into the device, resulting in very high driving voltage of comparative example 1; in examples 1 to 3, the electron transport material having the structural formula (4-1) is mixed with an inert metal Ag with different concentrations for evaporation, wherein when the mass fraction of Ag is 10%, the top-emitting organic electroluminescent device has the best performance. Wherein, the lower the driving voltage, the higher the electron injection efficiency, which indicates the better performance of the top emission organic electroluminescent device. The performance of example 2 is superior to that of comparative example 2 in both driving voltage and efficiency, which shows that the work function of the complex compound formed by the electron transport material having the structural formula (4-1) and the inert metal Ag is low, and the injection barrier of free electrons can be lowered, and the barrier for injecting free electrons from the cathode into the electron transport layer can be reduced, so that the injection of free electrons from the cathode into the electron transport layer can be promoted, and the driving voltage can be lowered. In addition, as can be seen from the voltage-current density relationship diagram shown in fig. 2 and the luminance-current efficiency relationship diagram shown in fig. 3, the top-emission organic electroluminescent device provided in example 2 has the best performance. In fig. 2 and 3, Ag is used to represent a top emission organic electroluminescent device in which the material of the electron injection layer is Ag, and Mg: ag is used to represent a top emission organic electroluminescent device in which the material of the electron injection layer is a magnesium-silver alloy, the top emission organic electroluminescent device of fig. 2 and 3 in which 5% is used to represent the material of the electron injection layer is a complex of 5% by mass of Ag and 95% by mass of the electron input material corresponding to formula (4-1), 10% in FIGS. 2 and 3 is a top-emission organic electroluminescent device in which the material for the electron injection layer is a complex of 10% by mass of Ag and 90% by mass of an electron input material corresponding to formula (4-1), the top emission organic electroluminescent device of fig. 2 and 3 in which 10% is used to represent the material of the electron injection layer is a complex of 25% by mass of Ag and 75% by mass of the electron input material corresponding to formula (4-1).
Example 4
The structure of the top-emission organic electroluminescent device provided in example 4 is as follows:
Ag(10nm)/ITO(15nm)/HATCN(10nm)/NPB(30nm)/CBP:15wt％Ir(ppy)3/Bphen (20 nm)/formula (2-3): 10% Ag (10nm)/Ag (10nm)
Example 5
The structure of the top-emission organic electroluminescent device provided in example 5 is as follows:
Ag(10nm)/ITO(15nm)/HATCN(10nm)/NPB(30nm)/CBP:15wt％Ir(ppy)3/Bphen (20 nm)/formula (3-1): 10% Ir (10nm)/Ag (10nm)
Example 6
The structure of the top-emission organic electroluminescent device provided in example 6 is as follows:
Ag(10nm)/ITO(15nm)/HATCN(10nm)/NPB(30nm)/CBP:15wt％Ir(ppy)3/Bphen (20 nm)/formula (4-3): 10% Co (10nm)/Ag (10nm)
Example 7
The structure of the top-emission organic electroluminescent device provided in example 7 is as follows:
Ag(10nm)/ITO(15nm)/HATCN(10nm)/NPB(30nm)/CBP:15wt％Ir(ppy)3/Bphen (20 nm)/formula (4-10): 10% Pt (10nm)/Ag (10nm)
Example 8
The structure of the top-emission organic electroluminescent device provided in example 8 is as follows:
Ag(10nm)/ITO(15nm)/HATCN(10nm)/NPB(30nm)/CBP:15wt％Ir(ppy)3/Bphen (20 nm)/formula (5-6): 10% Ru (10nm)/Ag (10nm)
Example 9
The structure of the top-emission organic electroluminescent device provided in example 9 is as follows:
Ag(10nm)/ITO(15nm)/HATCN(10nm)/NPB(30nm)/CBP:15wt％Ir(ppy)3/Bphen (20 nm)/formula (5-10): 10% Ni (10nm)/Ag (10nm)
Example 10
The structure of the top-emission organic electroluminescent device provided in example 10 is as follows:
Ag(10nm)/ITO(15nm)/HATCN(10nm)/NPB(30nm)/CBP:15wt％Ir(ppy)3/Bphen (20 nm)/formula (5-17): 10 percent ofAu(10nm)/Ag(10nm)
Example 11
Example 11 provides a top-emission organic electroluminescent device having the following structure:
Ag(10nm)/ITO(15nm)/HATCN(10nm)/NPB(30nm)/CBP:15wt％Ir(ppy)3/Bphen (20 nm)/formula (6-2): 10% Cu (10nm)/Ag (10nm)
Example 12
The structure of the top-emission organic electroluminescent device provided in example 12 is as follows:
Ag(10nm)/ITO(15nm)/HATCN(10nm)/NPB(30nm)/CBP:15wt％Ir(ppy)3/Bphen (20 nm)/formula (7-1): 10% Ag (10nm)/Ag (10nm)
Example 13
Example 13 provides a top-emission organic electroluminescent device having the following structure:
Ag(10nm)/ITO(15nm)/HATCN(10nm)/NPB(30nm)/CBP:15wt％Ir(ppy)3/Bphen (20 nm)/formula (8-3): 10% Ni (10nm)/Ag (10nm)
Example 14
The structure of the top-emission organic electroluminescent device provided in example 14 is as follows:
Ag(10nm)/ITO(15nm)/HATCN(10nm)/NPB(30nm)/CBP:15wt％Ir(ppy)3/Bphen (20 nm)/formula (8-4): 10% Pt (10nm)/Ag (10nm)
Example 15
Example 15 provides a top-emission organic electroluminescent device having the following structure:
Ag(10nm)/ITO(15nm)/HATCN(10nm)/NPB(30nm)/CBP:15wt％Ir(ppy)3/Bphen (20 nm)/formula (9-1): 10% Cu (10nm)/Ag (10nm)
Watch two
As shown in table two, in examples 4 to 15, coordination compounds formed by electron transport materials of different structural formulas and different inert metals in the examples of the present application were selected as electron injection layers, and the performance of the top emission organic electroluminescent device was better than that of comparative example 1 in which no electron injection layer was used, which indicates that different coordination compounds all have the functions of reducing the injection barrier between the cathode and the electron transport material and improving the electron injection performance.
In order to solve the problem that the quenching probability of the luminescent center of the organic electroluminescent device in the prior art is high, the embodiment of the application also provides a preparation method of the organic electroluminescent device. It should be noted that the preparation method may be used for preparing a top emission organic electroluminescent device, and may also be used for preparing a bottom emission organic electroluminescent device, which is not limited in this application.
The organic electroluminescent device may include a substrate, an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a cathode. The preparation method of the organic electroluminescent device is as follows:
an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a cathode, which are stacked on each other, are sequentially vapor-deposited on a substrate.
The materials of the anode, the hole injection layer, the hole transport layer, the light emitting layer, the electron transport layer and the cathode may all be materials commonly used in the prior art for the anode, the hole injection layer, the hole transport layer, the light emitting layer, the electron transport layer and the cathode in the organic electroluminescent device, and the methods for preparing the anode, the hole injection layer, the hole transport layer, the light emitting layer, the electron transport layer and the cathode in the organic electroluminescent device may also be the prior art, therefore, the process for preparing the anode, the hole injection layer, the hole transport layer, the light emitting layer, the electron transport layer and the cathode is not repeated here, and only how to evaporate the electron injection layer on the electron transport layer is described in detail:
at least one inert metal simple substance and at least one electron transport material are evaporated by adopting a mixed evaporation method, so that at least one coordination compound is formed by the at least one inert metal simple substance and the at least one electron transport material in the evaporation process.
The at least one electron transport material may have coordination capability and comprise N ^ O and/or N ^ N heterocycles.
The at least one simple inert metal and the at least one electron transport material may be the at least one simple inert metal and the at least one electron transport material mentioned in embodiment 1, and the mass ratio of the at least one simple inert metal and the at least one electron transport material may refer to the mass ratio mentioned in embodiment 1, which is not described herein again. The thickness of the electron injection layer may be 5nm to 30 nm.
It should be noted that, after the deposition of each film layer on the substrate is completed, the anode and the cathode may be connected with a conducting wire respectively, and then packaged. The lead connected with the anode is used for being connected with the positive pole of a power supply, and the lead connected with the cathode is used for being connected with the cathode of the power supply.
In one embodiment, when the top-emitting organic electroluminescent device is manufactured by using the above manufacturing method, in order to obtain a good performance of the manufactured top-emitting organic electroluminescent device, a metal reflective layer may be deposited on a substrate substantially before an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode, which are sequentially deposited on the substrate. The anode may be a transparent anode, and the cathode may be a translucent cathode.
The materials of the metal reflective layer, the transparent anode and the semitransparent cathode may all be materials commonly used in the prior art for the metal reflective layer, the transparent anode and the semitransparent cathode in the top-emission organic electroluminescent device, and the method for preparing the metal reflective layer, the transparent anode and the semitransparent cathode in the top-emission organic electroluminescent device may also be the prior art, and details are not repeated here.
In addition, after the metal reflecting layer, the transparent anode, the hole injection layer, the hole transport layer, the luminescent layer, the electron transport layer, the electron injection layer and the semitransparent cathode are evaporated on the substrate, the optical coupling layer can be evaporated on the semitransparent cathode. The material of the optical coupling layer may be a material commonly used in the prior art and applied to an optical coupling layer in a top emission organic electroluminescent device, and is not described herein again. Among them, due to the high reflectivity of the semitransparent cathode electrode, a microcavity effect is introduced into the top-emitting organic electroluminescent device, which causes the color coordinate to change with the time change, and affects the practicability of the top-emitting organic electroluminescent device. In order to improve the optical coupling output characteristic of the top emission structure, an optical coupling layer is evaporated above the semitransparent cathode, and the microcavity effect is adjusted by adjusting the thickness of the optical coupling layer, so that the transmissivity of the semitransparent cathode is effectively improved, and the forward light-emitting efficiency of the top emission organic electroluminescent device is improved.
The coordination compound included in the electron injection layer of the organic electroluminescent device prepared by the preparation method of the organic electroluminescent device provided by the embodiment of the application has stable property, the complexing action between the inert metal ions and the electron transport material is large, and the metal ions are not easy to migrate to the light-emitting layer, so that the problem that the probability of quenching the light-emitting center of the organic electroluminescent device in the prior art is high can be solved.
The organic electroluminescent device prepared by the preparation method of the organic electroluminescent device provided by the embodiment of the application can solve the problem that the probability of quenching of the luminescent center of the organic electroluminescent device in the prior art is high, and can also solve the problems that the organic electroluminescent device in the prior art is low in luminous efficiency, low in production efficiency and low in yield. Specifically, the materials of the electron injection layer of some organic electroluminescent devices in the prior art are active metal simple substances, alkali metal oxides or alkali metal fluorides, and because the active metal is unstable when evaporating the electron injection layers on the electron transport layer, flocculent dust is easily generated, and the flocculent dust can be attached to the electron transport layer, resulting in the unevenness of the prepared electron injection layer, which can result in the lower luminous efficiency of the organic electroluminescent device, and can result in the lower production efficiency and the lower yield of the organic electroluminescent device. By using the preparation method of the organic electroluminescent device provided by the embodiment of the present application, when the electron injection layer is prepared, at least one inert metal simple substance and at least one electron transport material are evaporated by using a hybrid evaporation method, so that at least one coordination compound is formed by the at least one inert metal simple substance and the at least one electron transport material in the evaporation process. The at least one coordination compound is then the material of the electron-injecting layer. Because at least one inert metal simple substance and at least one electron transmission material are not active metals and have stable properties, flocculent dust can not be generated during evaporation, and the flocculent dust can not be attached to the electron transmission layer, so that the unevenness of the electron injection layer can not be caused, the problem that the luminous efficiency of the organic electroluminescent device in the prior art is lower is solved, and the problems that the production efficiency of the organic electroluminescent device is lower and the yield is lower are also solved.
The electron injection layer in the organic electroluminescent device provided by the embodiment of the application comprises a coordination compound formed by at least one inert metal simple substance and at least one electron transport material. Wherein the at least one electron transport material has coordination capability and comprises N ^ O and/or N ^ N heterocycles. The complex included in the electron injection layer has a low work function and is matched with the LUMO level of the electron transport layer, so that an injection barrier of free electrons can be reduced, and the inhibition of injection of free electrons from the cathode into the electron transport layer can be reduced, thereby facilitating injection of free electrons from the cathode into the electron transport layer and reducing the driving voltage. In addition, the coordination compound included in the electron injection layer has stable property, and the complexing action between the inert metal simple substance and the electron transport material is large, so that metal ions are not easy to migrate to the light-emitting layer, thereby solving the problem that the probability of quenching the light-emitting center of the organic electroluminescent device in the prior art is high.
The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (8)
1. An organic electroluminescent device comprises an electron injection layer and an electron transport layer, and is characterized in that the electron injection layer comprises at least one coordination compound formed by an inert metal simple substance and at least one electron transport material, wherein the at least one electron transport material has coordination capacity and contains N ^ O and/or N ^ N and/or O ^ O heterocyclic rings, the LUMO energy level of the electron injection layer and the LUMO energy level of the electron transport layer are matched, the inert metal simple substance is Ag, and the mass ratio of the inert metal simple substance to the at least one electron transport material is 5: 95-25: 75.
2. The organic electroluminescent device of claim 1, wherein the electron transport host material corresponding to the at least one electron transport material is selected from at least one of materials having structural formulas (1) to (12):
wherein R is1、R2、R3、R4、R5、R6、R7、R8Selected from hydrogen radical, alkyl (-C)nH2n+1) Conjugated aromatic group, conjugated heterocyclic ring, methoxy group (-OCH3), amino group and alkyl substituted amino group (-NR)xH2-x) Cyano (-CN) and cyanoalkyl chain (-C)nH2n-CN), halogen (-X) and haloalkyl (-haloalkyl), aldehyde (-OR), and keto (-CHO, -COR)2) And a formylalkyl chain (-C)nH2n-CHO), ester group (-COOR) and ester alkyl chain (-C)nH2n-COOR), or acetylacetonate (-COCH)2COR) and acetylacetonyl alkyl chain (-C)nH2n-COCH2COR), the conjugated aromatic group is phenyl (-Ph), naphthyl or anthryl, and the conjugated heterocyclic ring is pyridyl (-Py) or quinolyl.
3. The organic electroluminescent device according to claim 1, wherein the at least one electron transport material is at least one selected from materials having structural formulae (2-1) to (9-1):
4. the organic electroluminescent device according to claim 1, wherein a volume ratio of the at least one simple inert metal to the at least one electron transport material is 1:99 to 99:1, or a mass ratio of the at least one simple inert metal to the at least one electron transport material is 1:99 to 99: 1.
5. The organic electroluminescent device of claim 1, wherein the mass ratio of the at least one elemental inert metal to the at least one electron transport material is 10: 90.
6. The organic electroluminescent device according to claim 1, wherein the electron injection layer has a thickness of 5nm to 30 nm.
7. A method for preparing an organic electroluminescent device, the organic electroluminescent device comprises a substrate, an anode, a hole injection layer, a hole transport layer, a luminescent layer, an electron transport layer, an electron injection layer and a cathode, and the method comprises the following steps:
the anode, the hole injection layer, the hole transport layer, the light emitting layer, the electron transport layer, the electron injection layer and the cathode which are stacked on each other are sequentially evaporated on the substrate,
when the electron injection layer is evaporated, an inert metal simple substance and at least one electron transport material are evaporated by adopting a hybrid evaporation method, so that the inert metal simple substance and the at least one electron transport material form at least one coordination compound in the evaporation process, wherein the at least one electron transport material has coordination capacity and contains N ^ O and/or N ^ N and/or O heterocycle, the LUMO energy level of the electron injection layer and the LUMO energy level of the electron transport layer are matched, the inert metal simple substance is Ag, and the mass ratio of the inert metal simple substance to the at least one electron transport material is 5: 95-25: 75.
8. The method of manufacturing an organic electroluminescent device according to claim 7, wherein, when the organic electroluminescent device is a top-emission organic electroluminescent device, before the anode, the hole injection layer, the hole transport layer, the light emitting layer, the electron transport layer, the electron injection layer, and the cathode, which are stacked on one another, are sequentially evaporated on the substrate, the method further comprises:
evaporating a metal reflecting layer on the substrate, wherein the anode is a transparent anode, and the cathode is a semitransparent cathode; after evaporating the semi-transparent cathode, evaporating an upper optical coupling layer on the semi-transparent cathode.
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