CN109545997B - Display panel and display device - Google Patents

Display panel and display device Download PDF

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CN109545997B
CN109545997B CN201811512619.5A CN201811512619A CN109545997B CN 109545997 B CN109545997 B CN 109545997B CN 201811512619 A CN201811512619 A CN 201811512619A CN 109545997 B CN109545997 B CN 109545997B
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hole injection
injection layer
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CN109545997A (en
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邱镇
何麟
李梦真
李维维
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Yungu Guan Technology Co Ltd
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/17—Carrier injection layers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/17—Carrier injection layers
    • H10K50/171—Electron injection layers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/30—Devices specially adapted for multicolour light emission
    • H10K59/35—Devices specially adapted for multicolour light emission comprising red-green-blue [RGB] subpixels
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2101/00—Properties of the organic materials covered by group H10K85/00
    • H10K2101/40—Interrelation of parameters between multiple constituent active layers or sublayers, e.g. HOMO values in adjacent layers

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Abstract

The invention discloses a display panel and a display device. The display panel includes: a substrate, and a plurality of organic light emitting units disposed on the substrate; the organic light-emitting unit comprises an anode, a hole injection layer, a hole transport layer, an organic light-emitting layer and a cathode which are arranged in a stacked mode; the hole injection layer comprises at least two sub-hole injection layers, each sub-hole injection layer comprises a hole injection material and a hole transport material, and the volume occupation ratios of the hole injection materials in the at least two sub-hole injection layers are sequentially reduced along the direction from the anode to the hole transport layer. The scheme of the embodiment of the invention reduces the power consumption of the display panel and prolongs the service life of the display panel.

Description

Display panel and display device
Technical Field
The present invention relates to display technologies, and in particular, to a display panel and a display device.
Background
An Organic Light Emitting Diode (OLED) display panel is a self-luminous display panel, and the OLED display panel is increasingly applied to various high-performance display fields due to its advantages of lightness, thinness, high brightness, low power consumption, wide viewing angle, high response speed, and wide temperature range.
However, for the OLED display panel with higher performance requirement, reducing the power consumption of the existing OLED display panel and improving the lifetime of the OLED display panel become the key of research.
Disclosure of Invention
The invention provides an invention name for reducing power consumption of a display panel and prolonging the service life of the display panel.
In a first aspect, an embodiment of the present invention provides a display panel, including:
a substrate, and a plurality of organic light emitting units disposed on the substrate;
the organic light-emitting unit comprises an anode, a hole injection layer, a hole transport layer, an organic light-emitting layer and a cathode which are arranged in a stacked mode;
the hole injection layer comprises at least two sub-hole injection layers, each sub-hole injection layer comprises a hole injection material and a hole transport material, and the volume occupation ratios of the hole injection materials in the at least two sub-hole injection layers are sequentially reduced along the direction from the anode to the hole transport layer.
Optionally, the material used for the hole transport layer is the same as the material used for the hole transport layer.
Optionally, the volume fraction of the hole injection material in the sub-hole injection layer is greater than or equal to 1% and less than or equal to 5%.
Optionally, the hole transport material comprises N, N ' -diphenyl-N, N ' - (1-naphthyl) -1,1' -biphenyl-4, 4' -diamine and/or 4,4' -tris [ 2-naphthylphenylamino ] triphenylamine, and the volume proportion of N, N ' -diphenyl-N, N ' - (1-naphthyl) -1,1' -biphenyl-4, 4' -diamine in the hole transport material is 0% -100%;
the hole injection material comprises 7,7,8, 8-tetracyanoterephthalquinodimethane.
Optionally, the total thickness T1 of the hole injection layer has a value range of: t1 is more than or equal to 5nm and less than or equal to 20 nm.
Optionally, the organic light emitting unit comprises a first sub-hole injection layer and a second sub-hole injection layer, the first sub-hole injection layer being disposed between the second sub-hole injection layer and the anode;
the volume proportion of the hole injection material in the first sub-hole injection layer is greater than or equal to 3% and less than or equal to 5%;
the volume ratio of the hole injection material in the second sub-hole injection layer is greater than or equal to 1% and less than 3%.
Optionally, the organic light emitting unit further comprises an electron transport layer and an electron injection layer disposed between the organic light emitting layer and the cathode, the electron transport layer being disposed between the electron injection layer and the organic light emitting layer;
the electron injection layer comprises at least two sub-electron injection layers, and each sub-electron injection layer comprises an electron transport material and an electron injection main body material; along the direction that the cathode points to the electron transport layer, the volume ratio of the electron transport materials in the at least two sub-electron injection layers is increased in sequence.
Optionally, the volume of the electron injection host material in the sub-electron injection layer is greater than or equal to 10% and less than or equal to 70%.
Optionally, the electron injecting host material comprises ytterbium or lithium fluoride; the electron transport material comprises lithium 8-hydroxyquinoline.
Optionally, the total thickness T2 of the electron injection layer ranges from 1nm < T2 ≤ 2 nm.
In a second aspect, an embodiment of the present invention further provides a display device, where the display device includes the display panel according to any embodiment of the present invention.
According to the embodiment of the invention, at least two sub-hole injection layers are arranged, and the volume ratio of hole injection materials in the at least two sub-hole injection layers is sequentially reduced along the direction from the anode to the hole transport layer, so that the HOMO energy level difference between the sub-hole injection layer and the hole transport layer is gradually reduced along the direction from the anode to the hole transport layer, and the injection barrier of holes between the sub-hole injection layer and the hole transport layer can be buffered. On one hand, the oxidation/reduction reaction of the holes at the interface between the hole transport layer and the sub-hole injection layer can be slowed down, the rise of driving pressure is delayed, the rise of power consumption of the display panel is delayed, and the service life of the display panel is prolonged; on the other hand, the hole injection efficiency can be improved, the hole amount reaching the organic light-emitting layer is increased, the recombination amount of holes and electrons is improved, the light-emitting efficiency of the organic light-emitting unit is improved, the driving voltage required by reaching the preset brightness is reduced, the power consumption of the display panel is further reduced, and the service life of the display panel is prolonged.
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Fig. 1 is a schematic diagram of a display panel according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of an organic light emitting unit according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of another organic light-emitting unit provided by an embodiment of the present invention;
FIG. 4 is a schematic diagram of another organic light-emitting unit provided in an embodiment of the present invention;
FIG. 5 is a schematic diagram of another organic light-emitting unit provided by an embodiment of the present invention;
fig. 6 is a schematic diagram of still another organic light emitting unit provided by an embodiment of the present invention;
fig. 7 is a schematic diagram of a display device according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
The organic light emitting unit of the OLED display panel includes a cathode, an anode, and an organic light emitting layer. When a voltage is applied across the cathode and the anode of the organic light emitting unit, carriers in the organic light emitting unit are injected from the anode and the cathode, respectively, into the organic light emitting layer to recombine to emit light. Since the energy levels of different film layers are different, an injection barrier exists at the interface of different film layers. With the increase of the service time, the carriers are accumulated at the interface of the film layer, and the oxidation/reduction on the interface is continuously carried out, so that the interface barrier is continuously increased, and the driving voltage is increased. The increase in the driving voltage inevitably causes the power consumption of the display panel to increase, thereby causing a reduction in lifetime.
To solve the above problem, the present embodiment provides a display panel including:
a substrate, and a plurality of organic light emitting units disposed on the substrate;
the organic light-emitting unit comprises an anode, a hole injection layer, a hole transport layer, an organic light-emitting layer and a cathode which are arranged in a stacked mode;
the hole injection layer comprises at least two sub-hole injection layers, each sub-hole injection layer comprises a hole injection material and a hole transport material, and the volume occupation ratios of the hole injection materials in the at least two sub-hole injection layers are sequentially reduced along the direction from the anode to the hole transport layer.
Specifically, at least two layers of sub-hole injection layers are arranged, and the volume ratio of hole injection materials in the at least two layers of sub-hole injection layers is sequentially reduced along the direction from the anode to the hole transport layer, so that the HOMO energy level difference between the sub-hole injection layers and the hole transport layer is gradually reduced along the direction from the anode to the hole transport layer, and the injection barrier of holes between the sub-hole injection layers and the hole transport layer can be buffered. On one hand, the oxidation/reduction reaction of the holes at the interface between the hole transport layer and the sub-hole injection layer can be slowed down, the rise of driving pressure is delayed, the rise of power consumption of the display panel is delayed, and the service life of the display panel is prolonged; on the other hand, the hole injection efficiency can be improved, the hole amount reaching the organic light-emitting layer is increased, the recombination amount of holes and electrons is improved, the light-emitting efficiency of the organic light-emitting unit is improved, the driving voltage required by reaching the preset brightness is reduced, the power consumption of the display panel is further reduced, and the service life of the display panel is prolonged.
In the present invention, the volume ratio of the hole injection material in the sub-hole injection layer means the volume ratio of the hole injection material in the "sub-hole injection layer" based on 100% of the total volume of the individual "sub-hole injection layers". In the present invention, the volume ratio can be calculated in the following two ways: in the first mode, when the sub-hole injection layer is prepared, the film thickness of the hole injection material and the hole transport material evaporated on the substrate is monitored through a crystal oscillator and a film thickness meter, and then the volume proportion of the hole injection material in the sub-hole injection layer is obtained. And secondly, verifying the volume ratio of the hole injection material in the sub-hole injection layer by adopting a scanning electron microscope, element content analysis and other testing means.
Fig. 1 is a schematic diagram of a display panel according to an embodiment of the present invention, and referring to fig. 1, the display panel includes:
a substrate 10, and a plurality of organic light emitting units 20 disposed on the substrate 10;
the organic light emitting unit 20 includes an anode 21, a first sub-hole injection layer 221, a second sub-hole injection layer 222, an … … nth sub-hole injection layer 22n, a hole transport layer 23, an organic light emitting layer 24, and a cathode 25, which are stacked; wherein n is a positive integer greater than or equal to 2;
each of the sub-hole injection layers includes a hole injection material and a hole transport material, and the volume fractions of the hole injection materials in the first sub-hole injection layer 221, the second sub-hole injection layers 222, … …, and the n-th sub-hole injection layer 22n decrease in order in the direction from the anode 21 toward the hole transport layer 23.
Specifically, the first sub-hole injection layer 221, the second sub-hole injection layers 222, … …, and the n-th sub-hole injection layer 22n adopt the same material composition, that is, all include the same hole transport material and hole injection material, and the volume occupancy ratios of the hole injection materials in the first sub-hole injection layer 221, the second sub-hole injection layer 222 … …, and the n-th sub-hole injection layer 22n are sequentially reduced, so that the HOMO level differences of the first sub-hole injection layer 221, the second sub-hole injection layers 222, … …, and the n-th sub-hole injection layer 22n and the hole transport layer 23 are gradually reduced, and the volume occupancy ratio of the hole injection material in the n-th sub-hole injection layer 22n can be set smaller, so that the HOMO level difference of the n-th sub-hole injection layer 22n and the hole transport layer 23 is smaller, the injection barrier of holes between the sub-hole injection layer and the hole transport layer 23 can be reduced, the hole injection efficiency is improved. On one hand, the improvement of the hole injection efficiency reduces the accumulation of holes at the interface between the hole transport layer and the sub-hole injection layer, thereby slowing down the oxidation/reduction reaction at the interface, delaying the rise of the driving pressure, delaying the rise of the power consumption of the display panel and prolonging the service life of the display panel; on the other hand, the hole injection efficiency is improved, the hole amount reaching the organic light-emitting layer can be increased, the recombination amount of holes and electrons is improved, the light-emitting efficiency of the organic light-emitting unit is improved, the driving voltage required by reaching the preset brightness is reduced, the power consumption of the display panel is further reduced, and the service life of the display panel is prolonged.
In addition, the hole transport material and the hole transport layer 23 may be the same material, and since the volume ratio of the hole injection material in the nth sub-hole injection layer 22n is smaller, the materials of the nth sub-hole injection layer 22n and the hole transport layer are closer, so that the oxidation/reduction reaction at the interface can be further slowed down, thereby delaying the increase of the power consumption of the display panel and improving the service life of the display panel.
Optionally, the volume fraction of the hole injection material in the sub-hole injection layer is greater than or equal to 1% and less than or equal to 5%.
Specifically, the sub-hole injection layer is used for injecting holes, and the volume ratio of the hole injection material in the sub-hole injection layer is too small, which easily causes the hole injection amount to decrease, so that the hole amount reaching the organic light emitting layer 24 is too small, which causes the organic light emitting unit 20 to have low light emitting efficiency; the volume ratio of the hole injection material in the sub-hole injection layer is too large, which easily causes imbalance of the injection amount of holes and electrons, affects the stability of the organic light emitting unit 20, and makes the HOMO energy level difference between the sub-hole injection layer and the hole transport layer 23 too large to be beneficial to hole injection. By setting the volume ratio of the hole injection material in the sub-hole injection layer to be greater than or equal to 1% and less than or equal to 5%, it is ensured that the organic light-emitting unit 20 has a high hole injection amount, and the HOMO level difference between the sub-hole injection layer and the hole transport layer 23 is small, so that the hole injection efficiency can be further improved, the power consumption of the display panel can be reduced, and the service life of the display panel can be prolonged.
Alternatively, the hole transport material includes N, N ' -diphenyl-N, N ' - (1-naphthyl) -1,1' -biphenyl-4, 4' -diamine (CAS No.123847-85-8) and/or 4,4',4 ″ -tris [ 2-naphthylphenylamino ] triphenylamine 4,4,4 tris (2-naphthylphenylamino) triphenylamine (CAS No. 185690-41-9); the hole injection material includes 7,7,8, 8-tetracyanoterephthalquinodimethane (CAS No. 1518-16-7).
Specifically, the present embodiment only shows some hole transport materials and hole injection materials by way of example, and is not a limitation to the present invention, and other materials may be used in other embodiments.
Optionally, the total thickness T1 of the hole injection layer has a value range of: t1 is more than or equal to 5nm and less than or equal to 20 nm.
In which the anode 21 and the cathode 25 of the organic light emitting unit 20 constitute an optical microresonator, i.e., a microcavity. The layers between the anode 21 and the cathode 25 and the layers between the anode 21 and the cathode 25The total thickness is the cavity length of the microcavity. In the microcavity, only the wavelength λ satisfies
Figure BDA0001901175650000071
Will be enhanced and the rest will be diminished. Wherein k x λ 2LeffK is the number of microcavity stages, nmAnd dmRefractive index and thickness, θ, of the mth layer in the microcavity0Is a luminous angle, LeffIs an effective optical path of phi1(lambda) and phi2(λ) is the reflection phase shift of the anode 21 and cathode 25, respectively. The total thickness T1 of the hole injection layer can be adjusted according to the wavelength of the light emitted by the organic light-emitting unit 20, so that the microcavity length of the organic light-emitting unit 20 satisfies the above formula, and the light emitted by the organic light-emitting unit 20 satisfies the color requirement of the display panel. Illustratively, the total thickness T1 of the sub-hole injection layer may be set to be 5nm, 10nm, 15nm, or the like.
Fig. 2 is a schematic structural diagram of an organic light emitting unit according to an embodiment of the present invention, and optionally, referring to fig. 2, the thickness of the n-layer sub-hole injection layer is gradually decreased along a direction from the anode 21 to the hole transport layer 23. The thickness of the first sub-hole injection layer 221 is T11, the thickness of the second sub-hole injection layer 222 is T12 … …, the thickness of the nth sub-hole injection layer 22n is T1n, and T11 > T12 > … > T1 n.
Specifically, by setting the thickness of the n sub-hole injection layers to be gradually reduced, the residence time of the holes on each sub-hole injection layer is sequentially reduced along the direction from the anode 21 to the organic light-emitting layer 24, which is beneficial to reducing the loss of the holes on the path from the anode 21 to the organic light-emitting layer 24 and further beneficial to improving the hole injection efficiency.
In addition, the organic light emitting unit 20 may include a red organic light emitting unit, a green organic light emitting unit, and a blue organic light emitting unit, and the number of the sub-hole injection layers provided in the organic light emitting units of different light emitting colors may be the same or different.
Fig. 3 is a schematic view of still another organic light emitting unit provided by an embodiment of the present invention, and alternatively, referring to fig. 3, the organic light emitting unit 20 includes a first sub-hole injection layer 221 and a second sub-hole injection layer 222, and the first sub-hole injection layer 221 is disposed between the second sub-hole injection layer 222 and the anode 21;
the volume ratio of the hole injection material in the first sub-hole injection layer 221 is greater than or equal to 3% and less than or equal to 5%;
the volume ratio of the hole injection material in the second sub-hole injection layer 222 is greater than or equal to 1% and less than 3%.
Specifically, the first sub-hole injection layer 221 ensures that the organic light emitting unit 20 has a higher total hole injection amount, and the second sub-hole injection layer 222 reduces the HOMO level difference with the hole transport layer 23, thereby improving the hole injection efficiency, reducing the power consumption of the display panel, and prolonging the service life of the display panel.
In addition, by providing two sub-hole injection layers, the organic light emitting unit 20 can be ensured to have a smaller thickness, so that the display panel can be ensured to have a smaller thickness, and the development trend of being light and thin is met.
It should be noted that the specific volume ratio of the hole injection material in the first sub-hole injection layer 221 and the second sub-hole injection layer 222 may be set according to needs, and the embodiment is not particularly limited, and may be set to 3% and 1% for example, respectively.
Fig. 4 is a schematic view of still another organic light emitting unit provided by an embodiment of the present invention, and alternatively, referring to fig. 4, the display panel includes a first sub-hole injection layer 221, a second sub-hole injection layer 222, and a third sub-hole injection layer 223 sequentially stacked, the first sub-hole injection layer 221 being disposed between the second sub-hole injection layer 222 and the anode 21;
the volume ratio of the hole injection material in the first sub-hole injection layer 221 is greater than or equal to 3% and less than or equal to 5%;
the volume ratio of the hole injection material in the second sub-hole injection layer 222 is greater than or equal to 2% and less than 3%;
the volume ratio of the hole injection material in the third sub-hole injection layer 223 is 1% or more and less than 2%.
Specifically, the first sub-hole injection layer 221 ensures that the organic light emitting unit 20 has a higher total hole injection amount, and the second sub-hole injection layer 222 and the third sub-hole injection layer 223 reduce the HOMO level difference with the hole transport layer 23, thereby improving the hole injection efficiency, reducing the power consumption of the display panel, and prolonging the service life of the display panel. By arranging three sub-hole injection layers, the HOMO energy level difference between the sub-hole injection layers and the energy level difference between the third sub-hole injection layer 223 and the hole transport layer 23 are smaller, so that the injection barrier between the sub-hole injection layer and the hole transport layer 23 can be better buffered, more holes are injected into the hole transport layer 23, and the holes reach the organic light emitting layer 24.
It should be noted that the specific volume ratio of the hole injection material in the first sub-hole injection layer 221, the second sub-hole injection layer 222, and the third sub-hole injection layer 223 may be set according to needs, and this embodiment is not particularly limited, and may be set to 3%, 2%, and 1% for example, or may be set to 5%, 3%, and 1% for example.
Fig. 5 is a schematic diagram of another organic light emitting unit provided in an embodiment of the present invention, and optionally, referring to fig. 5, the organic light emitting unit 20 further includes:
an electron transport layer 26 and an electron injection layer disposed between the organic light emitting layer 24 and the cathode 25, the electron transport layer 26 being disposed on a side of the electron injection layer (271, 272 … … 27m) adjacent to the organic light emitting layer 24;
the electron injection layer includes at least two sub-electron injection layers (271, 272 … … 27m), each of which includes an electron transport material and an electron injection host material; the volume fraction of the electron transport material in at least two of the sub-electron injection layers (271, 272 … … 27m) increases in order in the direction from the cathode 25 toward the electron transport layer 26.
Specifically, referring to fig. 5, the organic light emitting unit 20 includes a first sub electron injection layer 271, a second sub electron injection layer 272 … …, and an mth sub electron injection layer 27m, where m is a positive integer of 2 or more, the first sub electron injection layer 271 is disposed between the second sub electron injection layer 272 and the cathode 25, and the volume fractions of the electron transport materials in the first sub electron injection layer 271, the second sub electron injection layer 272 … …, and the mth sub electron injection layer 27m sequentially increase.
In the present invention, the volume ratio of the electron injection host material in each of the sub-electron injection layers is greater than or equal to 10%, and less than or equal to 70%, preferably greater than or equal to 30%, and less than or equal to 70%, more preferably greater than or equal to 30%, and less than or equal to 50%.
Specifically, by arranging at least two sub-electron injection layers, and along the direction from the cathode 25 to the electron transport layer 26, the volume ratio of electron transport materials in the at least two sub-electron injection layers is sequentially increased, so that along the direction from the cathode 25 to the electron transport layer 26, the LUMO energy level difference between the sub-electron injection layer and the electron transport layer is gradually reduced, an injection barrier of electrons between the sub-electron injection layer and the electron transport layer 26 can be buffered, the electron injection efficiency is improved, the amount of electrons reaching the organic light emitting layer 24 can be increased, the recombination amount of holes and electrons is improved, the light emitting efficiency of the organic light emitting unit is further improved, the power consumption of the display panel is further reduced, and the service life of the display panel is prolonged.
Optionally, the electron injecting host material comprises ytterbium or lithium fluoride; the electron transport material comprises lithium 8-hydroxyquinoline.
Specifically, the cathode 25 may use a metal having a low work function to improve the luminance and efficiency of the organic light emitting unit 20. In order to make the fermi level of the cathode 25 have a smaller energy level difference from the LUMO level of the first sub-electron injection layer 271, a metal material having the same or similar fermi level as that of the material of the cathode 25 may be used as the electron injection host material of the sub-electron injection layer, for example, the electron injection host material of the sub-electron injection layer may include metal ytterbium (Yb).
In addition, since the inorganic insulating material generally has high stability, the stability of the organic light emitting unit 20 can be improved by using the inorganic insulating layer as a sub-electron injection layer between the cathode 25 and the organic light emitting layer 24 of the organic light emitting unit. The material of the inorganic insulating layer as the sub-electron injection layer may be, for example, LiF, MgO, Al2O3And the like. Therefore, the electron injecting host material of the sub-electron injecting layer may also be selected to include lithium fluoride (LiF).
Accordingly, the electron transport material may be selected from the same materials as those used for the electron transport layer 26 to reduce the energy level difference between the electron injection layer and the electron transport layer 26, and exemplary 8-hydroxyquinoline lithium (Liq) may be selected.
Fig. 6 is a schematic diagram of still another organic light emitting unit according to an embodiment of the present invention, and optionally, referring to fig. 6, the organic light emitting unit 20 includes two sub-electron injection layers, that is, a first sub-electron injection layer 271 and a second sub-electron injection layer 272, the first sub-electron injection layer 271 is disposed between the second sub-electron injection layer 272 and the cathode 25, the material of the first sub-electron injection layer 271 may be selected to include an electron injection host material and an electron transport material, and a ratio of the electron injection host material to the electron transport material is 3:2 (a volume ratio of the electron transport material is 40%), for example, ytterbium: lithium 8-hydroxyquinoline (Yb: Liq) ═ 3:2, or lithium fluoride: lithium 8-hydroxyquinoline (LiF: Liq) ═ 3: 2. (ii) a The material of the second sub-electron injection layer 272 may be selected to include an electron injection host material and an electron transport material, and the ratio of the electron injection host material to the electron transport material is 1:1 (the volume ratio of the electron transport material is 50%), such as ytterbium: lithium 8-hydroxyquinoline (Yb: Liq) ═ 1:1, or lithium fluoride: lithium 8-hydroxyquinoline (LiF: Liq) ═ 1: 1.
Alternatively, referring to FIGS. 5 and 6, the total thickness T2 of the electron injection layer ranges from 1nm < T2 ≦ 2 nm. Namely, the sum of the thicknesses of the first sub-electron injection layer 271, the second sub-electron injection layers 272 and …, and the mth sub-electron injection layer 27m has a value range of 1nm < T2 < 2 nm. Specifically, by setting the sub-electron injection layer to be thinner, the thickness of the sub-electron injection layer in the direction in which the cathode 25 points to the organic light emitting layer 24 can be reduced, thereby reducing the residence time of electrons in the LUMO level of each sub-electron injection layer, which is beneficial to reducing the loss of electrons in the sub-electron injection layer, and is further beneficial to injecting more electrons into the organic light emitting layer 24. The specific value of the total thickness T2 of the sub-electron injection layer can be determined according to the microcavity
Figure BDA0001901175650000121
And (4) determining.
Alternatively, referring to fig. 6, when the sub electron injection layer 14 includes two sub electron injection layers, i.e., the first sub electron injection layer 271 and the second sub electron injection layer 272, the thickness T21 of the first sub electron injection layer 271 is in a range of 0.5nm < T21 < 1nm, and the thickness T22 of the second sub electron injection layer 272 is in a range of 0.5nm < T22 < 1 nm. So configured, when the sub electron injection layer includes two sub electron injection layers, it is also possible to efficiently transport electrons from the sub electron injection layer to the organic light emitting layer 24.
Alternatively, referring to fig. 6, the thicknesses of at least two sub electron injection layers are sequentially decreased in a direction in which the cathode 25 is directed to the electron transport layer 26.
Specifically, by setting the thicknesses of the sub-electron injection layers to be sequentially decreased, the residence time of electrons on the sub-electron injection layers is sequentially decreased in the direction in which the electrons point to the organic light emitting layer 24 from the cathode 25, which is beneficial to reducing the loss of electrons on the path from the cathode 25 to the organic light emitting layer 24, and further beneficial to injecting more electrons into the organic light emitting layer 24, thereby improving the light emitting efficiency.
In addition, it should be noted that the specific type of the display panel is not specifically limited in this embodiment, the scheme of this embodiment may be applied to any display panel related to the transmission process of electrons and holes, and the exemplary display panel may be an OLED display panel, a quantum dot light emitting diode QLED display panel, a micro light emitting diode micro led display panel, or a stretched OLED display panel.
Simulation test example
Comparative example (non-prior art)
A display panel comprises a substrate and a plurality of organic light-emitting units arranged on the substrate, wherein each organic light-emitting unit comprises an anode, a hole injection layer, a hole transport layer, an organic light-emitting layer, an electron transport layer, an electron injection layer and a cathode which are arranged in a stacked mode.
Wherein, the anode material is RGO, and the cathode material is metallic silver. The thickness of the hole injection layer is 20nm, and the material is 7,7,8, 8-tetracyano-p-quinodimethane; the thickness of the hole transport layer was 80nm, and the materials were N, N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine and 4,4 '-tris [ 2-naphthylphenylamino ] triphenylamine, wherein the volume ratio of N, N' -diphenyl-N, N '- (1-naphthyl) -1,1' -biphenyl-4, 4 '-diamine to 4,4' -tris [ 2-naphthylphenylamino ] triphenylamine was 1: 1. The material of the electron injection layer is lithium fluoride with the thickness of 1.8nm, and the material of the electron transport layer is 8-hydroxyquinoline lithium with the thickness of 2 nm.
The time required for the driving pressure to rise by 0.1V was found to be 570h by testing of setfos optical simulation software.
Example 1: with reference to the comparative example, the difference is: the hole injection layer is provided as two sub-hole injection layers, the first sub-hole injection layer being provided between the second sub-hole injection layer and the anode.
The first sub-hole injection layer is 12nm thick and contains a hole injection material 7,7,8, 8-tetracyano-p-benzoquinodimethane and a hole transport material N, N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine, wherein the volume of the hole injection material in the first sub-hole injection layer is 5%.
The second sub-hole injection layer is 8nm thick and contains a hole injection material 7,7,8, 8-tetracyano-p-phenylenediquinone dimethane and a hole transport material N, N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine, wherein the volume of the hole injection material in the second sub-hole injection layer is 3%.
As a result of simulation test, compared with the display panel of the comparative example, the display panel of example 1 has a prolonged driving voltage rise of 0.1V by about 200 hours and a prolonged lifetime by about 40%.
Example 2: with reference to the comparative example, the difference is: the hole injection layer is provided as two sub-hole injection layers, and the electron injection layer is provided as two sub-electron injection layers. The anode, the first sub-hole injection layer, the second sub-electron injection layer, the first sub-electron injection layer and the cathode are sequentially arranged in the direction from the anode to the cathode.
The first sub-hole injection layer is 12nm thick and contains a hole injection material 7,7,8, 8-tetracyano-p-benzoquinodimethane and a hole transport material N, N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine, wherein the volume of the hole injection material in the first sub-hole injection layer is 5%.
The second sub-hole injection layer is 8nm thick and contains a hole injection material 7,7,8, 8-tetracyano-p-phenylenediquinone dimethane and a hole transport material N, N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine, wherein the volume of the hole injection material in the second sub-hole injection layer is 3%.
The thickness of the first sub-electron injection layer is 1nm, and the first sub-electron injection layer contains an electron injection main body material lithium fluoride and an electron transport material 8-hydroxyquinoline lithium, wherein the volume ratio of the electron injection main body material in the first sub-electron injection layer is 40%.
The thickness of the second sub-electron injection layer is 0.8nm, and the second sub-electron injection layer contains an electron injection main body material lithium fluoride and an electron transport material 8-hydroxyquinoline lithium, wherein the volume of the electron injection main body material in the second sub-electron injection layer is 30%.
As a result of simulation test, compared with the display panel of the comparative example, the display panel of example 2 has a prolonged driving voltage rise time of 0.1V by about 300h and a prolonged lifetime by about 55%.
Example 3: with reference to the comparative example, the difference is: the hole injection layer is provided as three sub-hole injection layers, and the anode, the first sub-hole injection layer, the second sub-hole injection layer and the third sub-hole injection layer are sequentially arranged from the anode to the direction of the light-emitting element.
The first sub-hole injection layer is 8nm thick and contains a hole injection material 7,7,8, 8-tetracyano-p-benzoquinodimethane and a hole transport material N, N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine, wherein the volume of the hole injection material in the first sub-hole injection layer is 5%.
The second sub-hole injection layer is 7nm thick and contains a hole injection material 7,7,8, 8-tetracyano-p-benzoquinodimethane and a hole transport material N, N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine, wherein the volume of the hole injection material in the second sub-hole injection layer is 3%.
The third sub-hole injection layer is 5nm thick and contains a hole injection material 7,7,8, 8-tetracyano-p-benzoquinodimethane and a hole transport material N, N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine, wherein the volume of the hole injection material in the third sub-hole injection layer is 1%.
As a result of simulation test, compared with the display panel of the comparative example, the display panel of example 3 has a prolonged driving voltage rise of 0.1V by about 400 hours and a prolonged lifetime by about 50%.
Example 4: with reference to the comparative example, the difference is: the hole injection layer is provided as three sub-hole injection layers, and the electron injection layer is provided as two sub-electron injection layers. The anode, the first sub-hole injection layer, the second sub-hole injection layer, the third sub-hole injection layer, the second sub-electron injection layer, the first sub-electron injection layer and the cathode are sequentially arranged in a direction from the anode to the cathode.
The first sub-hole injection layer is 8nm thick and contains a hole injection material 7,7,8, 8-tetracyano-p-benzoquinodimethane and a hole transport material N, N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine, wherein the volume of the hole injection material in the first sub-hole injection layer is 3%.
The second sub-hole injection layer is 7nm thick and contains a hole injection material 7,7,8, 8-tetracyano-p-benzoquinodimethane and a hole transport material N, N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine, wherein the volume ratio of the hole injection material in the second sub-hole injection layer is 2%.
The third sub-hole injection layer is 5nm thick and contains a hole injection material 7,7,8, 8-tetracyano-p-benzoquinodimethane and a hole transport material N, N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine, wherein the volume of the hole injection material in the third sub-hole injection layer is 1%.
The thickness of the first sub-electron injection layer is 1nm, and the first sub-electron injection layer contains an electron injection main body material lithium fluoride and an electron transport material 8-hydroxyquinoline lithium, wherein the volume ratio of the electron injection main body material in the first sub-electron injection layer is 40%.
The thickness of the second sub-electron injection layer is 0.8nm, and the second sub-electron injection layer contains an electron injection main body material lithium fluoride and an electron transport material 8-hydroxyquinoline lithium, wherein the volume of the electron injection main body material in the second sub-electron injection layer is 30%.
As a result of simulation test, the time required for the driving voltage of the display panel in example 4 to rise by 0.1V was prolonged by about 900 hours and the lifetime of the display panel was improved by about 60% as compared with the display panel in the comparative example.
Fig. 7 is a schematic diagram of a display device according to an embodiment of the present invention, and referring to fig. 7, the display device 100 includes a display panel 200 according to any embodiment of the present invention. The display device 100 may be an electronic display device such as a mobile phone and a tablet computer.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious modifications, rearrangements, combinations and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims (11)

1. A display panel, comprising:
a substrate, and a plurality of organic light emitting units disposed on the substrate;
the organic light-emitting unit comprises an anode, a hole injection layer, a hole transport layer, an organic light-emitting layer and a cathode which are arranged in a stacked mode;
the hole injection layer comprises at least two sub-hole injection layers, each sub-hole injection layer comprises a hole injection material and a hole transport material, and the volume occupation ratios of the hole injection materials in the at least two sub-hole injection layers are sequentially reduced along the direction from the anode to the hole transport layer; and the thickness of the sub-hole injection layer is gradually reduced from the anode to the direction of the hole transport layer.
2. The display panel according to claim 1, characterized in that:
the material adopted by the hole transport layer and the hole transport material are the same material.
3. The display panel according to claim 1, characterized in that:
the volume ratio of the hole injection material in the sub-hole injection layer is greater than or equal to 1% and less than or equal to 5%.
4. The display panel according to claim 1, characterized in that:
the hole transport material comprises N, N ' -diphenyl-N, N ' - (1-naphthyl) -1,1' -biphenyl-4, 4' -diamine and/or 4,4' -tris [ 2-naphthylphenylamino ] triphenylamine;
the hole injection material comprises 7,7,8, 8-tetracyanoterephthalquinodimethane.
5. The display panel according to claim 1, characterized in that:
the total thickness T1 of the hole injection layer has a value range of: t1 is more than or equal to 5nm and less than or equal to 20 nm.
6. The display panel according to claim 3, wherein:
the organic light-emitting unit comprises a first sub-hole injection layer and a second sub-hole injection layer, wherein the first sub-hole injection layer is arranged between the second sub-hole injection layer and the anode;
the volume proportion of the hole injection material in the first sub-hole injection layer is greater than or equal to 3% and less than or equal to 5%;
the volume ratio of the hole injection material in the second sub-hole injection layer is greater than or equal to 1% and less than 3%.
7. The display panel according to any one of claims 1 to 6, wherein:
the organic light emitting unit further includes an electron transport layer and an electron injection layer disposed between the organic light emitting layer and the cathode, the electron transport layer being disposed between the electron injection layer and the organic light emitting layer;
the electron injection layer comprises at least two sub-electron injection layers, and each sub-electron injection layer comprises an electron transport material and an electron injection main body material; along the direction that the cathode points to the electron transport layer, the volume ratio of the electron transport materials in the at least two sub-electron injection layers is increased in sequence.
8. The display panel according to claim 7, wherein:
the volume of the electron injection main body material in each sub-electron injection layer is greater than or equal to 10% and less than or equal to 70%.
9. The display panel according to claim 7, wherein:
the electron injection host material comprises ytterbium or lithium fluoride; the electron transport material comprises lithium 8-hydroxyquinoline.
10. The display panel according to claim 7, wherein:
the value range of the total thickness T2 of the electron injection layer is more than 1nm and less than or equal to T2 and less than or equal to 2 nm.
11. A display device characterized by comprising the display panel according to any one of claims 1 to 10.
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