CN113437231B - Display panel and display device - Google Patents

Display panel and display device Download PDF

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Publication number
CN113437231B
CN113437231B CN202110690577.XA CN202110690577A CN113437231B CN 113437231 B CN113437231 B CN 113437231B CN 202110690577 A CN202110690577 A CN 202110690577A CN 113437231 B CN113437231 B CN 113437231B
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transport material
hole
transport
display panel
layer
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CN113437231A (en
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颜志敏
韩建厅
刘俊伟
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Yungu Guan Technology Co Ltd
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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]
    • H10K50/14—Carrier transporting layers
    • H10K50/15—Hole transporting 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
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • 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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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Electroluminescent Light Sources (AREA)

Abstract

An embodiment of the present invention provides a display panel and a display device, where the display panel includes: the light emitting diode comprises a first electrode, a second electrode and a light emitting structure layer positioned between the first electrode and the second electrode, wherein the light emitting structure layer comprises: a light emitting layer; and the hole transport layer is positioned between the light emitting layer and the first electrode, the material of the hole transport layer comprises a first hole transport material, wherein the first hole transport material at least comprises a first transport material and a second transport material, the highest occupied molecular orbital energy level of the first transport material is greater than that of the second transport material, and the hole mobility of the first transport material is greater than that of the second transport material. According to the embodiment of the invention, the hole transport layer of the display panel is made of the first transport material and the second transport material, so that the service life of devices of the display panel can be prolonged, and the power consumption of the display panel can be reduced.

Description

Display panel and display device
Technical Field
The invention relates to the technical field of display, in particular to a display panel and a display device.
Background
Organic Light-Emitting diodes (OLEDs) are active Light-Emitting devices. Compared with the traditional Liquid Crystal Display (LCD) Display mode, the OLED Display technology does not need a backlight lamp and has the self-luminous characteristic. The OLED adopts a thin organic material film layer and a glass substrate, and when a current flows, the organic material can emit light. Therefore, the OLED display panel can save electric energy remarkably, can be made lighter and thinner, can endure a wider range of temperature variation than the LCD display panel, and has a larger visual angle. The OLED display panel is expected to become a next-generation flat panel display technology following the LCD, and is one of the technologies that receives the most attention among the flat panel display technologies at present.
Efficiency, voltage and lifetime are a pair of criteria that are difficult to compromise for OLED display panels.
Disclosure of Invention
The embodiment of the invention provides a display panel and a display device, aiming at improving the luminous efficiency of the display panel and reducing the power consumption of the display panel.
An embodiment of a first aspect of the present invention provides a display panel, including: the light emitting diode comprises a first electrode, a second electrode and a light emitting structure layer positioned between the first electrode and the second electrode, wherein the light emitting structure layer comprises: a light emitting layer; and the hole transport layer is positioned between the light emitting layer and the first electrode, the material of the hole transport layer comprises a first hole transport material, wherein the first hole transport material at least comprises a first transport material and a second transport material, the highest occupied molecular orbital energy level of the first transport material is greater than that of the second transport material, and the hole mobility of the first transport material is greater than that of the second transport material.
According to an embodiment of the first aspect of the present invention, at least one of the first transport material and the second transport material has a hole mobility greater than or equal to a first predetermined hole mobility, and the hole mobility of the first transport material and the second transport material after mixing is greater than or equal to ninety percent of the first predetermined hole mobility.
According to one embodiment of the first aspect of the present invention, the first predetermined hole mobility is 10 -5 cm 2 /vs。
According to any one of the preceding embodiments of the first aspect of the present invention, the difference in the highest occupied molecular orbital energy levels of the first transport material and the second transport material is less than or equal to 0.05eV.
According to any one of the preceding embodiments of the first aspect of the present invention, at least one of the first transport material and the second transport material has a highest occupied molecular orbital level of less than or equal to-5.1 eV.
According to any one of the preceding embodiments of the first aspect of the present invention, the first transport material and the second transport material are mixed in a ratio of 0.4 to 2.4.
According to any one of the preceding embodiments of the first aspect of the present invention, the first and second transport materials are mixed in a ratio of 1:1.
According to any one of the preceding embodiments of the first aspect of the present invention, the first transport material has a highest occupied molecular orbital level of-5.15 eV and the second transport material has a highest occupied molecular orbital level of-5.18 eV.
According to any one of the preceding embodiments of the first aspect of the invention, the first transport material has a hole mobility of5*10 - 4 cm 2 (vs) second transport material having a hole mobility of 5 to 10 -5 cm 2 /vs。
According to any one of the embodiments of the first aspect of the present invention, the light emitting structure layer further includes:
a hole injection layer between the hole transport layer and the first electrode, the hole injection layer comprising a hole injection material and a second hole transport material,
wherein the second hole transport material comprises at least a third transport material and a fourth transport material, the third transport material has a highest occupied molecular orbital level that is greater than the highest occupied molecular orbital level of the fourth transport material, and the third transport material has a hole mobility that is greater than the hole mobility of the fourth transport material.
According to any of the preceding embodiments of the first aspect of the present invention, at least one of the third transport material and the fourth transport material has a hole mobility greater than or equal to the second predetermined hole mobility, and the hole mobility of the third transport material and the fourth transport material after mixing is greater than or equal to ninety percent of the second predetermined hole mobility.
According to any one of the preceding embodiments of the first aspect of the present invention, the second predetermined hole mobility is 10 -5 cm 2 /vs。
According to any one of the preceding embodiments of the first aspect of the present invention, the difference in the highest occupied molecular orbital energy levels of the third and fourth transport materials is less than or equal to 0.05eV.
According to any one of the preceding embodiments of the first aspect of the present invention, at least one of the third transport material and the fourth transport material has a highest occupied molecular orbital level of less than or equal to-5.1 eV.
According to any one of the preceding embodiments of the first aspect of the invention, the first hole transporting material is the same material as the second hole transporting material.
According to any one of the preceding embodiments of the first aspect of the present invention, the mixing ratio of the first transporting material and the second transporting material is the same as the mixing ratio of the third transporting material and the fourth transporting material.
According to any one of the preceding embodiments of the first aspect of the present invention, the third transport material and the fourth transport material are mixed in a ratio of 0.4 to 2.4.
According to any one of the preceding embodiments of the first aspect of the present invention, the third and fourth transport materials are mixed in a ratio of 1:1.
According to any one of the preceding embodiments of the first aspect of the present invention, the third transport material has a highest occupied molecular orbital level of-5.15 eV and the fourth transport material has a highest occupied molecular orbital level of-5.18 eV.
According to any one of the preceding embodiments of the first aspect of the present invention, the third transport material has a hole mobility of 5 x 10 - 4 cm 2 (vi) a fourth transport material having a hole mobility of 5 x 10 -5 cm 2 /vs。
According to any one of the preceding embodiments of the first aspect of the present invention, in the hole injection layer, the mixing ratio of the hole injection material and the second hole transport material is less than or equal to 1.
In the hole injection layer according to any of the preceding embodiments of the first aspect of the present invention, the difference between the energy level of the highest occupied molecular orbital of the third transport material and the energy level of the lowest unoccupied molecular orbital of the hole injection material is less than or equal to 0.2ev.
Embodiments of the second aspect of the present invention provide a display device, including the display panel of any one of the embodiments of the first aspect.
In the display panel of the embodiment of the invention, the display panel comprises the first electrode, the second electrode and the light emitting structure layer positioned between the first electrode and the second electrode, and the light emitting structure layer can emit light through the action of the first electrode and the second electrode. The light emitting structure layer comprises a hole transport layer capable of transporting holes under the action of the first electrode and the second electrode. The material of the hole transport layer includes a first hole transport material including at least a first transport material and a second transport material. The first transport material and the second transport material both have different Highest Occupied Molecular Orbital (HOMO) energy levels and different hole mobilities. The HOMO energy level of the first transmission material is larger than that of the second transmission material, the HOMO energy level of the second transmission material is deeper, and the second transmission material with the deeper HOMO energy level can prolong the service life of the display panel. The hole mobility of the first transmission material is greater than that of the second transmission material, namely, the hole mobility of the first transmission material in the first transmission material and the second transmission material is greater, and the first transmission material with the greater hole mobility can ensure that the display panel has a lower driving voltage and reduce the power consumption of the display panel. Therefore, the material of the hole transport layer of the display panel in the embodiment of the invention can improve the service life of the device of the display panel and reduce the power consumption of the display panel by mixing the first transport material and the second transport material.
Drawings
Other features, objects and advantages of the invention will become apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings in which like or similar reference characters refer to the same or similar parts.
Fig. 1 is a partial cross-sectional view of a display panel according to an embodiment of a first aspect of the present invention;
FIG. 2 is a blue light index-luminance graph of a blue light device measured according to example 1;
FIG. 3 is a graph of lifetime degradation of a blue light device measured according to example 1;
FIG. 4 is a graph of current density versus voltage for a blue light device measured in accordance with example 2;
FIG. 5 is a graph of lifetime decay of a blue-emitting device measured according to example 2;
fig. 6 is a graph showing the voltage drift of the blue device measured according to example 2.
Description of reference numerals:
10. a display panel;
100. a first electrode;
200. a light emitting structure layer; 210. a hole injection layer; 220. a hole transport layer; 230. an electron blocking layer; 240. a light emitting layer; 250. a hole blocking layer; 260. an electron transport layer; 270. an electron injection layer;
300. a second electrode;
400. a light extraction layer;
500. and (7) packaging the layer.
Detailed Description
Features and exemplary embodiments of various aspects of the present invention will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the present invention. In the drawings and the following description, at least some well-known structures and techniques have not been shown in detail in order to avoid unnecessarily obscuring the present invention; also, the dimensions of some of the structures may be exaggerated for clarity. Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
In the description of the present invention, it is to be noted that, unless otherwise specified, "a plurality" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," and the like, as used herein, refer to orientations or positional relationships and are used merely to facilitate description of the invention and to simplify the description, but do not indicate or imply that the device or element so referred to must be oriented, constructed, and operated in a particular orientation and therefore should not be construed as limiting the invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The directional terms appearing in the following description are intended to be illustrative in all directions, and are not intended to limit the specific construction of embodiments of the present invention. In the description of the present invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "mounted" and "connected" are to be interpreted broadly, e.g., as either a fixed connection, a removable connection, or an integral connection; can be directly connected or indirectly connected. The specific meaning of the above terms in the present invention can be understood as appropriate to those of ordinary skill in the art.
For better understanding of the present invention, the display panel and the display device according to the embodiment of the present invention are described in detail below with reference to fig. 1 to 6.
Fig. 1 is a partial cross-sectional view of a display panel 10 according to an embodiment of the present invention.
As shown in fig. 1, according to a display panel 10 provided by an embodiment of the first aspect of the present invention, the display panel 10 includes: a first electrode 100, a second electrode 300, and a light emitting structure layer 200 between the first electrode 100 and the second electrode 300, the light emitting structure layer 200 including: a light-emitting layer 240; and a hole transport layer 220 between the light emitting layer 240 and the first electrode 100, wherein the material of the hole transport layer 220 includes a first hole transport material, wherein the first hole transport material includes at least a first transport material and a second transport material, the highest occupied molecular orbital level of the first transport material is greater than the highest occupied molecular orbital level of the second transport material, and the hole mobility of the first transport material is greater than the hole mobility of the second transport material.
In the display panel 10 of the embodiment of the invention, the display panel 10 includes the first electrode 100, the second electrode 300 and the light emitting structure layer 200 located between the first electrode 100 and the second electrode 300, and the light emitting structure layer 200 can emit light by the action of the first electrode 100 and the second electrode 300. The light emitting structure layer 200 includes a hole transport layer 220, and the hole transport layer 220 is capable of transporting holes by the first electrode 100 and the second electrode 300.
Herein, a Highest Occupied Molecular Orbital (HOMO) level of the organic material is a magnitude with respect to a vacuum level, and a value of the HOMO level is a negative number. The comparison of the HOMO energy levels in the present invention refers to the HOMO energy level value of the organic material, not the absolute value. For example, if the HOMO level of material A is-5.0 eV and the HOMO level of material B is-5.5 eV, then the HOMO level of material A is greater than the HOMO level of material B. Therefore, when the HOMO level of the hole transport material is deep, the HOMO level value of the material is low, and when the HOMO level of the hole transport material is shallow, the HOMO level of the material is high. That is, when the HOMO energy level of one hole transport material is greater than that of another hole transport material, the HOMO energy level of the one hole transport material is shallower than that of the other hole transport material.
The inventors found that a deeper Highest Occupied Molecular Orbital (HOMO) energy level of the hole transport material is beneficial to prolonging the service life of the device, while a faster hole mobility of the hole transport material is beneficial to reducing the voltage, and the hole transport material with a faster hole mobility is matched with an electron transport material with a higher electron mobility to obtain higher efficiency.
The material of the hole transport layer 220 includes a first hole transport material including at least a first transport material and a second transport material. The first transport material and the second transport material have different HOMO levels and different hole mobilities. The HOMO level of the first transport material is greater than the HOMO level of the second transport material, the HOMO level of the second transport material is deeper, and the deeper HOMO level of the second transport material can improve the device lifetime of the display panel 10. The hole mobility of the first transport material is greater than the hole mobility of the second transport material, that is, the hole mobility of the first transport material is greater, and the first transport material with the greater hole mobility can ensure that the display panel 10 has a lower driving voltage, thereby reducing the power consumption of the display panel 10. Therefore, in the embodiment of the present invention, the hole transport layer 220 of the display panel 10 is made of the first transport material and the second transport material, so that the lifetime of the display panel 10 can be prolonged, the power consumption of the display panel 10 can be reduced, and the display panel 10 has the characteristics of long lifetime and low power consumption.
In other embodiments, the first hole transporting material may further include a transporting material other than the first transporting material and the second transporting material, that is, the first hole transporting material may be formed by mixing three or more transporting materials.
Optionally, at least one of the first transport material and the second transport material has a HOMO level less than or equal to-5.1 eV. The hole transport layer 220 can be ensured to have a deeper HOMO level, and the hole transport layer 220 can be ensured to have a longer life.
The inventors have also found that when the difference in HOMO energy levels of the two transport materials is large, hole traps result. That is, when the difference in HOMO energy levels of the first transport material and the second transport material is large, a hole trap is caused. Holes are concentrated in a material with a deep HOMO level and are difficult to migrate, and the mobility of holes is high in a material with a shallow HOMO level, so that the number of holes in the material with the shallow HOMO level is small, and a hole trap occurs.
In the display panel 10 provided by the embodiment of the present invention, the difference between the highest occupied molecular orbital levels of the first transport material and the second transport material of the hole transport layer 220 is less than or equal to 0.05eV, which can improve hole traps caused by a large difference between HOMO levels of two or more hole transport materials.
In some alternative embodiments, at least one of the first transport material and the second transport material has a hole mobility greater than or equal to a first predetermined hole mobility, and the hole mobility of the first transport material and the second transport material after mixing is greater than or equal to ninety percent of the first predetermined hole mobility. It is possible to improve that the power consumption of the display panel 10 is too high due to too low hole mobility of the hole transport layer 220 after the first transport material and the second transport material are mixed. The first predetermined hole mobility is, for example, 10 -5 cm 2 Vs to ensure that the display panel 10 has a low power consumption.
Optionally, the mixing ratio of the first transmission material and the second transmission material is 0.4-2.4, for example, the mixing ratio of the first transmission material and the second transmission material is 3/7-7/3. For example, the mixing ratio of the first transporting material and the second transporting material is 3:7, 4:6, 5:5, 6:4, 7:3, or the like.
In these alternative embodiments, when the mixing ratio of the first transmission material and the second transmission material is within the above range, it is possible to avoid that the mixing ratio of the second transmission material is too high, which results in a higher voltage required to reach the target brightness, and the power consumption of the display panel 10 is increased. It is also possible to improve that the life of the display panel 10 is too low due to too high a mixing ratio of the first transfer material.
In some alternative embodiments, the mixing ratio of the first transport material and the second transport material is 1:1, i.e., the first transport material and the second transport material are mixed in equal proportion and prepared to form the hole transport layer 220, so that the hole transport layer 220 can achieve a long lifetime, low power consumption and high luminous efficiency.
The first transport material may be disposed in various ways, for example, the first transport material has a HOMO level of-5.15 eV and a hole mobility of 5 × 10 -4 cm 2 /vs。
The second transport material may be arranged in various ways, for example, the second transport material has a HOMO level of-5.18 eV and a hole mobility of 5 × 10 -5 cm 2 /vs。
In some optional embodiments, the light emitting structure layer 200 further includes a hole injection layer 210, the hole injection layer 210 is located between the hole transport layer 220 and the first electrode 100, the material of the hole injection layer 210 includes a hole injection material and a second hole transport material, wherein the second hole transport material includes at least a third transport material and a fourth transport material, the highest occupied molecular orbital energy level of the third transport material is greater than the highest occupied molecular orbital energy level of the fourth transport material, and the hole mobility of the third transport material is greater than the hole mobility of the fourth transport material.
In these alternative embodiments, the materials of the hole injection layer 210 include a hole injection material for generating holes and a second hole transport material for transporting holes.
The second hole transport material includes at least a third transport material and a fourth transport material. The third transport material and the fourth transport material have different HOMO levels and different hole mobilities. The HOMO level of the third transport material is greater than the HOMO level of the fourth transport material, the HOMO level of the fourth transport material is deeper, and the fourth transport material with the deeper HOMO level can improve the device lifetime of the display panel 10. The hole mobility of the third transport material is greater than the hole mobility of the fourth transport material, that is, the hole mobility of the third transport material is greater, and the third transport material with the greater hole mobility can ensure that the display panel 10 has a lower driving voltage, thereby reducing the power consumption of the display panel 10. Therefore, in the embodiment of the present invention, the material of the hole injection layer 210 of the display panel 10 is mixed with the third transport material and the fourth transport material, so that the device lifetime of the display panel 10 can be improved, the power consumption of the display panel 10 can be reduced, and the display panel 10 has the characteristics of long lifetime and low power consumption.
Optionally, the light emitting structure layer 200 may further include an electron blocking layer 230, the electron blocking layer 230 is located between the hole transport layer 220 and the light emitting layer 240, and the electron blocking layer 230 can block electrons of the light emitting layer 240 from flowing to the hole transport layer 220, so as to improve light emitting efficiency.
Optionally, the light emitting structure layer 200 further includes an electron injection layer 270 and an electron transport layer 260, the electron injection layer 270 is located between the light emitting layer 240 and the second electrode 300, and the electron transport layer 260 is located between the electron injection layer 270 and the light emitting layer 240. The light emitting structure layer 200 may further include a hole blocking layer 250, the hole blocking layer 250 being between the electron transport layer 260 and the light emitting layer 240, the hole blocking layer 250 for blocking holes from flowing to the electron transport layer 260. Optionally, the display panel 10 further includes, for example, a light extraction layer 400 and an encapsulation layer 500 disposed on a side of the second electrode 300 away from the light emitting structure layer 200.
One of the first and second electrodes 100 and 300 is an anode and the other is a cathode, and when the first and second electrodes 100 and 300 are turned on, the light emitting structure layer 200 can be excited to emit light. Optionally, the first electrode 100 is an anode and the second electrode 300 is a cathode. In the display panel 10, the first electrode 100 may also be a pixel electrode, the display panel 10 includes a plurality of first electrodes 100 distributed in an array, and the second electrode 300 may be a common electrode.
In some alternative embodiments, at least one of the third transport material and the fourth transport material has a hole mobility greater than or equal to a second predetermined hole mobility, and the hole mobility of the third transport material and the fourth transport material when combined is greater than or equal to ninety percent of the second predetermined hole mobility. It is possible to improve that the power consumption of the display panel 10 is too high due to too low hole mobility of the hole transport layer 220 after the third transport material and the fourth transport material are mixed. Second preset air gapHole mobility is, for example, 10 -5 cm 2 Vs to ensure that the display panel 10 has a low power consumption.
In the display panel 10 provided in the embodiment of the present invention, the difference between the highest occupied molecular orbital levels of the third transport material and the fourth transport material of the hole injection layer 210 is less than or equal to 0.05eV, which can improve hole traps caused by a large difference between the HOMO levels of the third transport material and the fourth transport material.
Optionally, at least one of the third transport material and the fourth transport material has a HOMO level less than or equal to-5.1 eV. The hole injection layer 210 can be ensured to have a deeper HOMO level, and the hole injection layer 210 can be ensured to have a longer lifetime.
The material of the hole injection layer 210 includes both the hole injection material and the second hole transport material, and the ratio of the hole injection material to the second hole transport material may be set in various ways. Optionally, the proportion of the hole injection material is less than or equal to 5%. The hole injection layer 210 has a better hole mobility, and crosstalk of the display panel 10 due to too high hole mobility of the hole injection layer 210 is avoided.
In some alternative embodiments, the mixing ratio of the hole injection material and the second hole transport material in the hole injection layer 210 is less than or equal to 1. The hole injection layer 210 has better hole mobility, and crosstalk of the display panel 10 caused by too high hole mobility of the hole injection layer 210 is avoided.
Optionally, the hole injecting material has a Lowest Unoccupied Molecular Orbital (LUMO) energy level, and a difference between the HOMO energy level of the third transport material and the LUMO energy level of the hole injecting material is less than or equal to 0.2ev. The difference between the HOMO level of the higher one of the third transport material and the fourth transport material and the LUMO level of the hole injection material is less than or equal to 0.2ev, and the HOMO level of the hole injection layer 210 is brought close to the LUMO level, so that the hole injection layer 210 has higher hole mobility.
The second hole transport material and the first hole transport material may be disposed in the same manner or in different manners. For example, the first hole transport material in the hole transport layer 220 is the same as the second hole transport material in the hole injection layer 210, so that the manufacturing process of the light emitting structure layer 200 can be simplified.
Alternatively, the mixing ratio of the first transport material and the second transport material in the hole transport layer 220 is the same as the mixing ratio of the third transport material and the fourth transport material in the hole injection layer 210.
In these alternative embodiments, the first hole transport material in the hole transport layer 220 and the second hole transport material in the hole injection layer 210 are the same in material type and in the same mixing ratio. Therefore, a hole transport material may be prepared in advance before the light emitting structure layer 200 is prepared, and then the hole transport material and the hole injection material are mixed to prepare the hole injection layer 210, and the hole transport material is directly used to prepare the hole transport layer 220, so that the preparation process of the light emitting structure layer 200 can be further simplified.
Optionally, the mixing ratio of the third transmission material and the fourth transmission material is 0.4-2.4. For example, the mixing ratio of the third transporting material and the fourth transporting material is 3:7, 4:6, 5:5, 6:4, 7:3, or the like.
In these alternative embodiments, when the mixing ratio of the third transmission material and the fourth transmission material is within the above range, it can be avoided that the mixing ratio of the fourth transmission material is too high, which results in a higher voltage required to reach the target brightness, and the power consumption of the display panel 10 is increased. It is also possible to improve that the life of the display panel 10 is too low due to too high a mixing ratio of the third transfer material.
In some optional embodiments, the mixing ratio of the third transport material and the fourth transport material is 1:1, that is, after the third transport material and the fourth transport material are mixed in equal proportion, a proper amount of hole injection material is added to prepare and form the hole injection layer 210, so that the hole injection layer 210 can have a long lifetime, low power consumption and high light emitting efficiency.
The third transport material may be disposed in various ways, for example, the third transport material has a HOMO energy level of-5.15 eV, and the third transport material has a high energy densityHole mobility of the material is 5 x 10 -4 cm 2 /vs。
The fourth transport material may be disposed in various ways, for example, the HOMO level of the fourth transport material is-5.18 eV, and the hole mobility of the fourth transport material is 5 × 10 -5 cm 2 /vs。
Optionally, the first transport material and the third transport material are the same material, and the second transport material and the fourth transport material are the same material, so that the hole injection layer 210 and the hole transport layer 220 may be made of the same hole transport material.
Optionally, the mixing ratio of the first transmission material and the second transmission material is equal to the mixing ratio of the third transmission material and the fourth transmission material. Namely, the hole injection layer 210 and the hole transport layer 220 are made of hole transport materials with the same material and the same proportion.
Alternatively, in the hole transport layer 220, the plurality of transport materials in the first hole transport material should be sufficiently mixed to be uniform to prepare the hole transport layer 220. For example, when the first hole transport material includes the first transport material and the second transport material, the first transport material and the second transport material are sufficiently mixed to be uniform to prepare the hole transport layer 220.
Alternatively, in the hole injection layer 210, the plurality of transport materials in the second hole transport material should be mixed well and mixed well with the hole injection material to prepare the hole injection layer 210. For example, when the second hole transport material includes a third transport material and a fourth transport material, the third transport material and the fourth transport material are sufficiently mixed with the hole injection material to prepare the hole injection layer 210.
Embodiments of the second aspect of the present invention further provide a display device, including the display panel of any one of the embodiments of the first aspect. Since the display device of the embodiment of the invention includes the display panel, the display device of the embodiment of the invention has the beneficial effects of the display panel, and the description is omitted here.
The display device in the embodiment of the present invention includes, but is not limited to, a mobile phone, a Personal Digital Assistant (PDA), a tablet pc, an electronic book, a television, a door lock, a smart phone, a console, and other devices having a display function.
To further illustrate the beneficial effects of the embodiments of the present invention, the following are specifically exemplified:
example 1
Specifically, the first electrode 100 is made of ITO, the hole injection layer 210 is made of two hole transport materials and one hole injection material, the hole transport layer 220 is made of two hole transport materials, and the electron blocking layer 230, the light emitting layer 240, the hole blocking layer 250, the electron transport layer 260, the electron injection layer 270 and the second electrode 300 are sequentially made on the hole transport layer 220. The two hole transport materials in the hole injection layer 210 and the hole transport layer 220 are the same in type and ratio.
The hole injection layer 210 is prepared by selecting a first material HT1 and a hole injection material, the hole transport layer 220 is prepared by selecting the first material HT1 as a comparative example 1, the hole injection layer 210 is prepared by mixing the first material HT1 and a second material HT2 in equal proportion and preparing the hole injection layer with one hole injection material, the hole transport layer 220 is prepared by mixing the first material HT1 and the second material HT2 in equal proportion and preparing the comparative example 2, the hole transport layer 210 is prepared by mixing the first material HT1 and a third material HT3 in equal proportion and preparing the hole transport layer 220 with one hole injection material, the hole transport layer 220 is prepared by mixing the first material HT1 and a third material HT3 in equal proportion and preparing the hole transport layer 210, the hole transport layer 220 is prepared by mixing the first material HT1 and a fourth material HT4 in equal proportion and preparing the hole transport layer 220 by mixing the first material HT1 and the fourth material HT4 in equal proportion and preparing the comparative example 4.
The HOMO energy level of the first material HT1 is greater than that of the second material HT2, the HOMO energy level of the second material HT2 is greater than that of the third material HT3, and the HOMO energy level of the third material HT3 is greater than that of the fourth material HT 4. The difference between the HOMO energy level of the first material HT1 and the HOMO energy level of the second material HT2 is less than 0.05ev, and the difference between the HOMO energy level of the first material HT1 and the HOMO energy level of the third material HT3 is more than 0.05evev, the difference between the HOMO energy level of the first material HT1 and the HOMO energy level of the fourth material HT4 is greater than 0.05ev. And the difference of the HOMO energy levels of the first material HT1 and the third material HT3 is smaller than that of the first material HT1 and the fourth material HT 4. The hole mobility of the first material HT1 is greater than the hole mobility of the second material HT2, the hole mobility of the second material HT2 is greater than the hole mobility of the third material HT3, and the hole mobility of the third material HT3 is greater than the hole mobility of the fourth material HT 4. The first material HT1 has a hole mobility of greater than 10 -5 cm 2 /vs。
The data of parameters such as current, voltage and brightness of the display panel 10 with the luminance of 1200nit are obtained as follows:
material Voltage (V) Current (mA) Current efficiency (cd/A) CIE-x CIE-y BI(cd/A/y)
HT1 4.07 1.443 7.49 0.141 0.041 184.50
HT1:HT2 4.09 1.269 8.52 0.138 0.046 186.63
HT1:HT3 4.18 1.490 7.25 0.141 0.041 175.08
HT1:HT4 4.84 1.262 8.56 0.137 0.048 179.73
The voltage is a voltage required to reach the target brightness, and the current is a current when the target brightness is reached. CIE-x and CIE-y are the color coordinates of the emitted subpixel colors, and BI is the blue light index.
Referring to fig. 2, fig. 2 is a graph of blue light index-luminance measured by the blue light device according to example 1.
As can be seen from comparison of comparative example 1 and comparative example 2, when a second material HT2, which is closer to both hole mobility and HOMO level thereof, is mixed in a first material HT1, the current slightly decreases, but the current efficiency significantly increases, and the voltages of comparative example 1 and comparative example 2 are close to the BI index. Comparative example 2 did not significantly deteriorate in voltage and BI values, and luminous efficiency, compared to comparative example 1.
As can be seen by continuing comparison between comparative example 2 and comparative example 3, after the third material HT3 having a large difference in hole mobility and HOMO level thereof was mixed in the first material HT1, the voltage rise was significant and the current efficiency was significantly decreased. As can be seen by continuing comparison of comparative example 2 and comparative example 4, after a fourth material HT4 having a large difference in hole mobility and HOMO level thereof was mixed in the first material HT1, the voltage was increased by 4.84V and the current was decreased to 1.262mA. The reason is that the first material HT1, the third material HT3, and the fourth material HT4 have large differences in hole mobility and HOMO level, and a hole trap occurs after mixing, so that the hole mobility of the hole injection layer 210 and the hole transport layer 220 after mixing is too low, which increases the voltage and reduces the efficiency.
Therefore, when an equal proportion of deep HOMO level material is mixed in the high hole mobility material, the hole mobility of the display panel 10 decreases, and the magnitude of the decrease is inversely proportional to the depth of the HOMO level of the added material, indicating that the HOMO level of the mixed material cannot be too deep.
In the embodiment of the present invention, the highest occupied molecular orbital energy levels of the first transport material and the second transport material in the hole transport layer 200 are different, and the difference between the highest occupied molecular orbital energy levels is less than or equal to 0.05eV, which can improve the problem of hole traps. Therefore, when the hole transport materials in the hole transport layer 220 and the hole injection layer 210 are prepared using a mixed material, the difference in HOMO energy level between the mixed materials cannot be too large.
Referring to fig. 3, fig. 3 illustrates a life decay graph of a blue device measured according to example 1 in comparative example 1 and comparative example 2. As can be seen from fig. 3, the lifetime of comparative example 2 is significantly higher than that of comparative example 1, and thus when the second material HT2 is mixed in the pure first material HT1, the device lifetime can be significantly provided without having a great influence on the light emitting efficiency and voltage of the device.
Example 2
Specifically, ITO is selected to prepare the first electrode 100, two hole transport materials and one hole injection material are selected to prepare the hole injection layer 210, two hole transport materials are selected to prepare the hole transport layer 220, and the electron blocking layer 230, the light emitting layer 240, the hole blocking layer 250, the electron transport layer 260, the electron injection layer 270 and the second electrode 300 are prepared on the hole transport layer 220. The two hole transport materials in the hole injection layer 210 and the hole transport layer 220 are the same in type and ratio.
The first material HT1 and the second material HT2 are mixed in different proportions to prepare the hole injection layer 210 and the hole transport layer 220, and the hole injection layer 210 is further doped with a hole injection material, so as to obtain data of parameters such as current, voltage, and luminance of the display panel 10 with the luminance of 1200nit as follows:
Figure BDA0003126016290000141
Figure BDA0003126016290000151
the former is the first material HT1 and the latter is the second material HT2. For example, when the material ratio is 1:0, the first material HT1 has a ratio of 1 and the second material HT2 has a ratio of 0 in the hole injection layer 210.
It is understood that there is a deviation in data obtained from the hole transport layer 220 and the hole injection layer 210 prepared in the same ratio of the same materials as in example 2 in example 1 due to the difference in measurement environment and time, and the deviation falls within the experimental error range.
From the above table, it can be seen that the voltage value and the BI value of the blue device are close when the mixing ratio of the first material HT1 and the second material HT2 is between 3:7 and 7:3, indicating that the efficiency process window is wide. The mixing ratio of the first material HT1 and the second material HT2 is between 3:7 and 7:3, which is similar to the voltage value and BI value of the pure first material HT1 and is higher than the voltage BI value of the pure second material HT2.
Referring to fig. 4, fig. 4 is a graph illustrating a current density-voltage curve of the blue light device according to example 2.
As shown in fig. 4, when the mixing ratio of the first material HT1 and the second material HT2 is between 3:7 and 7:3, the driving voltage of the blue device has a limited rise compared to the pure first material HT1, but a significant drop compared to the pure second material HT2. That is, when the mixing ratio of the first material HT1 and the second material HT2 is between 3:7 and 7:3, the voltage of the pure second material HT2 is small.
Referring to fig. 5, fig. 5 is a graph illustrating lifetime degradation of a blue light device measured according to example 2.
As shown in figure 5 of the drawings,
the life is increased when the mixing ratio of the second material HT2 is increased, and the life is saturated and approaches the life when the second material HT2 is pure when the mixing ratio of the second material HT2 exceeds 50%. The lifetime process window is wide, and the lifetime of the device when the second material HT2 is doped is obviously longer than that of the device when the first material HT1 is pure.
As can be understood from fig. 4 and 5, when the mixing ratio of the first material HT1 and the second material HT2 is between 3:7 and 7:3, the driving voltage of the display panel 10 is small and the lifetime is increased. When the mixing ratio of the first material HT1 and the second material HT2 is between 3:7 and 7:3, it is possible to improve the device lifetime of the display panel 10 and to reduce the power consumption of the display panel 10.
In addition, referring to fig. 6, fig. 6 is a graph illustrating a voltage drift curve of the blue device measured according to example 2. As shown in fig. 6, when the first material HT1 and the second material HT2 are doped, the voltage drift of the blue device is lower than that of the pure first material HT1 and the pure second material HT2.
In the embodiment of the present invention, the hole injection layer 210 and/or the hole transport layer 220 are/is prepared by doping more than two hole transport materials, which not only retains the low voltage characteristic of the high mobility material, but also retains the feature that the high HOMO energy level material prolongs the lifetime of the device, and has an effective effect on reducing the voltage drift of the device.
Further, as can be seen from the above embodiment 2, when the mixing ratio of the first transport material and the second transport material in the hole transport layer 220 is between 3/7 and 7/3, or the mixing ratio of the third transport material and the fourth transport material in the hole injection layer 210 is between 3/7 and 7/3, it is possible to achieve a balance between the lifetime, voltage, and efficiency, to extend the lifetime of the display panel 10, and to reduce the power consumption of the display panel 10.
While the application has been described with reference to a preferred embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the application. In particular, the technical features mentioned in the embodiments can be combined in any way as long as there is no structural conflict. The present application is not intended to be limited to the particular embodiments disclosed herein but is to cover all embodiments that may fall within the scope of the appended claims.

Claims (20)

1. A display panel, comprising: the light emitting diode device comprises a first electrode, a second electrode and a light emitting structure layer positioned between the first electrode and the second electrode, wherein the light emitting structure layer comprises:
a light emitting layer;
a hole transport layer between the light emitting layer and the first electrode, a material of the hole transport layer including a first hole transport material,
wherein the first hole transporting material comprises at least a first transporting material and a second transporting material, the first transporting material has a highest occupied molecular orbital level that is greater than a highest occupied molecular orbital level of the second transporting material, and the first transporting material has a hole mobility that is greater than a hole mobility of the second transporting material;
a hole injection layer between the hole transport layer and the first electrode, the hole injection layer being made of a material including a hole injection material and a second hole transport material,
wherein the second hole transport material comprises at least a third transport material and a fourth transport material, the third transport material has a highest occupied molecular orbital level that is greater than a highest occupied molecular orbital level of the fourth transport material, and the third transport material has a hole mobility that is greater than a hole mobility of the fourth transport material.
2. The display panel according to claim 1, wherein at least one of the first transport material and the second transport material has a hole mobility greater than or equal to a first predetermined hole mobility, and wherein the hole mobility of the mixed first transport material and second transport material is greater than or equal to ninety percent of the first predetermined hole mobility.
3. The display panel according to claim 2, wherein the first predetermined hole mobility is 10 -5 cm 2 /vs。
4. The display panel of claim 2 wherein the difference in the highest occupied molecular orbital energy levels of the first transport material and the second transport material is less than or equal to 0.05eV.
5. The display panel of claim 2, wherein at least one of the first transport material and the second transport material has a highest occupied molecular orbital level of less than or equal to-5.1 eV.
6. The display panel according to claim 1, wherein a mixing ratio value of the first transport material and the second transport material is 0.4 to 2.4.
7. The display panel according to claim 1, wherein a mixing ratio of the first transport material and the second transport material is 1:1.
8. The display panel according to claim 6,
the highest occupied molecular orbital level of the first transport material is-5.15 eV, and the highest occupied molecular orbital level of the second transport material is-5.18 eV;
and/or the first transport material has a hole mobility of 5 x 10 -4 cm 2 (vi) the second transport material has a hole mobility of 5 x 10 -5 cm 2 /vs。
9. The display panel according to claim 1, wherein at least one of the third and fourth transport materials has a hole mobility greater than or equal to a second predetermined hole mobility, and wherein the hole mobility of the third and fourth transport materials when mixed is greater than or equal to ninety percent of the second predetermined hole mobility.
10. The display panel according to claim 9, wherein the second predetermined hole mobility is 10 -5 cm 2 /vs。
11. The display panel of claim 9 wherein the difference in the highest occupied molecular orbital energy levels of the third and fourth transport materials is less than or equal to 0.05eV.
12. The display panel of claim 9 wherein at least one of the third transport material and the fourth transport material has a highest occupied molecular orbital level of less than or equal to-5.1 eV.
13. The display panel according to claim 1, wherein the first hole transport material is the same as a material of the second hole transport material.
14. The display panel according to claim 1, wherein a mixing ratio of the first transport material and the second transport material is the same as a mixing ratio of the third transport material and the fourth transport material.
15. The display panel according to claim 9,
the mixing ratio value of the third transmission material and the fourth transmission material is 0.4-2.4.
16. The display panel according to claim 9, wherein a mixing ratio of the third transfer material and the fourth transfer material is 1:1.
17. The display panel according to claim 15,
the third transport material has a highest occupied molecular orbital level of-5.15 eV, and the fourth transport material has a highest occupied molecular orbital level of-5.18 eV;
and/or the third transport material has a hole mobility of 5 x 10 -4 cm 2 (vi) the fourth transport material has a hole mobility of 5 x 10 -5 cm 2 /vs。
18. The display panel according to claim 9, wherein a mixing ratio of the hole injection material and the second hole transport material in the hole injection layer is 1.
19. The display panel according to claim 18, wherein in the hole injection layer, a difference between an energy level of a highest occupied molecular orbital of the third transport material and an energy level of a lowest unoccupied molecular orbital of the hole injection material is less than or equal to 0.2ev.
20. A display device characterized by comprising the display panel according to any one of claims 1 to 19.
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