CN109037467B - Electroluminescent device, display panel and display device - Google Patents
Electroluminescent device, display panel and display device Download PDFInfo
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- H—ELECTRICITY
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- 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
- H10K50/125—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers specially adapted for multicolour light emission, e.g. for emitting white light
- H10K50/13—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers specially adapted for multicolour light emission, e.g. for emitting white light comprising stacked EL layers within one EL unit
- H10K50/131—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers specially adapted for multicolour light emission, e.g. for emitting white light comprising stacked EL layers within one EL unit with spacer layers between the electroluminescent layers
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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]
- H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
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- 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
Abstract
The invention discloses an electroluminescent device, a display panel and a display device, wherein the electroluminescent device comprises: an anode layer, a cathode layer, a light emitting layer between the anode layer and the cathode layer; the light-emitting layer comprises at least two heterojunction light-emitting structures which are arranged in a stacked manner; the heterojunction light-emitting structure comprises a light-emitting material layer and a transmission material layer which are adjacently stacked, the carrier transmission characteristics of the light-emitting material layer and the transmission material layer are opposite, and the difference of the corresponding energy levels of the light-emitting material layer and the transmission material layer is not larger than a preset value. The light-emitting layer is at least provided with two heterojunction light-emitting structures which are arranged in a stacked mode, the light-emitting center is located at the interface of the heterojunction light-emitting structures, and the light-emitting areas can be formed in the light-emitting layer through the stacked arrangement of the heterojunction light-emitting structures, so that excitons are prevented from being excessively concentrated to generate quenching, and the light-emitting efficiency and the service life of the electroluminescent device are effectively improved.
Description
Technical Field
The invention relates to the technical field of packaging of electroluminescent display panels, in particular to an electroluminescent device, a display panel and a display device.
Background
Electroluminescent display panels, particularly display panels related to O L ED (Organic light Emitting Diode) devices, have become one of the key development directions of new generation flat panel display devices due to a series of excellent characteristics of self-luminescence, no need of backlight module, high contrast and definition, wide viewing angle, full curing, suitability for flexible panels, good temperature characteristics, low power consumption, fast response speed, low manufacturing cost, and the like, and thus have received more and more attention and are gradually put into mass production.
Currently, electroluminescent devices include an anode layer, a cathode layer, and a light-emitting layer disposed between the anode layer and the cathode layer, wherein the light-emitting layer is formed by proportionally incorporating a light-emitting guest into a suitable host material or materials, and has a single carrier transport property that results in a luminescent center at the interface of the light-emitting layer and the charge transport layer, such that local charge density and exciton density that are too high increase quenching of excitons, resulting in a reduced proportion of excitons that can be used for radiative transitions, resulting in lower device efficiency and shorter device lifetime.
Therefore, how to improve the luminous efficiency and lifetime of the electroluminescent device is a problem to be solved by those skilled in the art.
Disclosure of Invention
The invention aims to provide an electroluminescent device, a display panel and a display device, which are used for solving the problems of low luminous efficiency and short service life of the electroluminescent device in the prior art.
An embodiment of the present invention provides an electroluminescent device, including: an anode layer, a cathode layer, a light emitting layer between the anode layer and the cathode layer; the light-emitting layer comprises at least two heterojunction light-emitting structures which are arranged in a stacked manner;
the heterojunction light-emitting structure comprises a light-emitting material layer and a transmission material layer which are adjacently stacked, the carrier transmission characteristics of the light-emitting material layer and the transmission material layer are opposite, and the difference of the corresponding energy levels of the light-emitting material layer and the transmission material layer is not larger than a preset value.
In a possible implementation manner, in the above electroluminescent device provided by the embodiment of the present invention, the luminescent material layer includes an N-type luminescent material, and the transport material layer includes a P-type transport material.
In a possible implementation manner, in the above electroluminescent device provided by the embodiment of the present invention, the lowest energy level of the transport material layer is greater than the lowest energy level of the luminescent material layer, and the highest energy level of the transport material layer is less than the highest energy level of the luminescent material layer.
In a possible implementation manner, in the above electroluminescent device provided by the embodiment of the present invention, the luminescent material layer includes a P-type luminescent material, and the transport material layer includes an N-type transport material.
In a possible implementation manner, in the above electroluminescent device provided by the embodiment of the present invention, the lowest energy level of the luminescent material layer is greater than the lowest energy level of the transport material layer, and the highest energy level of the luminescent material layer is less than the highest energy level of the transport material layer.
In a possible implementation manner, in the electroluminescent device provided in the embodiment of the present invention, a value range of the preset value is greater than 0eV and less than or equal to 3 eV.
In a possible implementation manner, in the above electroluminescent device provided by the embodiment of the present invention, the thickness of the luminescent material layer is smaller than the thickness of the transmission material layer.
In a possible implementation manner, the embodiment of the invention provides the above electroluminescent device, wherein the thickness of the heterojunction light emitting structure is 1nm to 40 nm.
Correspondingly, the embodiment of the invention also provides a display panel comprising the electroluminescent device in any one of the embodiments.
Correspondingly, the embodiment of the invention also provides a display device which comprises the display panel in any embodiment.
The invention has the following beneficial effects:
the electroluminescent device, the display panel and the display device provided by the embodiment of the invention comprise: an anode layer, a cathode layer, a light emitting layer between the anode layer and the cathode layer; the light-emitting layer comprises at least two heterojunction light-emitting structures which are arranged in a stacked manner; the heterojunction light-emitting structure comprises a light-emitting material layer and a transmission material layer which are adjacently stacked, the carrier transmission characteristics of the light-emitting material layer and the transmission material layer are opposite, and the difference of the corresponding energy levels of the light-emitting material layer and the transmission material layer is not larger than a preset value. The light-emitting layer is at least provided with two heterojunction light-emitting structures which are arranged in a stacked mode, the light-emitting center is located at the interface of the heterojunction light-emitting structures, and the light-emitting areas can be formed in the light-emitting layer through the stacked arrangement of the heterojunction light-emitting structures, so that excitons are prevented from being excessively concentrated to generate quenching, and the light-emitting efficiency and the service life of the electroluminescent device are effectively improved.
Drawings
FIG. 1 is a schematic diagram of a prior art hierarchical structure of an electroluminescent device;
FIG. 2 is a schematic diagram of the energy level structure of the electroluminescent device shown in FIG. 1;
fig. 3 is a schematic diagram of a hierarchical structure of an electroluminescent device according to an embodiment of the present invention;
fig. 4 is one of schematic energy level structures of a heterojunction light emitting structure in an electroluminescent device provided by an embodiment of the present invention;
fig. 5 is a second schematic diagram illustrating an energy level structure of a heterojunction light emitting structure in an electroluminescent device according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of the energy level structure of an electroluminescent device incorporating the heterojunction light-emitting structure shown in FIG. 4;
FIG. 7 is a schematic diagram of the energy level structure of an electroluminescent device incorporating the heterojunction light-emitting structure shown in FIG. 5;
fig. 8 is a graph of current density versus voltage for an electroluminescent device provided in accordance with an embodiment of the present invention and a light-emitting device provided in accordance with the prior art;
fig. 9 is a graph of current density versus current efficiency for an electroluminescent device provided in accordance with an embodiment of the present invention as compared to a light-emitting device provided in accordance with the prior art;
FIG. 10 is a graph comparing the lifetime decay of an electroluminescent device provided by an embodiment of the present invention with that of a prior art light-emitting device at 50mA/cm 2.
Detailed Description
The related art electroluminescent device, as shown in fig. 1, includes an anode layer 10, a hole injection layer 11, a hole transport layer 12, a light emitting layer 13, an electron transport layer 14, an electron injection layer 15, and a cathode layer 16, wherein the light emitting layer 13 is formed by incorporating a light emitting guest into a suitable host material or host materials. As shown in fig. 2, since the light emitting layer has a single carrier transport property, the light emitting region is located at the interface between the light emitting layer and the charge transport layer (hole transport layer or electron transport layer), where fig. 2 is illustrated by taking the light emitting region as an example at the interface between the hole transport layer and the light emitting layer, resulting in an excessively large charge density and exciton density at the interface, thereby increasing the probability of exciton quenching, resulting in a reduced proportion of excitons that can be used for radiation transition, resulting in a lower efficiency and a shorter lifetime of the device. In addition, the light-emitting layer has only a single light-emitting center, and the thickness of the light-emitting layer is usually 20 to 40nm in consideration of both electrical and optical factors of the device, but an effective light-emitting region thereof is only in the range of 5 to 10nm extending from the interface toward the side of the light-emitting layer away from the interface, and thus the utilization rate of the light-emitting layer is low.
Therefore, in order to alleviate the problems of low luminous efficiency and short lifetime of the electroluminescent device in the related art, embodiments of the present invention provide an electroluminescent device, a display panel, and a display apparatus. In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The following describes in detail specific embodiments of an electroluminescent device, a display panel, and a display device according to embodiments of the present invention with reference to the accompanying drawings.
The thicknesses and shapes of the film layers in the drawings do not reflect actual proportions, and are merely intended to schematically illustrate the present invention.
An electroluminescent device provided in an embodiment of the present invention, as shown in fig. 3, includes: an anode layer 20, a cathode layer 26, and a light-emitting layer 23 located between the anode layer 20 and the cathode layer 26; the light-emitting layer 23 includes at least two heterojunction light-emitting structures 231 arranged in a stack;
the heterojunction light emitting structure 231 comprises a light emitting material layer 1 and a transmission material layer 2 which are adjacently stacked, the carrier transmission characteristics of the light emitting material layer 1 and the transmission material layer 2 are opposite, and the difference between the corresponding energy levels of the light emitting material layer 1 and the transmission material layer 2 is not greater than a preset value.
The electroluminescent device provided by the embodiment of the invention comprises: an anode layer, a cathode layer, a light emitting layer between the anode layer and the cathode layer; the light-emitting layer comprises at least two heterojunction light-emitting structures which are arranged in a stacked manner; the heterojunction light-emitting structure comprises a light-emitting material layer and a transmission material layer which are adjacently stacked, the carrier transmission characteristics of the light-emitting material layer and the transmission material layer are opposite, and the difference of the corresponding energy levels of the light-emitting material layer and the transmission material layer is not larger than a preset value. The light-emitting layer is at least provided with two heterojunction light-emitting structures which are arranged in a stacked mode, the light-emitting center is located at the interface of the heterojunction light-emitting structures, and the light-emitting areas can be formed in the light-emitting layer through the stacked arrangement of the heterojunction light-emitting structures, so that excitons are prevented from being excessively concentrated to generate quenching, and the light-emitting efficiency and the service life of the electroluminescent device are effectively improved.
Of course, as shown in fig. 3, the electroluminescent device further includes a hole injection layer 21 and a hole transport layer 22 between the anode layer 20 and the light emitting layer 23, and an electron injection layer 25 and an electron transport layer 24 between the cathode layer 26 and the light emitting layer 23. Wherein, the light emitting layer 23 comprises at least two heterojunction light emitting structures 231 arranged in a stacked manner, and the heterojunction light emitting structure 231 comprises a light emitting material layer 1 and a transmission material layer 2, wherein the carrier transmission characteristics of the light emitting material layer 1 and the transmission material layer 2 are opposite, namely in one layer, electrons are carriers, and in the other layer, holes are carriers, so as to form a heterojunction (p-n junction) light emitting structure; and the difference between the highest energy level or the lowest energy level of the materials selected for the luminescent material layer 1 and the transport material layer 2 needs to satisfy the requirement of a preset value to ensure that carriers are confined at the interface between the luminescent material layer 1 and the transport material layer 2 to form a luminescent center without being diffused to another layer. As can be seen from the above description, a light emitting region is formed at the interface between the light emitting material layer 1 and the transport material layer 2 in each of the heterojunction light emitting structures 231, and a plurality of heterojunction light emitting structures 231 are included in the light emitting layer 23, and each heterojunction light emitting structure 231 includes a light emitting region, so that a plurality of light emitting regions exist in the light emitting layer 23 of the electroluminescent device provided by the present invention, carriers are uniformly distributed in each light emitting region, rather than being concentrated at a certain interface, and the proportion of excitons for radiation transition is increased, so that the luminous efficiency and the lifetime of the electroluminescent device are increased.
It should be noted that fig. 3 illustrates an example of a heterojunction light emitting structure in which a light emitting layer includes 3 stacked layers, where how many heterojunction light emitting structures in which the light emitting layer includes are selected according to usage, and the more the heterojunction light emitting structures are disposed, the better the light emitting efficiency and the lifetime of the electroluminescent device will be, but the light emitting layer is relatively thick, so that various factors need to be comprehensively considered to determine the number of the light emitting layers including the heterojunction light emitting structures, and the number is not limited specifically here.
Alternatively, in the above electroluminescent device provided by the embodiment of the present invention, as shown in fig. 4 and 6, the luminescent material layer includes an N-type luminescent material, and the transport material layer includes a P-type transport material.
Specifically, in the electroluminescent device provided in the embodiment of the present invention, the light-emitting material layer is doped with an N-type light-emitting material, so that carriers of the light-emitting material are electrons; the transport material layer is doped with a P-type transport material, so that carriers of the transport material layer are holes, and a heterojunction (i.e., a P-n junction) is formed at the interface of the light emitting material layer and the transport material layer, so that a light emitting center is defined at the interface of the light emitting material layer and the transport material layer, and a light emitting region a is formed.
In the electroluminescent device provided in the embodiments of the present invention, the N-type light-emitting material is a light-emitting material with electrons as main carriers, and the P-type transport material is a transport material with holes as main carriers.
Optionally, in the above electroluminescent device provided by the embodiment of the present invention, the lowest energy level of the transport material layer is greater than the lowest energy level of the luminescent material layer, and the highest energy level of the transport material layer is less than the highest energy level of the luminescent material layer.
Specifically, in the above-described electroluminescent device provided by the embodiment of the present invention, in order to make the P-type carriers (holes) in the transport material layer unable to enter the light-emitting material layer through the interface between the transport material layer and the light-emitting material layer to combine with the N-type carriers (electrons) in the light-emitting material layer, it is necessary to make the lowest energy level (L umo level) of the transport material layer larger than the lowest energy level (L umo level) of the light-emitting material layer.
Alternatively, in the above electroluminescent device provided by the embodiment of the present invention, as shown in fig. 5 and 7, the luminescent material layer includes a P-type luminescent material, and the transport material layer includes an N-type transport material.
Specifically, in the electroluminescent device provided in the embodiment of the present invention, the light-emitting material layer is doped with a P-type light-emitting material, so that carriers of the light-emitting material are holes; the transmission material layer is doped with an N-type transmission material, so that carriers of the transmission material layer are electrons, thereby forming a heterojunction (i.e., a p-N junction) at the interface of the light emitting material layer and the transmission material layer, thereby defining a light emitting center at the interface of the light emitting material layer and the transmission material layer, and forming a light emitting region a.
In the electroluminescent device provided in the embodiments of the present invention, the P-type light-emitting material is a light-emitting material with holes as main carriers, and the N-type transport material is a transport material with electrons as main carriers.
Optionally, in the above electroluminescent device provided by the embodiment of the present invention, the lowest energy level of the luminescent material layer is greater than the lowest energy level of the transport material layer, and the highest energy level of the luminescent material layer is less than the highest energy level of the transport material layer.
Specifically, in the above-described electroluminescent device provided by the embodiment of the present invention, in order to make the P-type carriers (holes) in the light-emitting material layer not enter the transport material layer through the interface between the transport material layer and the light-emitting material layer and combine with the N-type carriers (electrons) in the transport material layer, it is necessary to make the lowest energy level (L umo level) of the light-emitting material layer larger than the lowest energy level (L umo level) of the transport material layer.
Optionally, in the electroluminescent device provided in the embodiment of the present invention, a value range of the preset value is greater than 0eV and less than or equal to 3 eV.
Specifically, in the above electroluminescent device provided by the embodiment of the present invention, when the difference between the highest energy level of the luminescent material layer and the highest energy level of the transport material layer is greater than 0eV and less than or equal to 3eV, the charge concentration at the adjacent interface of the luminescent material layer and the transport material layer is better, which is beneficial to increase the luminous efficiency and the lifetime of the electroluminescent device; similarly, when the difference between the lowest energy level of the light-emitting material layer and the lowest energy level of the transport material layer is greater than 0eV and less than or equal to 3eV, the charge concentration at the adjacent interface of the light-emitting material layer and the transport material layer is also better, which is beneficial to increasing the light-emitting efficiency and the lifetime of the electroluminescent device.
Optionally, in the above electroluminescent device provided in this embodiment of the present invention, a thickness of the luminescent material layer is smaller than a thickness of the transmission material layer.
Specifically, in the above electroluminescent device provided by the embodiment of the present invention, in the heterojunction light-emitting structure, the light-emitting region is only at a certain distance from the adjacent interface between the light-emitting material layer and the transmission material layer, generally at a position 5-10nm from the interface toward the extension direction of the light-emitting material layer, so that even if the thickness of the light-emitting material layer is made thicker, the effective area for light emission is only 5-10nm, and thus, the light-emitting requirement of the heterojunction light-emitting structure can be fully satisfied by setting the thickness of the light-emitting material layer to about 1-20nm, the thickness of the light-emitting layer can be effectively controlled, the usage of the light-emitting material can be reduced, and the production cost.
Optionally, in the above electroluminescent device provided by the embodiment of the present invention, the thickness of the heterojunction light emitting structure is 1nm to 40 nm.
Specifically, in the above electroluminescent device provided by the embodiment of the present invention, the thickness of the heterojunction light emitting structure is 1nm to 40nm, and the light emitting layer may be formed by multiple stacking of the heterojunction light emitting structure, wherein the thickness of the light emitting material layer may be maintained in a range of 1nm to 20nm, the thickness of the transmission material layer may also be maintained in a range of 1nm to 20nm, and the thickness of the light emitting layer only needs to meet the light emitting requirement of the heterojunction light emitting structure, and the thickness of the light emitting layer is maintained by adjusting the thickness of the transmission material layer.
Examples
Taking the example that the light emitting material layer comprises an N-type light emitting material and the transmission material layer comprises a P-type transmission material as an example, specifically, the light emitting material layer is an N-type blue thermally-excited delayed fluorescence light emitting material DMAC-DPS, the transmission material of the transmission material layer is CBP, the N-type light emitting material DMAC-DPS and the P-type transmission material form a heterojunction light emitting structure as shown in fig. 4, and the junctions of the heterojunction light emitting structure are repeatedly stacked three times to form a light emitting layer.
The electroluminescent device comprises an anode layer, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer and a cathode layer, wherein the anode layer is made of transparent ITO glass, the hole injection layer is made of PEDOT (Poly ethylene glycol terephthalate) (PSS) materials, the hole transport material m-MTDATA materials are used as electron donors in the hole transport layer and the light emitting layer, the electron transport material 3TPYMB materials are used as electron acceptors in the electron transport layer and the light emitting layer, the electron injection layer is made of L iF materials, and the cathode layer is made of Al metal materials.
The preparation process of the electroluminescent device comprises the steps of taking the transparent glass with the ITO as a substrate, forming an ITO pattern electrode through photoetching, sequentially cleaning the ITO glass substrate in an ultrasonic environment in deionized water, acetone and absolute ethyl alcohol, and then using N to prepare the transparent glass with the ITO pattern electrode2Blow-dry and perform O2Plasma processing to form an anode layer of the electroluminescent device; then, a hole injection layer (PEDOT: PSS) and a hole transport layer (m-MTDATA, with a hole mobility of 2 x 10) were formed on the anode layer-4cm2V-1s-1) (ii) a Sequentially forming a transmission material layer (CBP) and a light-emitting material layer (DMAC-DPS) on the side of the hole transmission layer away from the anode layer to form a heterojunction light-emitting structure, repeatedly stacking the heterojunction light-emitting structure for three times to form a light-emitting layer, and sequentially forming an electron transmission layer (3TPYMB with electron mobility of 1 x 10 on the light-emitting layer-5cm2V-1s-1) Wherein, all film materials except the anode layer are formed into films by thermal evaporation, the vacuum degree of the cavity is 3 × 10-6Torr during thermal evaporation, and the evaporation rate is maintained at
The film thickness was measured by XP-2 step meter. Removing yinThe light emitting area of the electroluminescent device formed by using a metal cathode mask (metal mask) for the electrode layer (Al) and an open mask (open mask) for the rest layers and an evaporation rate of 0.1nm/s is 2mm × 2mm, and the structure of the specifically formed electroluminescent device is as follows:
D1:ITO/PEDOT:PSS/m-MTDATA(30nm)/CBP(15nm)/DMAC-DPS(1nm)/CBP(5nm)/DMAC-DPS(1nm)/CBP(15nm)/DMAC-DPS(1nm)/3TPYMB(25nm)/LiF(1nm)/Al(100nm)。
in order to ensure the accuracy of the experimental result, the device is packaged. The encapsulation method adopted in the experiment is to cover the area to be encapsulated by using a glass cover plate, then coat ultraviolet curing glue on the periphery of the area, and irradiate the area for 20 to 25 minutes under an ultraviolet lamp with the wavelength of 265nm to form the encapsulated electroluminescent device.
Comparing the performances of the top electroluminescent device and the standard device in the prior art, as shown in fig. 8, 9 and 10, compared with the standard device in the prior art, the maximum current efficiency of the electroluminescent device provided by the above embodiment of the present invention is improved from 9cd/a to 14cd/a, and the improvement range is about 60%; the working voltage is reduced; the service life is obviously prolonged. Namely, by arranging the light emitting layer of the electroluminescent device into a plurality of heterojunction light emitting structures in a stacked mode, the starting voltage of the electroluminescent device is reduced, the efficiency is improved, and the light emitting performance, the stability and the like of the electroluminescent device are greatly improved.
Based on the same inventive concept, embodiments of the present invention further provide a display panel, including the electroluminescent device provided in any of the above embodiments.
Since the principle of the display panel to solve the problem is similar to that of the above electroluminescent device, the implementation of the display panel can be referred to the implementation of the above electroluminescent device, and repeated descriptions are omitted.
Based on the same inventive concept, the embodiment of the invention further provides a display device, which comprises any one of the display panels provided by the embodiment of the invention. Since the principle of the display device to solve the problem is similar to the aforementioned one, the display device may be: any product or component with a display function, such as a mobile phone, a tablet computer, a television, a display, a notebook computer, a digital photo frame, a navigator and the like. The implementation of the display device can be referred to the above embodiments of the organic light emitting display panel, and repeated descriptions are omitted.
The electroluminescent device, the display panel and the display device provided by the embodiment of the invention comprise: an anode layer, a cathode layer, a light emitting layer between the anode layer and the cathode layer; the light-emitting layer comprises at least two heterojunction light-emitting structures which are arranged in a stacked manner; the heterojunction light-emitting structure comprises a light-emitting material layer and a transmission material layer which are adjacently stacked, the carrier transmission characteristics of the light-emitting material layer and the transmission material layer are opposite, and the difference of the corresponding energy levels of the light-emitting material layer and the transmission material layer is not larger than a preset value. The light-emitting layer is at least provided with two heterojunction light-emitting structures which are arranged in a stacked mode, the light-emitting center is located at the interface of the heterojunction light-emitting structures, and the light-emitting areas can be formed in the light-emitting layer through the stacked arrangement of the heterojunction light-emitting structures, so that excitons are prevented from being excessively concentrated to generate quenching, and the light-emitting efficiency and the service life of the electroluminescent device are effectively improved.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (4)
1. An electroluminescent device comprising: an anode layer, a cathode layer, a light emitting layer between the anode layer and the cathode layer; the light-emitting layer comprises at least two heterojunction light-emitting structures which are arranged in a stacked manner;
the heterojunction light-emitting structure comprises a light-emitting material layer and a transmission material layer which are adjacently stacked, wherein the carrier transmission characteristics of the light-emitting material layer and the transmission material layer are opposite;
wherein when the light emitting material layer includes an N-type light emitting material, the transport material layer includes a P-type transport material, an L umo level of the transport material layer is greater than an L umo level of the light emitting material layer, an energy level difference between an L umo level of the transport material layer and a L umo level of the light emitting material layer is greater than 0eV and equal to or less than 3eV, a Homo level of the transport material layer is less than a Homo level of the light emitting material layer, and an energy level difference between the Homo level of the transport material layer and the Homo level of the light emitting material layer is greater than 0eV and equal to or less than 3 eV;
the light emitting material layer includes a P-type light emitting material, when the transport material layer includes an N-type transport material, an L umo level of the light emitting material layer is greater than a L umo level of the transport material layer, an energy level difference between a L umo level of the light emitting material layer and a L umo level of the transport material layer is greater than 0eV and equal to or less than 3eV, a Homo level of the light emitting material layer is less than a Homo level of the transport material layer, and an energy level difference between a Homo level of the light emitting material layer and a Homo level of the transport material layer is greater than 0eV and equal to or less than 3 eV;
the thickness of the luminescent material layer is smaller than that of the transmission material layer.
2. An electroluminescent device as claimed in claim 1, characterized in that the thickness of the heterojunction light-emitting structure is from 1nm to 40 nm.
3. A display panel comprising an electroluminescent device as claimed in claim 1 or 2.
4. A display device characterized by comprising the display panel according to claim 3.
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| CN100534246C (en) * | 2003-08-22 | 2009-08-26 | 索尼株式会社 | Organic e l device and display |
| JP2005129455A (en) * | 2003-10-27 | 2005-05-19 | Kansho Ho | Organic light emitting element |
| JP4276109B2 (en) * | 2004-03-01 | 2009-06-10 | ローム株式会社 | Organic electroluminescent device |
| US20060244373A1 (en) * | 2005-04-28 | 2006-11-02 | Semiconductor Energy Laboratory Co., Ltd. | Light emitting device and method for manufacturing thereof |
| CN101517759B (en) * | 2006-09-26 | 2012-07-04 | 昭和电工株式会社 | Method for manufacturing group iii nitride compound semiconductor light-emitting device, group iii nitride compound semiconductor light-emitting device, and lamp |
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