CN115312679A - Laminated electroluminescent device, display panel and display device - Google Patents

Abstract

The present disclosure relates to a stacked electroluminescent device, a display panel, and a display apparatus, the stacked electroluminescent device includes a first light emitting layer and a second light emitting layer, the first light emitting layer is far away from a light emitting side of the light emitting device, the second light emitting layer is close to the light emitting side of the light emitting device, a difference between a LUMO level of an electronic host material of the first light emitting layer and a HOMO level of a hole-type host material is a first energy level difference, a difference between a LUMO level of an electronic host material of the second light emitting layer and a HOMO level of the hole-type host material is a second energy level difference, and the first energy level difference is greater than the second energy level difference, so that a blue shift of light emitted by a carrier through Langevin recombination (Langevin recombination) can be overlapped with a spectrum of the light emitting device itself, a spectrum of the first light emitting layer is narrowed, a color purity of the first light emitting layer is improved, and a total color gamut of the stacked electroluminescent device can be improved, and coverage is improved.

Description

Laminated electroluminescent device, display panel and display device

Technical Field

The disclosure relates to the technical field of display, in particular to a laminated electroluminescent device, a display panel and a display device.

Background

Organic light-emitting diodes (OLEDs), as a new generation of light-emitting display technology behind liquid crystal display, have the advantages of wide visible angle, high contrast, bright color, flexible display, and the like, and have been widely applied to various mobile phones and wearable devices.

Organic light emitting diodes can generally have a high color gamut due to their self-luminous properties. To further increase the efficiency of the device, a stacked electroluminescent device may be used, however, the efficiency of the light emitting device is reduced, the spectrum is broadened and the color gamut is reduced due to the fact that the light emitting layer on the side far away from the light emitting side is generally subjected to larger loss.

It is to be noted that the information disclosed in the above background section is only for enhancement of understanding of the background of the present disclosure, and thus may include information that does not constitute prior art known to those of ordinary skill in the art.

Disclosure of Invention

The present disclosure is directed to solving the problems of reduced efficiency, broadened spectrum, and reduced color gamut of a light emitting device due to the larger loss generally faced by a light emitting layer far from the light emitting side, and provides a stacked electroluminescent device, a display panel, and a display apparatus.

According to an aspect of the present disclosure, there is provided a stacked electroluminescent device including a first electrode, a second electrode, a first light emitting layer, and a second light emitting layer, the first electrode being an opaque electrode; the second electrode is a transparent electrode or a semitransparent electrode; the first light-emitting layer is arranged between the first electrode and the second electrode; the second light-emitting layer is arranged between the first light-emitting layer and the second electrode; the first light-emitting layer and the second light-emitting layer both comprise an electron type host material, a hole type host material and a light-emitting doping material, the difference between the LUMO energy level of the electron type host material of the first light-emitting layer and the HOMO energy level of the hole type host material is a first energy level difference, the difference between the LUMO energy level of the electron type host material of the second light-emitting layer and the HOMO energy level of the hole type host material is a second energy level difference, and the first energy level difference is larger than the second energy level difference.

In one embodiment of the present disclosure, the difference between the plurality of first energy level differences and the second energy level difference is equal to or greater than 0.1eV.

In one embodiment of the present disclosure, the half-peak width of the emission spectrum of the first light emitting layer is 1 to 10nm narrower than the half-peak width of the emission spectrum of the second light emitting layer.

In one embodiment of the present disclosure, the half-width of the intrinsic spectrum or electroluminescence spectrum of the light emitting dopant material of the first light emitting layer is 1 to 10nm narrower than the half-width of the intrinsic spectrum or electroluminescence spectrum of the light emitting dopant material of the second light emitting layer.

In one embodiment of the present disclosure, the stacked electroluminescent device further includes a charge generation layer, a first hole transport layer, and a first electron transport layer, the charge generation layer being disposed between the first light emitting layer and the second light emitting layer; the first hole transport layer is arranged between the first electrode and the first light emitting layer; the first electron transport layer is arranged between the second light-emitting layer and the second electrode.

In one embodiment of the present disclosure, the stacked electroluminescent device further includes a second hole transport layer and a second electron transport layer, the second hole transport layer being disposed between the charge generation layer and the second light emitting layer; the second electron transport layer is disposed between the first light emitting layer and the charge generation layer.

In one embodiment of the present disclosure, the stacked electroluminescent device further comprises a hole injection layer and/or an electron injection layer, the hole injection layer being provided between the first electrode and the first hole transport layer; the electron injection layer is arranged between the first electron transport layer and the second electrode.

In one embodiment of the present disclosure, when the second electrode is a translucent electrode, the stacked electroluminescent device further includes a capping layer disposed on a side of the second electrode away from the first electrode.

In one embodiment of the present disclosure, the material of the second electrode is a transparent metal oxide, a simple metal, or a metal alloy.

In one embodiment of the present disclosure, the first electrode includes a metal layer, and a material of the metal layer is silver, aluminum, magnesium, calcium, a silver alloy, an aluminum alloy, a magnesium alloy, or a calcium alloy.

In one embodiment of the present disclosure, the first electrode further includes a transparent metal oxide layer disposed on opposite sides of the metal layer.

In one embodiment of the present disclosure, the charge generation layer includes an n-type doped organic layer and an inorganic metal oxide, or the charge generation layer includes an n-type doped organic layer and a single organic layer.

According to another aspect of the present disclosure, there is provided a display panel including an array substrate and a light emitting layer group, the light emitting layer group being disposed at one side of the array substrate, the light emitting layer group including the stacked electroluminescent device according to one aspect of the present disclosure.

According to still another aspect of the present disclosure, there is provided a display device including the display panel according to another aspect of the present disclosure.

The laminated electroluminescent device comprises a first light-emitting layer and a second light-emitting layer, wherein the first light-emitting layer is far away from the light-emitting side of the light-emitting device, the second light-emitting layer is close to the light-emitting side of the light-emitting device, the difference value between the LUMO energy level of an electronic type main body material of the first light-emitting layer and the HOMO energy level of a hole type main body material is a first energy level difference, the difference value between the LUMO energy level of an electronic type main body material of the second light-emitting layer and the HOMO energy level of the hole type main body material is a second energy level difference, the first energy level difference is larger than the second energy level difference, light emitted by carriers through Langevin recombination (Langevin recombination) can be blue-shifted and overlapped with the spectrum of the light-emitting device, the spectrum of the first light-emitting layer is narrowed, the color purity of the first light-emitting layer is improved, the total color purity of the laminated electroluminescent device can be improved, and the color gamut coverage is improved.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and together with the description, serve to explain the principles of the disclosure. It should be apparent that the drawings in the following description are merely examples of the disclosure and that other drawings may be derived by those of ordinary skill in the art without inventive effort.

Fig. 1 is a schematic cross-sectional view of a stacked electroluminescent device according to an embodiment of the present disclosure.

Fig. 2 is a schematic cross-sectional view of another stacked electroluminescent device according to an embodiment of the present disclosure.

Fig. 3 is a schematic cross-sectional view of yet another stacked electroluminescent device according to an embodiment of the present disclosure.

Fig. 4 is a schematic cross-sectional view of yet another stacked electroluminescent device according to an embodiment of the present disclosure.

Fig. 5 is a schematic cross-sectional view of another stacked electroluminescent device according to embodiments of the present disclosure.

Fig. 6 shows electroluminescence spectra of different light emitting layers of a stacked electroluminescent device according to an embodiment of the present disclosure.

Fig. 7 is a schematic diagram when the difference between the LUMO level of the electron-type host material and the HOMO level of the hole-type host material is d1 according to an embodiment of the present disclosure.

Fig. 8 is a schematic diagram when the difference between the LUMO level of the electron-type host material and the HOMO level of the hole-type host material is d2 according to the embodiment of the present disclosure.

Fig. 9 is an electroluminescence spectrum of the second light-emitting layer when a difference between a LUMO level of the electron-type host material and a HOMO level of the hole-type host material according to the embodiment of the present disclosure is d 1.

Fig. 10 is an electroluminescence spectrum of the second light-emitting layer when the difference between the LUMO level of the electron-type host material and the HOMO level of the hole-type host material according to the embodiment of the present disclosure is d2.

Fig. 11 is a schematic cross-sectional view of a display panel according to an embodiment of the present disclosure.

In the figure: 1-array substrate, 11-substrate, 12-buffer layer, 13-driving circuit layer, 131-active layer, 1311-active part, 132-gate insulating layer, 133-gate layer, 1331-gate, 134-interlayer dielectric layer, 135-source drain metal layer, 1351-source, 1352-drain, 136-protective layer, 137-planarization layer, 2-pixel layer, 21-pixel defining layer, 22-light emitting device, 221-first electrode, 222-light emitting layer group, 2221-first light emitting layer, 2222-second light emitting layer, 2223-charge generating layer, 2224-first hole transporting layer, 2225-first electron transporting layer, 2226-second hole transporting layer, 2227-second electron transporting layer, 2228-hole injecting layer, 2229-electron injecting layer; 223-a second electrode, 3-an encapsulation layer group, 31-a first inorganic encapsulation layer, 32-an organic encapsulation layer, 33-a second inorganic encapsulation layer, 4-a color film substrate, 41-a black matrix, 42-a sub-filtering unit and 43-an encapsulation substrate.

Detailed Description

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and thus their detailed description will be omitted. Furthermore, the drawings are merely schematic illustrations of the present disclosure and are not necessarily drawn to scale.

Although relative terms, such as "upper" and "lower," may be used herein to describe one element of an icon relative to another, such terms are used herein for convenience only, e.g., with reference to the orientation of the example illustrated in the drawings. It will be appreciated that if the device of the icon were turned upside down, the element described as "upper" would become the element "lower". When a structure is "on" another structure, it may mean that the structure is integrally formed with the other structure, or that the structure is "directly" disposed on the other structure, or that the structure is "indirectly" disposed on the other structure via another structure.

The terms "a," "an," "the," "said," and "at least one" are used to indicate the presence of one or more elements/components/parts/etc.; the terms "comprising" and "having" are intended to be inclusive and mean that there may be additional elements/components/etc. other than the listed elements/components/etc.; the terms "first," "second," and "third," etc. are used merely as labels, and are not limiting on the number of their objects.

The disclosed embodiments provide a stacked electroluminescent device. As shown in fig. 1 to 10, the stacked electroluminescent device includes a first electrode 221, a second electrode 223, a first light-emitting layer 2221, and a second light-emitting layer 2222, the first electrode 221 being an opaque electrode; the second electrode 223 is a transparent electrode or a semitransparent electrode; the first light-emitting layer 2221 is provided between the first electrode 221 and the second electrode 223; the second light-emitting layer 2222 is provided between the first light-emitting layer 2221 and the second electrode 223; each of the first light emitting layer 2221 and the second light emitting layer 2222 includes an electron type host material, a hole type host material, and a light emitting dopant material, a difference between a LUMO level of the electron type host material of the first light emitting layer 2221 and a HOMO level of the hole type host material is a first energy level difference, a difference between a LUMO level of the electron type host material of the second light emitting layer 2222 and a HOMO level of the hole type host material is a second energy level difference, and the first energy level difference is greater than the second energy level difference.

The first light-emitting layer 2221 is far from the light-emitting side of the light-emitting device, the second light-emitting layer 2222 is close to the light-emitting side of the light-emitting device, the difference between the LUMO level of the electronic-type host material of the first light-emitting layer 2221 and the HOMO level of the hole-type host material is a first energy level difference, the difference between the LUMO level of the electronic-type host material of the second light-emitting layer 2222 and the HOMO level of the hole-type host material is a second energy level difference, and the first energy level difference is larger than the second energy level difference, so that light emitted by carriers through Langevin recombination (Langevin recombination) can be blue-shifted and overlapped with the spectrum of the light-emitting device, the spectrum of the first light-emitting layer 2221 is narrowed, the color purity of the first light-emitting layer 2221 is improved, the total color purity of the stacked electroluminescent device can be improved, and the color gamut coverage is improved.

The first electrode 221 may be a semi-transparent electrode or a transparent electrode, and the second electrode 223 may be a fully-opposite electrode or an opaque electrode. In this case, when the difference between the LUMO level of the electron type host material and the HOMO level of the hole type host material in the second light-emitting layer 2222 is large, the difference between the LUMO level of the electron type host material and the HOMO level of the hole type host material in the first light-emitting layer 2221 is small, and the first energy level difference is smaller than the second energy level difference, the stacked electroluminescent device emits light from the first electrode 221.

It is to be understood that, in both the first electrode 221 and the second electrode 223 as the transparent electrode or the semi-transparent electrode, light is emitted from the transparent electrode or the semi-transparent electrode, and a difference between a LUMO level of the electron-type host material and a HOMO level of the hole-type host material of the light emitting layer on a side away from the transparent electrode or the semi-transparent electrode is larger than a difference between a LUMO level of the electron-type host material and a HOMO level of the hole-type host material of the light emitting layer on a side close to the transparent electrode or the semi-transparent electrode.

As shown in fig. 1, the stacked electroluminescent device includes a first electrode 221, a light-emitting layer group 222, and a second electrode 223, the first electrode 221 is an opaque electrode, the second electrode 223 is a transparent electrode or a semitransparent electrode, the first electrode 221 and the second electrode 223 are disposed opposite to each other, the light-emitting layer group 222 includes a first hole transport layer 2224, a first light-emitting layer 2221, a charge generation layer 2223, a second light-emitting layer 2222, and a first electron transport layer 2225, the charge generation layer 2223 is located between the first electrode 221 and the second electrode 223, the first light-emitting layer 2221 is located between the first electrode 221 and the charge generation layer 2223, the second light-emitting layer 2222 is located between the charge generation layer 2223 and the second electrode 223, the first hole transport layer 2224 is located between the first electrode 221 and the first light-emitting layer 2221, and the first electron transport layer 2225 is located between the second light-emitting layer 2222 and the second electrode 223.

As shown in fig. 2, in an implementable embodiment, the stacked electroluminescent device may further include a second hole transporting layer 2226 and a second electron transporting layer 2227, the second hole transporting layer 2226 being located between the charge generating layer 2223 and the second light emitting layer 2222; the second electron transport layer 2227 is located between the first light emitting layer 2221 and the charge generation layer 2223. As shown in fig. 3 and 4, the stacked electroluminescent device may further include a hole injection layer 2228 or an electron injection layer 2229. As shown in fig. 5, the stacked electroluminescent device may also include a hole injection layer 2228 and an electron injection layer 2229, wherein the hole injection layer 2228 is located between the first electrode 221 and the first hole transport layer 2224, and the electron injection layer 2229 is located between the first electron transport layer 2225 and the second electrode 223.

When the second electrode 223 is a translucent electrode, the stacked electroluminescent device may further include a capping layer, where the capping layer is located on a side of the second electrode 223 far from the first electrode 221, and in this case, the second electrode may be a thin metal simple substance and an alloy thereof. Illustratively, the second electrode 223 may be a magnesium silver (MgAg) alloy and may be 10-20nm thick.

When the second electrode 223 is a transparent electrode, the material of the second electrode 223 may be a transparent metal oxide. Illustratively, the metal oxide may be Indium Tin Oxide (ITO), indium Zinc Oxide (IZO), fluorine-doped SnO2 (SnO 2: F, abbreviated as FTO), or the like. Of course, the second electrode 223 may be made of other materials, which are not listed here. Preferably, the material of the second electrode 223 may be Indium Tin Oxide (ITO). The second electrode 223 may be formed by vacuum evaporation, chemical vapor deposition, coating, ink jet, screen printing, or the like, and the second electrode 223 may also be formed by other methods, which are only exemplary and not limiting.

The first electrode 221 includes a metal layer made of silver, aluminum, magnesium, calcium, a silver alloy, an aluminum alloy, a magnesium alloy, or a calcium alloy. Of course, the material of the first electrode 221 is not limited thereto, and may be other materials, which are not listed here. Preferably, the material of the metal layer may be aluminum, silver or magnesium-silver alloy. The first electrode 221 may further include a transparent metal oxide layer, and the first electrode 221 is formed by combining a metal layer and a transparent metal oxide layer, and specifically, the transparent metal oxide layer may be disposed on two opposite sides of the metal layer, for example: ITO/silver/ITO, ITO/silver/ITO means a sandwich structure consisting of a layer of ITO, a layer of silver and a layer of ITO.

The charge generation layer 2223 is composed of an organic material advantageous for carrier generation, the charge generation layer 2223 may be an n-type doped organic layer/inorganic metal oxide, for example, alq3: mg/WO3 or Bphen: li/MoO3, and the charge generation layer 2223 may also be an n-type doped organic layer/single organic layer, for example, alq3: li/HATCN. Of course, the charge generation layer 2223 may be made of other materials, which are merely exemplary and not limiting.

Note that the n-type doped organic layer/inorganic metal oxide means an n-type doped organic layer and an inorganic metal oxide layer which are stacked, the Alq3: mg/WO3 means an Alq3: mg layer and a WO3 layer which are stacked, and the Bphen: li/MoO3 means a Bphen: li layer and a MoO3 layer which are stacked. The n-type doped organic layer/single organic layer means an n-type doped organic layer and a single organic layer which are arranged in a stacked manner, and the Alq3: li/HATCN means an Alq3: li layer and a HATCN layer which are arranged in a stacked manner.

The first electron transport layer 2225 is used to transport electrons from the charge generation layer 2223 to the first light emitting layer 2221, the second electron transport layer 2227 is used to transport electrons from the second electrode 223 to the second light emitting layer 2222, and the first electron transport layer 2225 and the second electron transport layer 2227 generally have higher electron mobility, for example, both the first electron transport layer 2225 and the second electron transport layer 2227 may be TmPyPB or Bphen: and Liq.

The first hole transporting layer 2224 serves to transport holes from the first electrode 221 to the first light emitting layer 2221, the second hole transporting layer 2226 serves to transport holes from the charge generating layer 2223 to the second light emitting layer 2222, and the first hole transporting layer 2224 and the second hole transporting layer 2226 generally have higher hole mobility, for example, each of the first electron transporting layer 2225 and the second electron transporting layer 2227 may be PEDOT: PSS or HATCN/NPB. Wherein, HATCN/NPB means a HATCN layer and an NPB layer which are arranged in a laminated manner.

The first light emitting layer 2221 and the second light emitting layer 2222 of the light emitting device each include a hole type host material, an electron type host material, and a dopant material, where the hole type host material may be CBP, the electron type host material may be TPBi, and the dopant material may be Ir (ppy) 3, and then the first light emitting layer 2221 and the second light emitting layer 2222 may be CBP: TPBi: ir (ppy) 3.

The difference between the LUMO level of the electron type host material and the HOMO level of the hole type host material in the first light-emitting layer 2221 is a first level difference, the difference between the LUMO level of the electron type host material and the HOMO level of the hole type host material in the second light-emitting layer 2222 is a second level difference, and the difference between the first level difference and the second level difference is 0.1eV or more.

The light emitted from the carriers by Langevin recombination (Langevin recombination) is blue-shifted to overlap with the spectrum of the light emitting device itself, thereby narrowing the spectrum. The langevin recombination occurs between the LUMO level of the electron type host material and the HOMO level of the hole type host material, and if the difference between the LUMO level of the electron type host material and the HOMO level of the hole type host material is large, light in the long wavelength direction of the light emitting device is suppressed, and the spectrum becomes narrow.

Since the first light emitting layer 2221 generally faces greater losses due to optical effects, resulting in a reduction in the efficiency of the light emitting device, a broadening of the spectrum, and a reduction in the color gamut. The first electrode 221 is transparent ITO, and the second electrode 223 is opaque Mg: an Ag alloy, a light emitting device emitting green light, is exemplified. Fig. 6 shows electroluminescence spectra of different light emitting layers of the stacked electroluminescent device according to the embodiment of the present disclosure, and table 1 shows parameters of color purity and color gamut of the different light emitting layers.

Table 1 parameters of color purity and color gamut of different light-emitting layers

	Peak wavelength (nm)	Half peak width (nm)	CIE x	CIE y
					A second luminescent layer	526	50.1	0.313	0.647
A first light-emitting layer	526	56.3	0.330	0.629

As can be seen from fig. 6 and table 1, the electroluminescence spectrum L1 of the first light-emitting layer 2221 obviously has a wider half-width than the electroluminescence spectrum L2 of the second light-emitting layer 2222, and for green light, a smaller CIE x and a larger CIE y value are generally required to improve the color gamut. It can be appreciated that the wider first light emitting layer 2221 affects the color purity of the light emitting device, and also limits the improvement of the color gamut. It is apparent that the second light emitting layer 2222 has significant color purity and color gamut advantages.

Fig. 7 is a schematic diagram when the difference between the LUMO level of the electron-type host material and the HOMO level of the hole-type host material is d1 according to an embodiment of the present disclosure. Fig. 8 is a schematic diagram when the difference between the LUMO level of the electron-type host material and the HOMO level of the hole-type host material is d2 according to the embodiment of the present disclosure. It can be seen that d1 is greater than d2. In fig. 7 and 8, a represents a hole type host material, B represents an electron type host material, and C represents a dopant material.

Fig. 9 shows an electroluminescence spectrum L3 of the second light-emitting layer when the difference between the LUMO level of the electron-type host material and the HOMO level of the hole-type host material according to the embodiment of the present disclosure is d 1. Fig. 10 shows an electroluminescence spectrum L4 of the second light-emitting layer when the difference between the LUMO level of the electron-type host material and the HOMO level of the hole-type host material according to the embodiment of the present disclosure is d2. Table 2 shows the emission performance parameters of the second light-emitting layer in the case where the LUMO level of the electron-type host material is different from the HOMO level of the hole-type host material.

Table 2 light emitting performance parameters of the second light emitting layer when the difference between the LUMO level of the electron type host material and the HOMO level of the hole type host material is two of d1 and d2.

	HOMO energy level	LUMO energy level	Difference of energy level	Peak wavelength (nm)	Peak width (nm)
						Case 1	5.34	2.86	2.48	620	36.0
Case 2	5.34	2.96	2.38	620	37.5

The light-emitting device emits red light, but the light-emitting device may emit blue light or green light, and is not particularly limited herein. As can be seen from fig. 9, 10, and table 2, when the difference between the LUMO level of the electron-type host material and the HOMO level of the hole-type host material is small, the light emission in the long wavelength direction of the light emitting device tends to be stronger, and generally has a wider half-peak width.

The HOMO levels of the electron-type host material and the hole-type host material may be measured by an AC3 device, or by cyclic voltammetry; the LUMO energy levels of the electron-type host material and the hole-type host material may be obtained by subtracting the energy band width of the material, which may be obtained from the absorption edge of the test material, from the HOMO energy level.

The half-width of the emission spectrum of the first light-emitting layer 2221 is narrower than the half-width of the emission spectrum of the second light-emitting layer 2222 by 1 to 10nm. By narrowing the spectrum away from the first light emitting layer 2221, a narrower spectrum of the entire light emitting device is achieved.

Table 3 shows the emission spectra, color coordinates and efficiency parameters of the first light-emitting layer using the pre-and post-narrowing stacked devices. Before the first light-emitting layer is narrowed, the difference between the LUMO level of the electron-type host material and the HOMO level of the hole-type host material is small; after the first light-emitting layer is narrowed, the difference between the LUMO level of the electron-type host material and the HOMO level of the hole-type host material is large.

Table 3 luminescence spectrum, color coordinates and efficiency parameters of the first luminescence layer using the pre-narrowing and post-narrowing stacked devices

The half-peak widths of the emission spectrum of the first light-emitting layer 2221 before and after narrowing are 56.3nm and 53.8nm, respectively, and it can be seen that by narrowing the spectrum far from the first light-emitting layer 2221, a narrower spectrum of the entire light-emitting device can be realized, and higher efficiency is facilitated to be realized.

Further, the efficiency of the device can be further improved by using a top-emitting microcavity structure after the spectrum is narrowed, and the result is omitted here.

The intrinsic spectrum or half-peak width of the electroluminescent spectrum of the dopant material of the first light emitting layer 2221 is 1 to 10nm narrower than the intrinsic spectrum or half-peak width of the electroluminescent spectrum of the dopant material of the second light emitting layer 2222. That is, the doping material of the first light emitting layer 2221 and the doping material of the second light emitting layer 2222 may be different, and a narrower spectrum of the light emitting device is realized with a doping material having a narrow spectrum.

For example, the doping material of the first light emitting layer 2221 may be DABNA-1, whose electroluminescence wavelength peak and half-peak width are 459nm and 28nm, respectively; the doping material of the second light emitting layer 2222 may be B2, whose electroluminescence wavelength peak and half-peak width are 460nm and 37nm, respectively. Obviously, the combination of the first light-emitting layer 2221 and the second light-emitting layer 2222 using B2 as a dopant can significantly reduce the half-peak width of the light-emitting spectrum of the stacked device, and thus a narrower spectrum can be achieved.

It can be understood that by changing the difference between the LUMO energy levels of different light-emitting layers and the HOMO energy level of the hole-type host material, the half-peak width of the light-emitting spectrum, and the intrinsic spectrum of the dopant material or the half-peak width of the electroluminescence spectrum, the improvement of the light-emitting efficiency, the narrowing of the spectrum, and the improvement of the color gamut of the stacked electroluminescent device are achieved.

The embodiment of the disclosure also provides a display panel. As shown in fig. 11, the display panel includes an array substrate 1 and a pixel layer 2, the array substrate 1 includes a substrate 11, a buffer layer 12 is disposed on one side of the substrate 11, a driving circuit layer is disposed on one side of the buffer layer 12 away from the substrate 11, and the pixel layer 2 is disposed on one side of the driving circuit layer away from the substrate 11.

In one embodiment of the present disclosure, the base substrate 11 may be an inorganic base substrate or an organic base substrate. For example, in one embodiment of the present disclosure, the material of the substrate 11 may be a glass material such as soda-lime glass (soda-lime glass), quartz glass, or sapphire glass, or may be a metal material such as stainless steel, aluminum, or nickel.

In another embodiment of the present disclosure, the material of the substrate base plate 11 may be Polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), polyvinyl phenol (PVP), polyether sulfone (PES), polyimide, polyamide, polyacetal, polycarbonate (PC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or a combination thereof.

In another embodiment of the present disclosure, the substrate 11 may also be a flexible substrate, for example, the material of the substrate 11 may be Polyimide (PI). The substrate 11 may also be a composite of multiple layers of materials, for example, in an embodiment of the present disclosure, the substrate 11 may include a Bottom Film layer (Bottom Film), a pressure sensitive adhesive layer, a first polyimide layer, and a second polyimide layer, which are sequentially stacked.

The driving circuit layer 13 may include a plurality of driving circuit regions. Any one of the driving circuit regions may include a transistor and a storage capacitor. The transistor may be a thin film transistor, and the thin film transistor may be selected from a top gate type thin film transistor, a bottom gate type thin film transistor, or a dual gate type thin film transistor.

The material of the active layer of the thin film transistor can be amorphous silicon semiconductor material, low-temperature polycrystalline silicon semiconductor material, metal oxide semiconductor material, organic semiconductor material or other types of semiconductor material; the thin film transistor may be an N-type thin film transistor or a P-type thin film transistor.

The transistor may have a first terminal, a second terminal, and a control terminal, one of the first terminal and the second terminal may be a source region and the other may be a drain region of the transistor, and the control terminal may be a gate of the transistor. It is understood that the source region and the drain region of a transistor are two concepts that are opposite and can be switched with each other; when the operating state of the transistor changes, for example the direction of the current flow changes, the source and drain regions of the transistor can be interchanged.

In the present disclosure, the driving circuit layer 13 may include a transistor layer, an interlayer dielectric layer 134, and a source-drain metal layer 135 sequentially stacked on the substrate 11. The transistor layer is provided with an active portion and a gate of the transistor, and the source-drain metal layer 135 is electrically connected to a source and a drain of the transistor. Alternatively, the transistor layers may include an active layer 131, a gate insulating layer 132, and a gate layer 133 stacked between the substrate 11 and the interlayer dielectric layer 134. The position relation of each film layer can be determined according to the film layer structure of the thin film transistor.

In some embodiments, the active layer 131 may be used to form an active portion 1311 of a transistor, and the active portion 1311 of a semiconductor includes a channel region and source and drain regions at both sides of the channel region; wherein the channel region may retain semiconductor properties and the semiconductor material of the source and drain regions is partially or fully conductive. The gate layer 133 may be used to form a gate layer trace such as a scan trace, a gate of a transistor, and a part or all of electrode plates of a storage capacitor. The source-drain metal layer 135 may be used to form source-drain metal layer traces such as source, drain, data traces, power traces, and the like.

Taking a top gate type thin film transistor as an example, the thin film transistor may include an active portion 1311, a gate insulating layer 132, a gate 1331, a source electrode 1351, and a drain electrode 1352, wherein:

the active portion 1311 is disposed on one side of the substrate 11, and may be made of polysilicon, amorphous silicon, or the like, and the active portion 1311 may include a channel region and source and drain regions of two different doping types located at both sides of the channel region.

The gate insulating layer 132 may cover the active portion 1311 and the substrate 11, and the material of the gate insulating layer 132 is an insulating material such as silicon oxide.

The gate 1331 is disposed on a side of the gate insulating layer 132 away from the substrate 11 and directly opposite to the active portion 1311, that is, a projection of the gate 1331 on the substrate 11 is located within a projection range of the active portion 1311 on the substrate 11, for example, a projection of the gate 1331 on the substrate 11 coincides with a projection of a channel region of the active portion 1311 on the substrate 11.

The thin film transistor further comprises an interlayer dielectric layer 134, the interlayer dielectric layer 134 is arranged on one side of the gate 1331 far away from the substrate base plate 11, the interlayer dielectric layer 134 covers the gate 1331 and the gate insulating layer 132, and the interlayer dielectric layer 134 is made of an insulating material.

A source 1351 and a drain 1352 are disposed on the surface of the interlayer dielectric layer 134 away from the substrate 11, the source 1351 and the drain 1352 are connected to the active portion 1311, for example, the source 1351 and the drain 1352 are respectively connected to a source region and a drain region of the corresponding active portion 1311 through vias.

A protective layer 136 is provided on the sides of the source and drain electrodes 1351 and 1352 remote from the substrate base 11, and the protective layer 136 covers the source and drain electrodes 1351 and 1352. The source electrode 1351 and the drain electrode 1352 are provided with a planarization layer 137 on the side away from the substrate 11, the planarization layer 137 is provided on the side of the protection layer 136 away from the substrate 112, the planarization layer 137 covers the protection layer 136, and the surface of the planarization layer 137 away from the substrate 11 is a plane.

The pixel layer 2 includes a pixel defining layer 21 and a plurality of light emitting devices 22, the pixel defining layer 21 is disposed on one side of the substrate 11, a plurality of pixel openings 2311 are disposed on the pixel defining layer 21, and the plurality of light emitting devices 22 are respectively disposed in the pixel openings 2311 and located in the light emitting areas 100. The different light emitting devices 22 are controlled to emit light by the driving circuit layer 13, so that the pixel layer 2 performs a function of image display.

Specifically, the source electrode 1351 may be connected to the first electrode 221 of the light emitting device 22, and the light emitting device 22 may be driven to emit light by applying a signal to the first electrode 221, and a specific light emitting principle will not be described in detail herein. At least part of the light-emitting device can adopt any one of the laminated electroluminescent devices, and the structure and the materials of the laminated electroluminescent device are described in detail, so that the detailed description is omitted.

The rest of the light emitting devices can adopt conventional light emitting devices, and the light emitting layer of the conventional light emitting device can comprise a single host material and a doping material or only comprise a single light emitting material. When the light emitting layer is composed of a single host material and a dopant material, the specific composition of the light emitting layer may be mCP: ir (piq) 3; when the light emitting layer is composed of only a single light emitting material, the light emitting layer may be specifically Alq3.

In general, when image display is implemented, the light emitting devices 22 need to be formed into a plurality of pixels, each pixel may generally include three light emitting devices 22 of different colors, and the light emitting devices 22 may be classified into a red light emitting device, a green light emitting device, and a blue light emitting device according to the different light emitting colors.

The side of the pixel layer 2 away from the substrate 131 is provided with a packaging layer group 3, so that the pixel layer 2 is covered to prevent water and oxygen corrosion. The encapsulation layer group 3 may have a single-layer or multi-layer structure, and the material of the encapsulation layer group 3 may include an organic or inorganic material, which is not particularly limited herein.

In this embodiment, the encapsulation layer group 3 may include a first inorganic encapsulation layer 31, an organic encapsulation layer 32 and a second inorganic encapsulation layer 33, the first inorganic encapsulation layer 31 is disposed on a side of the pixel layer 2 away from the substrate 131, the organic encapsulation layer 32 is disposed on a side of the first inorganic encapsulation layer 31 away from the substrate 131, and the second inorganic encapsulation layer 33 is disposed on a side of the organic encapsulation layer 32 away from the substrate 131.

The color filter substrate 4 may be disposed on a side of the package layer group 3 away from the driving backplane 22, where the color filter substrate 4 includes a package substrate 43, a black matrix 41 is disposed on one side of the package substrate 43, an opening region array is defined on the black matrix 41, the opening region array includes a plurality of opening region rows arranged in a row direction, each opening region row includes a plurality of opening regions, a sub-filter unit 42 is disposed in each opening region, two adjacent sub-filter units 42 in each opening region row have different colors, a plurality of sub-filter units 42 in a same opening region row constitute a plurality of filter units, and usually one filter unit 240 may include a red sub-filter unit, a green sub-filter unit, and a blue sub-filter unit.

The disclosed embodiments also provide a display device, which may include the display panel of any one of the above embodiments of the present disclosure. The detailed structure and advantages of the display panel have been described in detail earlier, and therefore, the detailed description thereof is omitted.

It should be noted that the display device includes other necessary components and components besides the display panel, such as a housing, a circuit board, a power line, and the like, and those skilled in the art can supplement the display device accordingly according to the specific use requirement of the display device, and the description thereof is omitted.

When the display panel has the structure shown in fig. 11, the display device may be a conventional electronic device, such as: mobile phones, computers, televisions, video recorders and video players, and also emerging wearable devices, such as: virtual reality devices and augmented reality devices, not to be enumerated herein.

Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

Claims (14)

1. A laminated electroluminescent device, comprising:

a first electrode which is an opaque electrode;

the second electrode is a transparent electrode or a semitransparent electrode;

a first light-emitting layer provided between the first electrode and the second electrode;

a second light-emitting layer provided between the first light-emitting layer and the second electrode;

the first light-emitting layer and the second light-emitting layer both comprise an electron type host material, a hole type host material and a light-emitting doping material, the difference between the LUMO energy level of the electron type host material of the first light-emitting layer and the HOMO energy level of the hole type host material is a first energy level difference, the difference between the LUMO energy level of the electron type host material of the second light-emitting layer and the HOMO energy level of the hole type host material is a second energy level difference, and the first energy level difference is larger than the second energy level difference.

2. The stacked electroluminescent device of claim 1, wherein the difference between the first energy level difference and the second energy level difference is 0.1eV or more.

3. The laminated electroluminescent device according to claim 1, wherein the half-width of the emission spectrum of the first light-emitting layer is 1 to 10nm narrower than the half-width of the emission spectrum of the second light-emitting layer.

4. The stacked electroluminescent device according to claim 1, wherein the intrinsic spectrum or half-width of the electroluminescence spectrum of the light emitting dopant material of the first light emitting layer is 1 to 10nm narrower than the intrinsic spectrum or half-width of the electroluminescence spectrum of the light emitting dopant material of the second light emitting layer.

5. The laminated electroluminescent device of claim 1, further comprising:

a charge generation layer provided between the first light-emitting layer and the second light-emitting layer;

a first hole transport layer provided between the first electrode and the first light emitting layer;

and the first electron transport layer is arranged between the second light-emitting layer and the second electrode.

6. The laminated electroluminescent device of claim 5, further comprising:

a second hole transport layer disposed between the charge generation layer and the second light emitting layer;

a second electron transport layer disposed between the first light emitting layer and the charge generation layer.

7. The laminated electroluminescent device of claim 6, further comprising:

a hole injection layer disposed between the first electrode and the first hole transport layer;

and/or an electron injection layer disposed between the first electron transport layer and the second electrode.

8. The laminated electroluminescent device of claim 1, wherein when the second electrode is a translucent electrode, the laminated electroluminescent device further comprises a capping layer disposed on a side of the second electrode away from the first electrode.

9. The stacked electroluminescent device according to claim 1, wherein the material of the second electrode is a transparent metal oxide, a metal simple substance or a metal alloy.

10. The laminated electroluminescent device of claim 1, wherein the first electrode comprises a metal layer, and the material of the metal layer is silver, aluminum, magnesium, calcium, silver alloy, aluminum alloy, magnesium alloy, or calcium alloy.

11. The laminated electroluminescent device of claim 10, wherein the first electrode further comprises a transparent metal oxide layer disposed on opposite sides of the metal layer.

12. The stacked electroluminescent device according to claim 5, wherein the charge generation layer comprises an n-type doped organic layer and an inorganic metal oxide, or the charge generation layer comprises an n-type doped organic layer and a single organic layer.

13. A display panel, comprising:

an array substrate;

a light emitting layer set disposed on one side of the array substrate, the light emitting layer set comprising the stacked electroluminescent device according to any one of claims 1 to 12.

14. A display device characterized by comprising the display panel according to claim 13.

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