CN115440910A

CN115440910A - Light emitting device, display panel and display apparatus

Info

Publication number: CN115440910A
Application number: CN202211269086.9A
Authority: CN
Inventors: 尤娟娟; 全威; 许程; 周丹丹
Original assignee: BOE Technology Group Co Ltd
Current assignee: BOE Technology Group Co Ltd
Priority date: 2022-10-17
Filing date: 2022-10-17
Publication date: 2022-12-06

Abstract

The embodiment of the application provides a light-emitting device, a display panel and a display device. The light emitting device includes: a first electrode, a first light emitting unit, and a second electrode stacked; the first light emitting unit includes a first color light emitting layer and a second color light emitting layer; each film layer between the first electrode and the second electrode forms an optical cavity for transmitting light with the designed wavelength from the first electrode or the second electrode; the second color light emitting layer comprises a first host material and a doping material; the first host material includes a hole transport material having a highest occupied molecular orbital level less than a highest occupied molecular orbital level of the dopant material. The light emitting device provided by the embodiment of the application realizes reducing the difference between the luminous intensities of the luminous layers with two colors through two modes of optical adjustment and electrical adjustment, so that the power consumption of the sub-pixels corresponding to the first color and the power consumption of the sub-pixels corresponding to the second color are closer, the yield of the light emitting device can be improved, and the luminous effect can be improved.

Description

Light emitting device, display panel and display apparatus

Technical Field

The application relates to the technical field of light-emitting devices, in particular to a light-emitting device, a display panel and a display device.

Background

White Organic Light-Emitting Diode (WOLED) technology is not limited by Fine Metal Mask (FMM), and has wide application prospect in large-size and super-large-size display fields or ultra-high resolution augmented reality/virtual display fields.

The WOLED technology uses a white light emitting device in combination with a color filter to realize full color display. The color filter commonly used for the WOLED is of an absorption type, transmits light of certain colors, absorbs light of other colors, realizes selective filtering of light of specific colors, and causes the WOLED to have larger light loss and more loss power consumption. Therefore, power consumption is an important measure of the performance of WOLEDs.

In the related art, a light emitting unit is disposed between a first electrode and a second electrode of a WOLED light emitting device, and when one light emitting unit includes light emitting layers of multiple colors, the difference between light emitting ratios of the colors is large, which results in a large difference between light intensities of the colors, and further results in too high power consumption of a sub-pixel corresponding to at least one color or too high power consumption of the whole OLED device, which affects the performance of the WOLED.

Disclosure of Invention

The application provides a light-emitting device, a display panel and a display device aiming at the defects of the prior art, and aims to solve the technical problem that the difference of the light-emitting proportions of multiple colors in a light-emitting unit is large in the prior art.

In a first aspect, embodiments of the present application provide a light emitting device including a first electrode, a first light emitting unit, and a second electrode that are stacked;

the first light emitting unit includes a first color light emitting layer and a second color light emitting layer;

each film layer between the first electrode and the second electrode forms an optical cavity for transmitting light with the designed wavelength from the first electrode or the second electrode;

the second color light emitting layer comprises a first host material and a doping material; the first host material includes a hole transport material having a highest occupied molecular orbital level less than a highest occupied molecular orbital level of the dopant material.

In some possible embodiments, the energy level difference between the highest occupied molecular orbital level of the hole transport material and the highest occupied molecular orbital level of the dopant material is not less than 0.2eV and not more than 0.5eV.

In some possible embodiments, the second color light emitting layer further comprises a second host material comprising an electron transport material;

the doping material is doped in the hole transport material and the electron transport material.

In some possible embodiments, at least one of the following is included:

the thickness of the optical cavity is proportional to the design wavelength;

the refractive index of the optical cavity is proportional to the design wavelength.

In some possible implementations, the design wavelength is no greater than 577 nanometers and no less than 492 nanometers.

In some possible embodiments, the first electrode is an anode and the second electrode is a cathode;

the first color light emitting layer is closer to the first electrode than the second color light emitting layer.

In some possible embodiments, the light emitting device further includes:

a first blue light emitting unit and a first charge generation layer laminated between the first electrode and the first color light emitting layer in a direction away from the first electrode;

a second charge generation layer and a second blue light emitting unit laminated between the second color light emitting layer and the second electrode in a direction away from the second color light emitting layer;

the first color light emitting layer is a red light emitting layer, and the second color light emitting layer is a green light emitting layer.

In a second aspect, an embodiment of the present application further provides a display panel, including: any of the light emitting devices as provided in the first aspect above.

In some possible embodiments, the display panel further includes: and the color filter is positioned on the light-emitting side of the light-emitting device.

In a third aspect, an embodiment of the present application further provides a display device, including: a display panel as provided in the second aspect above.

The beneficial technical effects brought by the technical scheme provided by the embodiment of the application comprise:

in the light emitting device provided by the embodiment of the application, the first light emitting unit comprises a first color light emitting layer and a second color light emitting layer, the two color light emitting layers are located in the same light emitting unit, the difference between the light emitting intensities of the light emitting layers with two colors is reduced by two modes of optical adjustment and electrical adjustment, and then the power consumption of the sub-pixels corresponding to the first color and the power consumption of the sub-pixels corresponding to the second color are closer, so that the requirements on corresponding good product indexes are favorably met, and the yield of the light emitting device can be improved.

Moreover, the light emitted by the white light sub-pixel finally formed by the light-emitting device provided by the embodiment of the application is closer to the target color point, the problem of color cast caused by uneven light intensity of two colors in the same light-emitting unit can be solved to a great extent, and the light-emitting effect is improved. In addition, the proportion of the light of the first color emitted by the light-emitting device to the light of the second color is relatively balanced, so that the white light obtained by mixing the whole light-emitting device is very close to the target color point of the white light, other sub-pixels are basically not required to be used for color complementation, the power consumption required by color complementation is saved, and the power consumption of the display panel can be reduced as a whole.

Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.

Drawings

The foregoing and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 is a schematic structural diagram of a light emitting device provided in an embodiment of the present application;

fig. 2 is a schematic structural diagram of another light-emitting device provided in an embodiment of the present application;

FIG. 3 is a graph comparing spectra of a display panel according to an embodiment of the present application and a display panel according to the related art;

fig. 4 is a power consumption comparison diagram of a display panel provided in an embodiment of the present application and a display panel in the related art.

Reference numerals are as follows:

100-a light emitting device;

110-a first electrode;

120-a first blue light emitting cell;

121-hole injection layer; 122 — first hole transport layer; 123-a first electron blocking layer; 124-a first blue light emitting layer; 125-first hole blocking layer; 126-first electron transport layer;

130-a first charge generation layer;

131-a first N-type charge generation layer; 132-a first P-type charge generation layer;

140-a first light emitting unit;

141-a second hole transport layer; 142-a second electron blocking layer; 143-a first color light emitting layer; 144-a second color emissive layer; 145-a second hole blocking layer; 146-a second electron transport layer;

150-a second charge generation layer;

151-second N-type charge generation layer; 152-a second P-type charge generation layer;

160-second blue light emitting unit;

161-third hole transport layer; 162-a third electron blocking layer; 163-a second blue light emitting layer; 164-a third hole blocking layer; 165-a third electron transport layer; 166-electron injection layer;

170-second electrode.

Detailed Description

Embodiments of the present application are described below in conjunction with the drawings in the present application. It should be understood that the embodiments set forth below in connection with the drawings are exemplary descriptions for explaining technical solutions of the embodiments of the present application, and do not limit the technical solutions of the embodiments of the present application.

As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. The term "and/or" as used herein means at least one of the items defined by the term, e.g., "a and/or B" may be implemented as "a", or as "B", or as "a and B".

To make the objects, technical solutions and advantages of the present application more clear, embodiments of the present application will be described in further detail below with reference to the accompanying drawings.

In the related technology, the light emitting layers of at least two colors are positioned in the same light emitting unit, the light intensities of the emitted colors are uneven, the power consumption difference of the sub-pixels corresponding to the colors is large when the target color point is reached, and the specific expression is that the power consumption of the sub-pixel corresponding to one color is particularly high and does not accord with the good index of the sub-pixel, so that the performance of the WOLED light emitting device is influenced.

In some light emitting devices, the first electrode and the second electrode are shared by the sub-pixels in each pixel unit, so that the brightness of each sub-pixel in the pixel unit cannot be independently adjusted, and the light emitting intensity of the first color light emitting layer and the second color light emitting layer is not uniform, which causes a serious color cast problem of the WOLED.

In some light emitting devices, each sub-pixel in each pixel unit has a separate first electrode and/or second electrode, so that the brightness of each sub-pixel can be adjusted separately, but the light emitted by the white sub-pixel in the WOLED is difficult to reach the target color point, and therefore, the light emitted by other sub-pixels needs to be increased for color compensation, thereby increasing the power consumption of the WOLED light emitting device.

Therefore, the light intensities of at least two colors in the same light emitting unit need to be adjusted, and particularly, the light emitting efficiency of one of the color light emitting layers with higher power consumption and lower light intensity can be adjusted. However, the light emitting layers of the colors in the same light emitting unit share the functional layers such as the hole transport layer and the electron transport layer, so the number of electrons and holes is constant, the total efficiency of light emission is constant, if the light emitting efficiency of one color is to be reduced, the light emitting efficiency of the other color is increased, the light intensities of the two colors are always different, and the power consumption is also different, so that the difference between the light emitting efficiencies of the colors is difficult to be reduced.

The application provides a light emitting device, display module and display device aims at solving prior art technical problem as above.

The following describes the technical solutions of the present application and how to solve the above technical problems with specific embodiments. It should be noted that the following embodiments may be referred to, referred to or combined with each other, and the description of the same terms, similar features, similar implementation steps, etc. in different embodiments is not repeated.

Referring to fig. 1, an embodiment of the present application provides a light emitting device 100 including a first electrode 110, a first light emitting unit 140, and a second electrode 170, which are stacked.

The first light emitting unit 140 includes a first color emitting layer 143 and a second color emitting layer 144.

Each film layer between the first electrode 110 and the second electrode 170 forms an optical cavity for transmitting light of a design wavelength out of the first electrode 110 or the second electrode 170.

The second color light emitting layer 144 includes a first host material and a dopant material. The first host material includes a hole transport material having a highest occupied molecular orbital level less than a highest occupied molecular orbital level of the dopant material.

In this embodiment, the first light emitting unit 140 includes a first color light emitting layer 143 and a second color light emitting layer 144, and the two color light emitting layers are located in the same light emitting unit, and the difference between the light emitting intensities of the two color light emitting layers is reduced by two ways of optical adjustment and electrical adjustment, so that the power consumption of the sub-pixel corresponding to the first color and the power consumption of the sub-pixel corresponding to the second color are closer to each other, and various corresponding good product indexes are satisfied, thereby improving the yield of the light emitting device 100. Further, the light emitted by the white light sub-pixel finally formed by the light emitting device 100 provided by the embodiment of the application is closer to the target color point, so that the problem of color cast caused by uneven light intensity of two colors in the same light emitting unit can be solved to a great extent, and the light emitting effect is improved. In addition, since the light of each color emitted by the light emitting device 100 has a stable proportion, the white light obtained by mixing the light is very close to the color point of the white light, and other sub-pixels are basically not needed to be used for color compensation, so that the power consumption required by color compensation is saved, and the power consumption of the light emitting device 100 can be reduced as a whole.

In this embodiment, the optical modulator can form an optical cavity between the first electrode 110 and the second electrode 170, the resonance wavelength corresponding to the resonance condition of the optical cavity corresponds to the design wavelength, the light emitted from the light-emitting layer can generate the microcavity effect in the optical cavity, and the light having the design wavelength corresponding to the resonance wavelength can be further extracted, so as to enhance the light emission intensity of the light having the design wavelength. The light of the second color in this embodiment has a designed wavelength, and therefore the light intensity of the second color can be enhanced by optical adjustment.

Optionally, by adjusting the thickness of each film structure between the first electrode 110 and the second electrode 170, the distance between the first electrode 110 and the second electrode 170 is adjusted, and then the thickness of the optical cavity is adjusted, the resonant wavelength of the optical cavity is determined, and then the light that can be enhanced by the optical cavity can be determined.

The microcavity effect mainly means that photon densities of different energy states are redistributed, so that only light with a designed wavelength can be emitted at a specific angle after conforming to a resonant cavity mode, further extraction of the light with the designed wavelength is realized, the light intensity of the light with the designed wavelength is enhanced, the light emitting efficiency of the light with the designed wavelength is improved, and further, the power consumption of a sub-pixel corresponding to the light with the designed wavelength is reduced.

Optionally, the electrical adjustment in this embodiment is embodied by adjusting the electrical parameter of the second color light emitting layer 144, and further adjusting the light emitting ratio of two colors in the same light emitting unit, so as to achieve the effect of adjusting the difference between the light emitting intensities of the two colors to be larger. Alternatively, a first host material including a hole transport material is used in the second color light-emitting layer 144, the highest occupied orbital level (HOMO level) of the hole transport material is deep, the HOMO level of the dopant material is shallow, and the dopant material functions as a trap to reduce the hole transport speed, so that electrons are transported to a position close to the boundary between the first color light-emitting layer 143 and the second color light-emitting layer 144 and are then recombined with holes; this corresponds to moving the recombination position of the holes and the electrons from the second color emission layer 144 to a position near the boundary between the first color emission layer 143 and the second color emission layer 144.

It is understood that the host material does not emit light, and transfers energy of excitons generated after recombination of electrons and holes to the light-emitting guest material to emit light, and different light-emitting guest materials can emit light of different wavelengths to show different colors.

Therefore, in the present embodiment, the doping material is a light emitting guest material of the second color light emitting layer 144, and can receive the energy transmitted by the host material to emit the light of the second color. That is, in the second color light emitting layer 144, the recombination region of the electrons and the holes is closer to the first color light emitting layer 143, so that the energy of the excitons generated after the recombination of the electrons and the holes is more easily transferred to the light emitting guest material in the first color light emitting layer 143 than in the conventional case, and further the ratio of the light emission of the first color light emitting layer 143 in the first light emitting unit 140 is increased, and the light intensity of the first color emitted by the first light emitting unit 140 can be increased.

It can be understood that, by means of optical adjustment, mainly increasing the extraction rate of the light of the second color, the effect of enhancing the light intensity of the light of the second color is achieved, but in the process, the optical cavity may change the refraction angle of the light ray (for example, the light of the first color) with a wavelength longer than that of the light of the second color, so that a part of the light of the first color cannot be emitted, that is, there is a certain inhibiting effect on the light of the first color, resulting in the light intensity of the light of the first color being weakened. The light emitting proportion of the first color light is increased through the electric adjustment mode, but the light emitting proportion of the second color light is also reduced, and further the light intensity of the second color light is reduced. Therefore, the difference between the final light emitting intensities of the first color light and the second color light is smaller and tends to be balanced by combining the two adjustment modes, and the difference between the power consumption is smaller, so that the yield of the light emitting device 100 can be improved, and the performance of the light emitting device 100 can be improved.

Optionally, the light emitting device 100 provided herein is a white light emitting device 100.

In the embodiment, the energy level difference between the hole transport material and the doping material is in a range of 0.2eV to 0.5eV (inclusive), which can control the hole transport speed to some extent, and thus control the recombination position of electrons and holes in the first light emitting unit 140. The situation that holes are difficult to enter the second color light-emitting layer 144 and are difficult to be combined with electrons due to too large energy level difference can be avoided to a certain extent, the recombination effectiveness of the electrons and the holes can be increased, the light-emitting efficiency of the first light-emitting unit 140 can be improved, the light-emitting efficiency of at least one of the first color light-emitting layer 143 and the second color light-emitting layer 144 can be improved, and the power consumption of the light-emitting device 100 can be reduced.

In some possible embodiments, the second color light emitting layer 144 further includes a second host material including an electron transport material.

In this embodiment, the second color light emitting layer 144 uses a mixed host material of a first host material and a second host material, and the dopant material is a guest material or a light emitting material and is doped in the mixed host material. By mixing the material having the electron-transporting property and the material having the hole-transporting property, a carrier recombination region is increased as compared with a single host material, and at the same time, a role of diluting excitons can be played, so that the efficiency and the lifetime of the light-emitting device 100 can be improved.

Further, the composite region can be controlled more easily by mixing the host materials. The content ratio of the material having the hole-transporting property and the material having the electron-transporting property may be controlled according to actual needs, and the recombination region of electrons and holes in the first light-emitting unit 140 may be controlled by controlling the content ratio or electrical parameter of the two materials, so as to adjust the respective light-emitting ratios of the first color and the second color in the first light-emitting unit 140.

Alternatively, the hole transporting material may be 4,4 '-bis (N-carbazolyl) biphenyl (abbreviated as CBP), the electron transporting material may be 3- (4-biphenyl) -4-phenyl-5- (4-tert-butylphenyl) -1,2,4-triazole (abbreviated as TAZ), the dopant material may be a green-light emitting guest material, may be tris (2-phenylpyridinium-N, C2') iridium (III) (abbreviated as Ir (ppy) 3), an organometallic iridium complex, which is mainly a green-phosphorescent emitting compound, and has a peak of emission at 500 nm to 600 nm.

In some possible embodiments, referring to fig. 1, the first electrode 110 is an anode and the second electrode 170 is a cathode.

The first color light emitting layer 143 is closer to the first electrode 110 than the second color light emitting layer 144.

In the present embodiment, the first color light emitting layer 143 is closer to the first electrode 110, the first electrode 110 can inject holes into the first color light emitting layer 143 under the action of the driving voltage, and when the hole transport is slower under the action of the hole transport material, electrons and holes can be recombined at the interface closer to the first color light emitting layer 143 in the second color light emitting layer 144, that is, the recombination position of electrons and holes is closer to the first color light emitting layer 143 than in the conventional case, so that the probability of energy transfer of excitons to the light emitting guest material of the first color light emitting layer 143 can be increased, and the light emitting ratio of the first color in the first light emitting unit 140 can be increased.

Alternatively, one of the first electrode 110 and the second electrode 170 is a total reflection electrode, and the other is a semi-transparent counter electrode, and an optical resonant cavity (i.e., an optical cavity in the embodiment of the present application) may be formed therebetween.

In some possible embodiments, as shown in fig. 2, the light emitting device 100 further includes:

the first blue light emitting unit 120 and the first charge generation layer 130 are stacked between the first electrode 110 and the first color emission layer 143 in a direction away from the first electrode 110.

The second charge generation layer 150 and the second blue light emitting unit 160 are stacked between the second color light emitting layer 144 and the second electrode 170 in a direction away from the second color light emitting layer 144.

The first color light emitting layer 143 is a red light emitting layer, and the second color light emitting layer 144 is a green light emitting layer.

In the present embodiment, the light emitting device 100 further includes a first blue light emitting unit 120 and a second blue light emitting unit 160 capable of emitting blue light, and the first light emitting unit 140 is disposed between the two blue light emitting units as a mixed light emitting unit capable of emitting light of at least two colors. The first blue light emitting unit 120, the first light emitting unit 140, and the second blue light emitting unit 160 are connected in series through the charge generation layer to form the white light emitting device 100, which can emit white light on the light emitting side. The charge generation layer can provide carriers for the light emitting units on two sides, so that each light emitting unit has carriers from the direction of the two electrodes, and the carriers are combined to realize light emission.

The first color light-emitting layer 143 is a red light-emitting layer and can emit red light, and the second color light-emitting layer 144 is a green light-emitting layer and can emit green light. In the embodiment of the present application, the light emission intensity of green light can be increased by optical adjustment, and the light emission intensity of a part of red light can be suppressed. The emission intensity of red light can be increased and the emission intensity of a part of green light can be decreased by electrical adjustment. The adjustment proportion of two kinds of adjustment methods is inconsistent, can synthesize the light intensity that realizes green light and reduce, the light intensity of red light increases, reduces the intensity difference between the red green light, and then makes the power consumption of each colour be comparatively close when reaching the target color point in the sub-pixel that two kinds of chromatic light correspond, all satisfies the yields index, and reduces the required power consumption of complementary color.

Alternatively, as shown in fig. 1, the first blue light emitting unit 120 is closer to the first electrode 110, and the first blue light emitting unit 120 includes a hole injection layer 121, a first hole transport layer 122, a first electron blocking layer 123, a first blue light emitting layer 124, a first hole blocking layer 125, and a first electron transport layer 126, which are stacked in a direction away from the first electrode 110. The first light emitting unit 140 includes a second hole transport layer 141, a second electron blocking layer 142, a red light emitting layer, a green light emitting layer, a second hole blocking layer 145, and a second electron transport layer 146, which are stacked in a direction away from the first electrode 110. The second blue light emitting unit 160 is closer to the second electrode 170, and the first blue light emitting unit 120 includes a third hole transport layer 161, a third electron blocking layer 162, a second blue light emitting layer 163, a third hole blocking layer 164, a third electron transport layer 165, and an electron injection layer 166, which are stacked in a direction away from the first electrode 110.

Alternatively, the first charge generation layer 130 includes a first P-type charge generation layer 132 and a first N-type charge generation layer 131, the first P-type charge generation layer 132 being closer to the first light emitting unit 140, and the first N-type charge generation layer 131 being closer to the first blue light emitting unit 120.

Alternatively, the second charge generation layer 150 includes a second P-type charge generation layer 152 and a second N-type charge generation layer 151, the second P-type charge generation layer 152 being closer to the second blue light emitting unit 160, and the second N-type charge generation layer 151 being closer to the first light emitting unit 140.

In some possible embodiments, at least one of the following is included:

the thickness of the optical cavity is proportional to the design wavelength.

In this embodiment, a multi-layer film structure is provided between the first electrode 110 and the second electrode 170, such as the light emitting layers and the carrier function layers (such as the hole transport layer, the electron transport layer, etc.) of the colors mentioned in the above embodiments, and the thickness of at least one film layer between the first electrode 110 and the second electrode 170 is adjusted according to the determined thickness between the first electrode 110 and the second electrode 170, so that when the optical cavity satisfies the resonance condition, the refracted light and the reflected light of the light with the designed wavelength in the optical cavity interfere with each other to generate the microcavity resonance effect, thereby emitting the light with the designed wavelength, narrowing the emission spectrum, and enhancing the light emission intensity of the light with the designed wavelength.

Specifically, the resonance condition is λ =4 π nL/(Φ) ₁ +Φ ₂ -2 π m). Where λ is the resonant wavelength, light satisfying this wavelength (e.g., light of the design wavelength in the embodiment of the present application) can be further extracted in the resonant cavity. n is a refractive index of a medium through which light passes, and n of an organic material is generally about 1.8; alternatively, there may be a slight difference in refractive index between the first electrode 110 and the second electrode 170, where n refers to the equivalent refractive index of each film between the first electrode 110 and the second electrode 170. L is the cavity length, which refers to the distance between the first electrode 110 and the second electrode 170 in this embodiment, and may also refer to the sum of the thicknesses of the film layers between the first electrode 110 and the second electrode 170. Phi ₁ +Φ ₂ A combination of phase differences indicating that light is reflected by the reflective electrode and the transflective electrode (which may correspond to the first electrode 110 and the second electrode 170, respectively); m is a positive integer.

In some possible embodiments, the design wavelength is no greater than 577 nanometers and no less than 492 nanometers.

In this embodiment, the design wavelength may be in the green wavelength band, enabling further extraction of green light.

Based on the same inventive concept, the embodiment of the present application further provides a display panel, including: any of the light emitting devices 100 as provided in the previous embodiments.

The display module provided by the present embodiment includes any one of the light emitting devices 100 provided by the above embodiments, and the implementation principle is similar, which is not described herein again.

In some possible embodiments, the display panel further includes: and a color filter positioned at a light emitting side of the light emitting device 100.

In this embodiment, the color filter is located at the light-emitting side of the light-emitting device 100, wherein the light-emitting side may be a side of the first electrode 110 or a side of the second electrode 170, depending on which is an electrode with certain transmittance, so that light emitted from the light-emitting unit can be transmitted. The light emitted by the light emitting device 100 is white light, and can selectively transmit light of various colors after passing through the color filter, for example, a red sub-pixel corresponding to red light, a green sub-pixel corresponding to green light, a blue sub-pixel corresponding to blue light, a white sub-pixel corresponding to white light, and a red sub-pixel, a green sub-pixel, a blue sub-pixel, and a white sub-pixel that are transmitted through the color filter can form a pixel unit to emit white light, and the white light emitted by the light emitting device 100 can be adjusted by adjusting the light emitting ratio to reach a target color point, which can be understood as the white color temperature or white light illuminance required by the WOLED.

Referring to the spectrum chart in fig. 3, the horizontal axis represents the wavelength range (nanometers, nm) of light, the vertical axis represents the emission intensity, which may be a numerical value expressed as a relative value with respect to the maximum value of the EL spectrum, spectrum 1 is the emission spectrum of the light emitting device 100 in the related art (i.e., before improvement), and spectrum 2 is the emission spectrum of the light emitting device 100 provided in the embodiment of the present application. As can be seen from FIG. 3, the spectrum difference of the blue light band (440 nm-475 nm) is not large, the light intensity of the green light band (492 nm-577 nm) is reduced to a certain extent, which indicates that the light emitting efficiency of the color is reduced, the power consumption is increased, and the light intensity of the red light band (622 nm-760 nm) is enhanced to a certain extent, which indicates that the light emitting efficiency of the color is higher, and the power consumption is reduced. Therefore, the difference between the light intensities in the red and green wavelength bands is reduced, and accordingly, the difference between the power consumptions of the respective sub-pixels is also reduced.

As shown in the table of fig. 4, the power consumption of R, G, B when the Sub-pixels are turned on (Sub-Pixel Brightness) is the power consumption required by the red Sub-Pixel, the power consumption required by the green Sub-Pixel, and the power consumption required by the blue Sub-Pixel when the red Sub-Pixel, the green Sub-Pixel, and the blue Sub-Pixel are connected to form the target color dot. The Power consumption (W Power) corresponding to W represents the Power consumption when the white sub-pixel and other complementary color pixels are combined to form the target color point (for example, if the spectrum of the white sub-pixel is different from the spectrum of the target color point to cause color shift of the white sub-pixel, the complementary color can be performed by the complementary color, so that the mixed light of the white light and the complementary color light approaches the target color point). As can be seen from fig. 4, the power consumption of spectrum 2 is closer to that of spectrums 1,R and G, and the power consumption of R is greatly reduced, which meets the good product index corresponding to the power consumption of the red sub-pixel. And the power consumption corresponding to W is also reduced, which means that in the embodiment of the present application, the power consumption for basically not requiring complementary color or complementary color is very small, the power consumption for complementary color can be omitted, and the power consumption corresponding to the white sub-pixel of the light emitting device 100 is further reduced.

In addition, the power consumption corresponding to the blue sub-pixel in the table of fig. 4 is also reduced because the luminance of the blue light required when the red light and the green light with different ratios are combined into the target color point is different, so the power consumption corresponding to the corresponding blue sub-pixel is also different, and the embodiment of the present application can further reduce the power consumption of the blue light and further reduce the power consumption of the whole light emitting device 100 on the basis of adjusting the light emitting ratio of the red light and the green light.

Based on the same inventive concept, an embodiment of the present application further provides a display device, including: the display panel provided by the previous embodiment.

The display device provided in this embodiment includes any one of the display panels provided in the above embodiments, and the implementation principles thereof are similar, and are not described herein again.

By applying some embodiments of the present application, at least the following beneficial effects can be achieved:

1. the first light emitting unit 140 includes a first color light emitting layer 143 and a second color light emitting layer 144, the two color light emitting layers are located in the same light emitting unit, and the difference between the light emitting intensities of the two color light emitting layers is reduced by optical adjustment and electrical adjustment, so that the power consumption of the sub-pixel corresponding to the first color and the power consumption of the sub-pixel corresponding to the second color are closer to each other, and various corresponding good product indexes are satisfied, thereby improving the good product rate of the light emitting device 100. Further, the light emitted by the white light sub-pixel finally formed by the light emitting device 100 provided by the embodiment of the application is closer to the target color point, so that the problem of color cast caused by uneven light intensity of two colors in the same light emitting unit can be solved to a great extent, and the light emitting effect is improved. In addition, since the light of each color emitted by the light emitting device 100 has a stable proportion, the white light obtained by mixing the light is very close to the color point of the white light, and other sub-pixels are basically not needed to be used for color compensation, so that the power consumption required by color compensation is saved, and the power consumption of the light emitting device 100 can be reduced as a whole.

2. The optical modulator can form an optical cavity between the first electrode 110 and the second electrode 170, the resonance wavelength corresponding to the resonance condition of the optical cavity corresponds to the design wavelength, the light emitted from the light emitting layer can generate a microcavity effect in the optical cavity, the light having the design wavelength corresponding to the resonance wavelength can be further extracted, and the light emitting intensity of the light having the design wavelength can be enhanced. The light of the second color in this embodiment has a designed wavelength, and therefore, the light intensity of the second color can be enhanced by optical adjustment.

3. The electrical adjustment in this embodiment is embodied in adjusting the electrical parameters of the second color light-emitting layer 144, and then adjusting the light-emitting ratio of two colors in the same light-emitting unit, so as to achieve the effect of adjusting the difference between the light-emitting intensities of the two colors, specifically, a first host material including a hole transport material is used in the second color light-emitting layer 144, the highest occupied orbital energy level (HOMO energy level) of the hole transport material is deeper, the HOMO energy level of the doping material is shallower, the hole transport material functions as a trap, and the speed of hole transport is reduced, so that electrons are transported to the junction between the first color light-emitting layer 143 and the second color light-emitting layer 144 and then are recombined with holes.

4. The energy level difference between the hole transport material and the doping material is in the range of 0.2eV to 0.5eV (inclusive), which can control the hole transport speed to some extent, and thus control the recombination position of electrons and holes in the first light emitting unit 140. The situation that holes are difficult to enter the second color light-emitting layer 144 and are difficult to be combined with electrons due to too large energy level difference can be avoided to a certain extent, the recombination effectiveness of the electrons and the holes can be increased, the light-emitting efficiency of the first light-emitting unit 140 can be improved, the light-emitting efficiency of at least one of the first color light-emitting layer 143 and the second color light-emitting layer 144 can be improved, and the power consumption of the light-emitting device 100 can be reduced.

5. The second color light emitting layer 144 uses a mixed host material of a first host material and a second host material, and the dopant material is a guest material or a light emitting material, and is doped in the mixed host material. By mixing the material having the electron-transporting property and the material having the hole-transporting property, a carrier recombination region is increased as compared with a single host material, and at the same time, a role of diluting excitons can be played, so that the efficiency and the lifetime of the light-emitting device 100 can be improved.

In the description of the present application, the directions or positional relationships indicated by the words "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like are for convenience of description or simplicity of describing the embodiments of the present application based on the exemplary directions or positional relationships shown in the drawings, and do not indicate or imply that the devices or components referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, are not to be construed as limiting the present application.

The terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless otherwise specified.

In the description of the present application, it should be noted that, unless otherwise explicitly stated or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, a fixed connection, a detachable connection, or an integral connection; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.

The particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

The foregoing is only a part of the embodiments of the present application, and it should be noted that it is within the scope of the embodiments of the present application that other similar implementation means based on the technical idea of the present application can be adopted by those skilled in the art without departing from the technical idea of the present application.

Claims

1. A light emitting device includes a first electrode, a first light emitting unit, and a second electrode which are stacked;

each film layer between the first electrode and the second electrode forms an optical cavity for transmitting light of a design wavelength from the first electrode or the second electrode;

the second color light-emitting layer comprises a first host material and a doping material; the first host material includes a hole transport material having a highest occupied molecular orbital level less than a highest occupied molecular orbital level of the dopant material.

2. The light-emitting device according to claim 1, wherein an energy level difference between a highest occupied molecular orbital level of the hole transport material and a highest occupied molecular orbital level of the dopant material is not less than 0.2eV and not more than 0.5eV.

3. A light emitting device according to claim 2, wherein the second color light emitting layer further comprises a second host material comprising an electron transporting material;

4. The light emitting device of claim 1, comprising at least one of:

the thickness of the optical cavity is proportional to the design wavelength;

5. The light-emitting device according to claim 1, wherein the design wavelength is not more than 577nm and not less than 492 nm.

6. The light-emitting device according to claim 1, wherein the first electrode is an anode and the second electrode is a cathode;

7. The light-emitting device according to claim 1, further comprising:

the first color light-emitting layer is a red light-emitting layer, and the second color light-emitting layer is a green light-emitting layer.

8. A display panel, comprising: a light emitting device as claimed in any one of claims 1 to 7.

9. The display panel according to claim 8, further comprising: and the color filter is positioned on the light-emitting side of the light-emitting device.

10. A display device, comprising: a display panel as claimed in any one of claims 8-9.