Display panel and display device

Abstract

The application discloses a display panel and a display device. The display panel comprises a plurality of light emitting devices, and the light emitting devices comprise a first light emitting device, a second light emitting device and a third light emitting device. When the brightness is less than a first preset brightness, under a first preset gray scale, the normalized light emitting efficiency of the first light emitting device is greater than a first normalized light emitting efficiency, the normalized light emitting efficiency of the second light emitting device is greater than a second normalized light emitting efficiency, and / or the normalized light emitting efficiency of the third light emitting device is less than a third normalized light emitting efficiency. When the brightness is greater than the first preset brightness, under the first preset gray scale, the normalized light emitting efficiency of the first light emitting device is less than the first normalized light emitting efficiency, the normalized light emitting efficiency of the second light emitting device is less than the second normalized light emitting efficiency, and / or the normalized light emitting efficiency of the third light emitting device is greater than the third normalized light emitting efficiency. The above scheme improves the color deviation problem of the prior art under different ambient brightness.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of display, in particular to a display panel and a display device. BACKGROUND

[0002] With the rapid development of science and technology, display media has become an important part of people's life. Organic light emitting diode (OLED) display media has excellent color and picture quality due to its self-luminous nature. OLED display panel is composed of three primary colors RGB (red, green and blue) array sub-pixels, and different colorimetric values are displayed by controlling the luminous intensity of RGB light emitting devices.

[0003] The existing display panel supplies high current in bright environment and low current in dark environment, so that the luminous intensity of the display panel is adapted to the ambient light intensity. However, due to the inconsistent luminous efficiency and luminance decay of RGB three light emitting devices under different current driving, the luminance of the three light emitting devices under different currents is prone to deviation, which causes color deviation of the white picture formed by the combination of three colors of light, resulting in visual effect of color deviation of the display panel under different ambient brightness. SUMMARY

[0004] The technical problem solved by the present application is to provide a display panel and a display device to improve color deviation.

[0005] To solve the above technical problems, one technical solution adopted by the present application is to provide a display panel, comprising a plurality of light emitting devices, wherein the plurality of light emitting devices comprises a first light emitting device, a second light emitting device and a third light emitting device; under a first preset luminance and a first preset gray scale, the first light emitting device has a first normalized luminous efficiency, the second light emitting device has a second normalized luminous efficiency, and the third light emitting device has a third normalized luminous efficiency; when the luminance is less than the first preset luminance, under the first preset gray scale, the normalized luminous efficiency of the first light emitting device is greater than the first normalized luminous efficiency, the normalized luminous efficiency of the second light emitting device is greater than the second normalized luminous efficiency, and / or the normalized luminous efficiency of the third light emitting device is less than the third normalized luminous efficiency; when the luminance is greater than the first preset luminance, under the first preset gray scale, the normalized luminous efficiency of the first light emitting device is less than the first normalized luminous efficiency, the normalized luminous efficiency of the second light emitting device is less than the second normalized luminous efficiency, and / or the normalized luminous efficiency of the third light emitting device is greater than the third normalized luminous efficiency.

[0006] To solve the above technical problems, another technical solution adopted by the present application is to provide a display device comprising the display panel described in any of the embodiments in the specification.

[0007] The beneficial effects of the present application are that, unlike the prior art, the display panel and the display device of the present application optimize the normalized luminous efficiency of the light-emitting device, so that the blue light-emitting device has a lower luminous brightness than the preset value at a low current density compared to the green light-emitting device and the red light-emitting device, so that the white picture of the display panel at a low current density, i.e. at a low gray scale, is biased towards yellow; at the same time, the red light-emitting device has a lower luminous brightness than the preset value at a high current density compared to the green light-emitting device and the blue light-emitting device, so that the white picture of the display panel at a high current density, i.e. at a high gray scale, is biased towards cyan. Since the human eye is most sensitive to yellow light in a bright environment and most sensitive to green light in a dark environment, and the existing display panel usually supplies high current in bright environment and low current in dark state environment to adapt the luminous brightness of the display panel to the ambient brightness, the above technical solution improves the color deviation problem of the display panel under different ambient brightness. In addition, the display panel made by the technical solution of the present application only needs to perform one-point white picture calibration when it is shipped, which speeds up the production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is a structural schematic diagram of an embodiment of the display panel of the present application;

[0009] Figure 2 is a normalized luminous efficiency-current density diagram of an embodiment of the three light-emitting devices of the present application;

[0010] Figure 3 is a structural schematic diagram of an embodiment of the blue light-emitting device of the present application;

[0011] Figure 4 is a structural schematic diagram of an embodiment of the red light-emitting device of the present application;

[0012] Figure 5 is a color deviation schematic diagram of the display panel of the present application at different gray scales. DETAILED DESCRIPTION

[0013] To make the purpose, technical solutions and effects of the present application clearer and more explicit, the present application is further described in detail below with reference to the drawings and examples. Obviously, the described examples are only part of the examples of the present application, not all examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0014] Referring to Figure 1 , Figure 1 is a structural schematic diagram of an embodiment of the display panel of the present application. The display panel comprises a plurality of light emitting devices, including a first light emitting device, a green light emitting device and a blue light emitting device. In the embodiment of the present application, the first light emitting device is a red light emitting device 1, the second light emitting device is a green light emitting device 2, and the third light emitting device is a blue light emitting device 3. In other embodiments of the present application, the light emitting colors of the light emitting devices can be adjusted according to actual needs.

[0015] On the basis of an OLED display panel, the display panel comprises R, G and B three kinds of sub-pixels, wherein the R sub-pixel emits red light through the red light emitting device 1, the G sub-pixel emits green light through the green light emitting device 2, and the B sub-pixel emits blue light through the blue light emitting device 3. Since any light can be mixed by red, green and blue light in different proportions, and the three kinds of sub-pixels in the OLED display panel can emit light individually, by changing the light emitting brightness of each sub-pixel, the combined color can present the color we need to display. To achieve different light emitting brightness, different current density or current intensity is supplied to each sub-pixel, and the stronger the current density or current intensity, the higher the light emitting brightness, i.e. in a higher gray scale. The pixel is divided into 256 gray scales, among which 0-32 can be set as low gray scale, 33-127 as medium gray scale, and 128-255 as high gray scale. The display panel in the prior art can use an optical sensor to sense the ambient brightness of the outside environment, and adjust the gray scale of the pixel. For example, under the high ambient brightness (illuminance of 1000-10000 lux) of the outdoor in the daytime, the pixel of the display panel is in high gray scale, under the medium ambient brightness (illuminance of 100-500 lux) of the indoor, the pixel of the display panel is in medium gray scale, and under the low ambient brightness (illuminance of 0.02-0.3 lux) of the night, the pixel of the display panel is in low gray scale.

[0016] However, the three kinds of R, G and B sub-pixels may present inconsistent brightness attenuation under the driving of different currents, so that the white picture formed by mixing the three kinds of sub-pixels under the driving of different currents will have color deviation problem, which is due to the different light emitting efficiency of each color sub-pixel under different current intensity or current density, and the different sensitivity of the human eye to different colors of light under different ambient brightness. For example, when the light emitting efficiency of the blue light emitting device 3 is low, or the light emitting efficiency of the red light emitting device 1 and the green light emitting device 2 is high, and the human eye is most sensitive to yellow light under high brightness environment, the visual effect of the displayed white picture is yellowish; and when the light emitting efficiency of the red light emitting device 1 is low, or the light emitting efficiency of the blue light emitting device 3 and the green light emitting device 2 is high, and the human eye is most sensitive to green light under low brightness environment, the visual effect of the displayed white picture is greenish.

[0017] The existing display panel sets the specific luminance of the three sub-pixels under a white picture before leaving the factory to synthesize a suitable white picture, and the specific luminance of the sub-pixels of different display panels is different. The specific setting method is that, under a first preset luminance (for example, 500 nit) and a first preset gray scale (for example, 255 gray scale), the luminance of the red light emitting device 1, the green light emitting device 2 and the blue light emitting device 3 reaches a preset value respectively, and the current or current density required for each light emitting device to reach the preset luminance at this time is written into the chip.

[0018] It should be noted that, due to the large difference in absolute luminous efficiency of the three light emitting devices, in order to increase the comparability of the luminous efficiency of the three light emitting devices, the luminous efficiency of the three light emitting devices is normalized in the present application, and the normalized luminous efficiency η formed can be compared within the same interval, wherein the normalized luminous efficiency is the ratio of the actual luminous efficiency to the maximum luminous efficiency.

[0019] Specifically, under the first preset luminance (for example, 500 nit) and the first preset gray scale (for example, 255 gray scale), the red light emitting device 1 has a first normalized luminous efficiency η R1 , the green light emitting device 2 has a second normalized luminous efficiency η G1 , and the blue light emitting device 3 has a third normalized luminous efficiency η B1 .

[0020] When the luminance is less than the first preset luminance (for example, 200 nit), under the first preset gray scale, the normalized luminous efficiency η R of the red light emitting device 1 is greater than the first normalized luminous efficiency η R1 , and the normalized luminous efficiency η G of the green light emitting device 2 is greater than the second normalized luminous efficiency η G1 , and / or, the normalized luminous efficiency η B of the blue light emitting device 3 is less than the third normalized luminous efficiency η B1 .

[0021] When the luminance is greater than the first preset luminance (for example, 800 nit), under the first preset gray scale, the normalized luminous efficiency η R of the red light emitting device 1 is less than the first normalized luminous efficiency η R1 , and the normalized luminous efficiency η G of the green light emitting device 2 is less than the second normalized luminous efficiency η G1 , and / or, the normalized luminous efficiency η B of the blue light emitting device 3 is greater than the third normalized luminous efficiency η B1 .

[0022] The first preset brightness can be set to the luminance of the white screen in a medium-brightness environment. When the brightness is less than the first preset brightness, the normalized luminous efficiency of blue light is less than the preset normalized luminous efficiency, or the normalized luminous efficiency of red and green light is greater than the preset value. Of course, both of the above conditions can exist simultaneously. In this case, the proportion of blue light in the white screen's luminance decreases, and the resulting white screen appears yellowish. When the brightness is greater than the first preset brightness, the normalized luminous efficiency of blue light is greater than the preset normalized luminous efficiency, or the normalized luminous efficiency of red and green light is less than the preset value. Of course, both of the above conditions can exist simultaneously. In this case, the proportion of blue light in the white screen increases, and the resulting white screen appears bluish. Furthermore, since the most harmful part of the light emitted by the display panel is blue light with a wavelength of 420-440 nm, which can cause irreversible damage to the human retina, a yellowish tint in low-brightness environments can reduce the damage of blue light to the human eye.

[0023] Furthermore, the display panel manufactured using the technical solution of this application only requires white screen bonding at one point during factory production (i.e., setting the brightness of the three light-emitting devices under the first preset brightness and the first preset grayscale), which speeds up production efficiency.

[0024] Optionally, a luminous efficiency attenuation amplitude γ at a certain brightness is also defined. The luminous efficiency attenuation amplitude γ is the ratio of the difference between the normalized luminous efficiency η1 of the same light-emitting device at that brightness and at the first preset brightness to the normalized luminous efficiency η1 at the first preset brightness, i.e., γ = (η - η1) / η1.

[0025] When the brightness is less than the first preset brightness, the luminous efficiency attenuation γ of the blue light-emitting device 3 at the first preset gray level is... B (i.e. (η) B -η B1 ) / η B1 The luminous efficiency attenuation γ of green light-emitting device 2 and red light-emitting device 1 is less than that of green light-emitting device 2 and red light-emitting device 1. G / γ R That is, as the brightness decreases, the normalized luminous efficiency of the blue light-emitting device 3 decreases more than that of the green light-emitting device 2 and the red light-emitting device 1, or increases less than that of the green light-emitting device 2 and the red light-emitting device 1. Therefore, as the brightness decreases, the white screen gradually shifts towards yellow.

[0026] Furthermore, when the brightness is less than the first preset brightness, at the first preset grayscale, the luminous efficiency attenuation of the green light-emitting device 2 is less than that of the red light-emitting device 1, i.e., γ B <γ G <γ RUnder these conditions, the white screen displays a better yellowish tone.

[0027] Optionally, when the brightness is greater than the first preset brightness, the luminous efficiency attenuation γ of the blue light-emitting device 3 at the first preset gray level is... B (i.e. (η) B -η B1 ) / η B1 The luminous efficiency attenuation γ of green light-emitting device 2 and red light-emitting device 1 is greater than that of green light-emitting device 2 and red light-emitting device 1. G / γ R That is, as the brightness increases, the normalized luminous efficiency of the blue light-emitting device 3 decreases less than that of the green light-emitting device 2 and the red light-emitting device 1, or increases more than that of the green light-emitting device 2 and the red light-emitting device 1. Therefore, as the brightness increases, the white screen gradually shifts towards cyan.

[0028] Furthermore, when the brightness is greater than the first preset brightness, the luminous efficiency attenuation γ of the blue light-emitting device 3 at the first preset gray level... B ≥1, meaning that as the brightness increases, the normalized luminous efficiency of the blue light-emitting device 3 actually increases, thus resulting in a bluish effect on the white screen.

[0029] Furthermore, when the brightness is greater than the first preset brightness, at the first preset grayscale, the luminous efficiency attenuation of the green light-emitting device 2 is greater than that of the red light-emitting device 1, i.e., γ B >γ G >γ R Under these conditions, the white screen displays a better yellowish tone.

[0030] See Figure 2 , Figure 2 The normalized luminous efficiency (NEP) trends (L1, L2, L3) of red light-emitting device 1, green light-emitting device 2, and blue light-emitting device 3 under different current densities are plotted. Specifically, as the current density increases, the NEP of red light-emitting device 1 gradually decreases, the NEP of green light-emitting device 2 gradually increases and then gradually decreases, and the NEP of blue light-emitting device 3 gradually increases and then gradually decreases. Since current density is positively correlated with brightness, when the current density is 1 J, i.e., at a lower brightness, NEP... R >η G >η B , and γ B <γ G <γ R When the current density is 15J, i.e. at higher brightness, η R <η G <η B , and γB >γ G >γ R .

[0031] It should be noted that, Figure 2 Only one of the normalized luminous efficiency trends is drawn, and the comparison value between the normalized luminous efficiencies of different light emitting devices does not play an absolute role. In actual setting of the normalized luminous efficiency, the normalized luminous efficiency value at the first preset brightness and the first preset gray scale and the size of the luminous efficiency decay amplitude should be referred to.

[0032] Optionally, referring to Figure 3 , Figure 3 is a structural schematic diagram of an embodiment of the blue light emitting device 3 of the present application. The first highest occupied molecular orbital (HOMO) energy level barrier ΔE between the electron blocking layer (EBL) 33 and the light emitting layer (EML) 34 of the blue light emitting device 3 is greater than 0.3 eV.

[0033] As Figure 3 shown, the blue light emitting device 3 includes a third hole injection layer (HIL) 31, a third hole transport layer (HTL) 32, a third electron blocking layer (EBL) 33, a third light emitting layer (EML) 34, a third hole blocking layer (HBL) 35, a third electron transport layer (ETL) 36, and a third electron injection layer (EIL) 37 which are sequentially stacked. The light emitting principle of the OLED display panel is that electrons are injected from the cathode into the third electron injection layer 37, then sequentially pass through the third electron transport layer 36 and the third hole blocking layer 35 into the third light emitting layer 34, and holes are injected from the anode into the third hole injection layer 31, then sequentially pass through the third hole transport layer 32 and the third electron blocking layer 33 into the third light emitting layer 34. Electrons and holes recombine in the third light emitting layer 34 to form an excited state, and finally the excited state decays to emit light.

[0034] In order to reduce the hole injection at low current density, when the first highest occupied molecular orbital (HOMO) energy level barrier ΔE between the third electron blocking layer 33 and the third light emitting layer 34 of the blue light emitting device 3 is greater than 0.3 eV, the number of hole injection decreases, so that the number of recombination of electrons and holes in the third light emitting layer 34 at low current density decreases, thereby reducing the luminous efficiency of the blue light emitting device 3 at low gray scale.

[0035] Optionally, the hole mobility of the third electron blocking layer 33 of the blue light emitting device 3 is between 10 -7 cm 2 / VS-10 - 6 cm 2 / VS. As the current density increases, the influence of the energy level barrier ΔE between the third electron blocking layer 33 and the third luminescent layer 34 on the luminous efficiency gradually decreases. Therefore, by setting the hole mobility of the third electron blocking layer 33 to between 10 and 10, the efficiency can be improved. -7 -10 - 6 cm 2 / VS, thereby increasing the luminous efficiency of the blue light-emitting device 3 at high grayscale.

[0036] Optionally, see Figure 4 , Figure 4 This is a schematic diagram of one embodiment of the red light-emitting device 1 of this application. The first highest occupied molecular orbital (HOMO) energy level barrier ΔE between the first electron blocking layer (EBL) 13 and the first light-emitting layer (EML) 14 of the red light-emitting device 1 is less than 0.3 eV.

[0037] like Figure 4 As shown, the red light-emitting device 1 includes a first hole injection layer (HIL) 11, a first hole transport layer (HTL) 12, a first electron blocking layer (EBL) 13, a first light-emitting layer (EML) 14, a first hole blocking layer (HBL) 15, a first electron transport layer (ETL) 16 and a first electron injection layer (EIL) 17 stacked sequentially. The first light-emitting layer 14 includes a P-Host light-emitting host material layer (P-Host) 141 and an N-Host light-emitting host material layer (N-Host) 142 stacked sequentially. The P-Host light-emitting host material layer 141 is disposed close to the first electron blocking layer 13.

[0038] To increase hole injection at low current densities, when the second highest occupied molecular orbital (HOMO) energy level barrier ΔE between the first electron blocking layer 13 and the P-polar light-emitting host material layer 141 in the first light-emitting layer 14 of the red light-emitting device 1 is less than 0.3 eV, the number of holes injected increases, which increases the recombination of electrons and holes in the first light-emitting layer 14 at low current densities, thereby increasing the luminous efficiency of the red light-emitting device 1 at low gray levels.

[0039] Optionally, the hole mobility of the first electron blocking layer 13 of the red light emitting device 1 is between 10 and 10. -7 cm 2 / VS-10 - 5 cm 2 / VS. As the current density increases, the influence of the energy level barrier ΔE between the first electron blocking layer 13 and the first light-emitting layer 14 on the luminous efficiency gradually decreases. Therefore, by setting the hole mobility of the first electron blocking layer 13 to between 10 and 14, the luminous efficiency can be improved. -7 cm 2 / VS-10 -5 cm2 / VS, thereby reducing the luminous efficiency of the red light emitting device 1 at high gray levels.

[0040] The improvements of the red light emitting device 1 and the blue light emitting device 3 can be made simultaneously or separately.

[0041] Changing the hole mobility of the electron blocking layer can be achieved by various means, such as changing the material of the electron blocking layer, changing the thickness or structure of the electron blocking layer, etc. The above means are all prior art and will not be described here.

[0042] Referring to Figure 5 , Figure 5 is a color deviation diagram of the display panel of the present application at different gray levels. Figure 5 The position of the white picture of the display panel of the present application at different gray levels in the chromaticity coordinate is illustrated, from which Figure 5 It can be seen that as the gray level gradually increases, the white picture of the display panel gradually moves from the vicinity of the cyan region (i.e. visual effect is cyan) to the vicinity of the yellow region (i.e. visual effect is yellow). For example, when the low gray level is 32, the white picture of the display panel is closest to the cyan region, and the white picture presents a visual effect of cyan. When the high gray level is 196 or 255, the white picture of the display panel is close to the yellow region, and the white picture presents a visual effect of yellow, and the higher the gray level, the higher the degree of yellow.

[0043] The embodiments of the present application also provide a display device comprising the display panel in any of the foregoing embodiments, and the display device can be a mobile phone, a tablet computer, a smart watch, a wearable device, or other electronic display products.

[0044] The above is only an embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation using the content of the specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A display panel, characterized in that, include: Multiple light-emitting devices, including red light-emitting devices, green light-emitting devices, and blue light-emitting devices; Under a first preset brightness and a first preset grayscale, the red light-emitting device has a first normalized luminous efficiency, the green light-emitting device has a second normalized luminous efficiency, and the blue light-emitting device has a third normalized luminous efficiency. When the brightness is less than the first preset brightness, under the first preset grayscale, the normalized luminous efficiency of the red light-emitting device is greater than the first normalized luminous efficiency and the normalized luminous efficiency of the green light-emitting device is greater than the second normalized luminous efficiency, and / or, the normalized luminous efficiency of the blue light-emitting device is less than the third normalized luminous efficiency. When the brightness is greater than the first preset brightness, under the first preset grayscale, the normalized luminous efficiency of the red light-emitting device is less than the first normalized luminous efficiency and the normalized luminous efficiency of the green light-emitting device is less than the second normalized luminous efficiency, and / or, the normalized luminous efficiency of the blue light-emitting device is greater than the third normalized luminous efficiency. The first highest occupied molecular orbital energy level barrier between the electron blocking layer and the light-emitting layer of the blue light-emitting device is greater than 0.3 eV.

2. The display panel according to claim 1, characterized in that, A luminous efficiency decay range is defined, which is the ratio of the difference between the normalized luminous efficiency at this brightness and at the first preset brightness to the normalized luminous efficiency at the first preset brightness. When the brightness is less than the first preset brightness, under the first preset grayscale, the luminous efficiency attenuation of the blue light-emitting device is less than that of the green and red light-emitting devices.

3. The display panel according to claim 2, characterized in that, When the brightness is less than the first preset brightness, under the first preset grayscale, the luminous efficiency attenuation of the green light-emitting device is less than that of the red light-emitting device.

4. The display panel according to claim 2, characterized in that, When the brightness is greater than the first preset brightness, under the first preset gray level, the luminous efficiency attenuation of the blue light-emitting device is greater than that of the green and red light-emitting devices.

5. The display panel according to claim 4, characterized in that, When the brightness is greater than the first preset brightness, the luminous efficiency attenuation of the blue light-emitting device is greater than or equal to 1 at the first preset gray level.

6. The display panel according to claim 2, characterized in that, When the brightness is greater than the first preset brightness, under the first preset grayscale, the luminous efficiency attenuation of the green light-emitting device is greater than that of the red light-emitting device.

7. The display panel according to claim 1, characterized in that, The hole mobility of the electron blocking layer of the blue light-emitting device is between 10. -7 cm 2 / VS -10 -6 cm 2 / VS.

8. The display panel according to claim 1, characterized in that, The second highest occupied molecular orbital energy level barrier between the electron blocking layer and the emitting layer of the red light-emitting device is less than 0.3 eV.

9. The display panel according to claim 1, characterized in that, The hole mobility of the electron blocking layer of the red light-emitting device is between 10. -7 cm 2 / VS -10 -5 cm 2 / VS.

10. A display device, characterized in that, The display panel includes any one of claims 1-9.

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