Light-emitting device and display panel

Abstract

The present disclosure provides a light-emitting device and a display panel, and belongs to the technical field of display. The light-emitting device comprises a cathode, a light-emitting functional layer and an anode which are arranged in a stack. The light-emitting functional layer comprises a light-emitting layer group, a charge generation layer and a third light-emitting layer which are arranged in a stack. The light-emitting layer group comprises a first light-emitting layer and a second light-emitting layer which are arranged in a stack. The first light-emitting layer and the second light-emitting layer have different colors of emitted light. The first light-emitting layer comprises a plurality of sub light-emitting layers which are arranged in a stack. In the plurality of sub light-emitting layers, the highest occupied molecular orbital energy level of the host material of the sub light-emitting layer close to the anode side is the highest.

Description

Technical Field

[0001] This disclosure relates to the field of display technology, and in particular to a light-emitting device and a display panel. Background Technology

[0002] In common multilayer device architectures, white OLED devices are typically combined with color filters to achieve different colors of light output. However, current multilayer devices suffer from color shift due to voltage variations. Summary of the Invention

[0003] Based on the background art, this disclosure presents a light-emitting device and a display panel.

[0004] In a first aspect, this disclosure provides a light-emitting device, comprising a cathode, a light-emitting functional layer, and an anode stacked together; wherein the light-emitting functional layer comprises a group of light-emitting layers, a charge-generating layer, and a third light-emitting layer stacked together; The light-emitting layer group includes a first light-emitting layer and a second light-emitting layer stacked together, wherein the first light-emitting layer and the second light-emitting layer emit light of different colors; The first light-emitting layer includes multiple sub-light-emitting layers stacked together. Among the multiple sub-light-emitting layers, the highest occupied molecular orbital energy level of the main material of the sub-light-emitting layer closest to the anode side is the highest.

[0005] Optionally, in the direction from the first light-emitting layer to the second light-emitting layer, the highest occupied molecular orbital energy levels of the host materials of the plurality of sub-light-emitting layers decrease sequentially.

[0006] Optionally, in the plurality of sub-light-emitting layers, the difference in the highest occupied molecular orbital energy level of the host material of two adjacent sub-light-emitting layers is less than 0.5 eV.

[0007] Optionally, the total thickness of the first light-emitting layer is 50-200 angstroms.

[0008] Optionally, the first light-emitting layer includes a first sub-light-emitting layer close to the anode, and a second sub-light-emitting layer located on the side of the first sub-light-emitting layer opposite to the anode; The thickness ratio of the first sub-light-emitting layer to the second sub-light-emitting layer is 1:4-4:1.

[0009] Optionally, the light-emitting layer group is located near the anode, and in the light-emitting layer group, the second light-emitting layer is located on the side of the first light-emitting layer that is close to the charge-generating layer.

[0010] Optionally, the light-emitting layer group is located close to the cathode, and in the light-emitting layer group, the second light-emitting layer is located on the side of the first light-emitting layer away from the charge-generating layer.

[0011] Optionally, the highest occupied molecular orbital energy level of the host material of at least one of the sub-light-emitting layers is greater than the highest occupied molecular orbital energy level of the host material of the second light-emitting layer.

[0012] Optionally, the highest occupied molecular orbital energy level of the host material of the second light-emitting layer is located between the highest occupied molecular orbital energy levels of the host materials of the plurality of sub-light-emitting layers.

[0013] Optionally, the peak wavelength of the emitted light from the first light-emitting layer is 600-700 nm, the peak wavelength of the emitted light from the second light-emitting layer is 500-600 nm, and the peak wavelength of the emitted light from the third light-emitting layer is 400-500 nm.

[0014] A second aspect of this disclosure provides a display panel, comprising: The light-emitting device as described in the first aspect above.

[0015] The light-emitting device disclosed herein includes a cathode, a light-emitting functional layer, and an anode stacked together; wherein the light-emitting functional layer includes a stacked light-emitting layer group, a charge-generating layer, and a third light-emitting layer; wherein the light-emitting layer group includes a stacked first light-emitting layer and a second light-emitting layer, the first light-emitting layer and the second light-emitting layer emitting light of different colors; wherein the first light-emitting layer includes a plurality of stacked sub-light-emitting layers, and among the plurality of sub-light-emitting layers, the highest occupied molecular orbital energy level of the host material of the sub-light-emitting layer closest to the anode side is the highest; Therefore, this disclosure sets the first light-emitting layer as a multi-layered sub-light-emitting layer. In this multi-layered sub-light-emitting layer, the highest occupied molecular orbital energy level of the host material in the light-emitting layer closest to the anode is the highest. Thus, at low voltage, holes are less likely to cross the sub-light-emitting layer with a lower highest occupied molecular orbital energy level, causing the recombination region of holes and electrons to be closer to the first light-emitting layer. At high voltage, however, the electron migration rate is greater than the hole migration rate, ensuring that the recombination region of holes and electrons remains close to the first light-emitting layer. Consequently, the light intensity ratio of the first and second light-emitting layers is consistent under both high and low voltage conditions. This ensures that the white light emission spectrum of the light-emitting device remains consistent under both high and low voltage conditions, avoiding color shift problems that occur when white light passes through a color filter.

[0016] The above description is merely an overview of the technical solution disclosed herein. In order to better understand the technical means of this disclosure and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this disclosure more apparent and understandable, specific embodiments of this disclosure are described below. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments or related technologies of this disclosure, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. It should be noted that the scale in the drawings is for illustration only and does not represent the actual scale.

[0018] Figure 1 A schematic diagram of the structure of a stacked organic light-emitting device in the related technology is shown; Figure 2 The emission spectrum of a stacked organic light-emitting device in the related art is shown, where a is the emission spectrum of the stacked light-emitting device with a driving voltage of 6.0V, and b is the emission spectrum of the stacked light-emitting device with a driving voltage of 8.5V. Figure 3 The curves showing the variation of the color point of different colors of light with voltage in stacked organic light-emitting devices in related technologies are shown, where a is the curve of the color point of blue light with voltage and b is the curve of the color point of red light with voltage. Figure 4 A schematic diagram of the structure of the light-emitting device provided in an embodiment of this disclosure is shown; Figure 5 The following is an illustration of the emission spectrum of the light-emitting device provided in the embodiments of the present disclosure, wherein a is the emission spectrum of the stacked light-emitting device when the driving voltage is 6.0V, and b is the emission spectrum of the stacked light-emitting device when the driving voltage is 8.5V; Figure 6 The diagram shows the color point curves of different colors of light in the light-emitting device provided in the embodiments of this disclosure as a function of voltage, where a is the color point curve of blue light as a function of voltage and b is the color point curve of red light as a function of voltage. Figure 7 It shows Figure 4 The diagram shows the carrier migration direction in the light-emitting device. Figure 8 A schematic diagram of the structure of a light-emitting device provided in another embodiment of this disclosure is shown; Figure 9 It shows Figure 8 The diagram shows the carrier migration direction in the light-emitting device. Figure 10 A schematic diagram of the structure of a light-emitting device provided in yet another embodiment of this disclosure is shown; Figure 11 A schematic diagram of the highest occupied molecular orbital energy level of the host material of the multi-layer luminescent layer in the luminescent layer group of the present disclosure is shown. Detailed Implementation

[0019] To make the above-mentioned objectives, features, and advantages of this disclosure more apparent and understandable, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0020] Micro OLED (Organic Light-Emitting Diode) displays require ultra-high resolution to meet the demands of small size, lightweight design, and ultra-high definition. To achieve this ultra-high resolution, Micro OLED pixel sizes need to reach the micrometer or even nanometer scale. However, the pixel size of traditional LCD and OLED displays is several times larger than that of Micro OLEDs. Due to the extremely small pixel size and limitations in manufacturing precision, Micro OLEDs cannot easily achieve the RGB three-color arrangement similar to large-size OLEDs. Instead, they use white light-emitting units combined with RGB three-color color filters to achieve full-color display.

[0021] In this context, white light-emitting elements are typically separated into two OLED light-emitting layers, making them 2-Tandem devices. Constructing stacked OLED devices can effectively improve important optoelectronic performance indicators of Micro OLEDs, such as current efficiency, output brightness, and operating life. Introducing a charge-generating layer connected in series with multiple light-emitting layers of different colors can achieve the effect of superimposed light emission.

[0022] In related technologies, Micro OLED display devices generally employ a combination of stacked OLED devices and color filters to form different colors of emitted light. (Referring to...) Figure 1 , Figure 1 A schematic diagram of a common stacked OLED device is shown, such as... Figure 1 As shown, the stacked OLED device includes a light-emitting unit composed of two independent light-emitting layers: a red light-emitting layer (R-EML) and a green light-emitting layer (G-EML).

[0023] In a structure where red and green light-emitting layers are directly stacked, the migration rates of electrons and holes differ under different voltages. The recombination regions of electrons and holes in the red and green light-emitting layers change with voltage, which in turn changes the relative ratio of the luminous intensities of red and green light. This causes the white light emission spectrum to change with voltage. In Micro OLED display devices, this means that after white light passes through the color filter, the color points change with voltage.

[0024] Reference Figure 2 , Figure 2The emission spectra of red, green, and blue light under different voltages are shown. In this diagram, a represents the emission spectra of red, green, and blue light at a voltage of 6.0V, and b represents the emission spectra of red, green, and blue light at a voltage of 8.5V. Figure 2 As shown, the ratio between the luminous intensity of red light and the luminous intensity of green light at 6.0V is different from the ratio at 8.5V; and, referring to... Figure 3 , Figure 3 The diagram shows the curves of blue and red light points changing with voltage in a display device, where 'a' represents the curve of blue light point changing with voltage, and 'b' represents the curve of red light point changing with voltage. Figure 3 As shown, at low voltage, the proportion of green light intensity is relatively high, and the color coordinates of red and blue light are relatively high. At high voltage, the proportion of green light intensity decreases, and the color coordinates of red and blue light decrease.

[0025] In view of this, the present disclosure provides a light-emitting device and a display panel. By setting multiple red light-emitting layers, and the highest occupied molecular orbital energy level of the main material of the red light-emitting layer near the anode in the multiple red light-emitting layers is the highest, this makes it possible for holes to be blocked by the red light-emitting layers with lower highest occupied molecular orbital energy levels in the multiple red light-emitting layers under low voltage, so that electrons and holes recombine in the region near the multiple red light-emitting layers. Under high voltage, the electron migration rate is greater than the hole migration rate, and electrons and holes also recombine in the region near the multiple red light-emitting layers. Therefore, the recombination region of electrons and holes in the light-emitting device changes less with voltage, thereby solving the problem of color point drift with voltage in the display device.

[0026] Reference Figure 4 , Figure 4 A schematic diagram of the structure of the light-emitting device provided in the embodiments of this disclosure is shown, such as... Figure 4 As shown, the light-emitting device includes a cathode 100, a light-emitting functional layer 200, and an anode 300 stacked together; wherein, the light-emitting functional layer 200 includes a light-emitting layer group 201, a charge generating layer 240, and a third light-emitting layer 230 stacked together. The light-emitting layer group 201 includes a first light-emitting layer 210 and a second light-emitting layer 220 stacked together, and the first light-emitting layer 210 and the second light-emitting layer 220 emit light of different colors. The first light-emitting layer 210 includes a plurality of sub-light-emitting layers 211 stacked together. Among the plurality of sub-light-emitting layers 211, the highest occupied molecular orbital energy level of the main material of the sub-light-emitting layer 211 closest to the anode 300 is the highest.

[0027] In this embodiment, the light-emitting device is a stacked light-emitting device, which can be considered as a structure obtained by connecting two independent light-emitting units in series. The two independent light-emitting units are separated by a charge-generating layer 240. The light-emitting layer group 201 includes a stacked first light-emitting layer 210 and a second light-emitting layer 220, that is, the first light-emitting layer 210 and the second light-emitting layer 220 are located in the same light-emitting unit, while the third light-emitting layer 230 is located in a different light-emitting unit from the first light-emitting layer 210 and the second light-emitting layer 220. Specifically, the light-emitting layer group 201 can be a red-green light-emitting layer, while the third light-emitting layer 230 can be a blue light-emitting layer to avoid the quenching effect of the blue light material on the red-green light-emitting material. The stacking order between the two independent light-emitting units is not limited in this embodiment. It can be that the light-emitting unit including the light-emitting layer group 201 is stacked on top of the light-emitting unit including the third light-emitting layer 230, or vice versa.

[0028] The first light-emitting layer 210 includes multiple sub-light-emitting layers 211. The main materials of the multiple sub-light-emitting layers 211 can be different, so that the multiple sub-light-emitting layers 211 have different highest occupied molecular orbital energy levels. Among them, the highest occupied molecular orbital energy level of the main material of the sub-light-emitting layer 211 near the anode 300 is the highest. In this case, holes migrate from the anode 300 to the cathode 100. Since the highest occupied molecular orbital energy level of the main material of the sub-light-emitting layer 211 near the anode 300 is the highest, the difference between it and the highest occupied molecular orbital energy level of the light-emitting functional layer on the anode 300 side is small, which facilitates the migration of holes toward the sub-light-emitting layer 211. However, since the highest occupied molecular orbital energy levels of the main materials of the other sub-light-emitting layers 211 are lower than the highest occupied molecular orbital energy level of the main material of the sub-light-emitting layer 211 near the anode 300, the other sub-light-emitting layers 211 form shallow traps, which can temporarily capture holes and reduce the hole migration rate.

[0029] Therefore, at low voltage, holes are easily confined in the first light-emitting layer 210, causing the recombination region of holes and electrons to be close to the first light-emitting layer 210; while at high voltage, the electron migration rate is higher than the hole migration rate, causing the recombination region of holes and electrons to also be close to the first light-emitting layer 210. Thus, regardless of whether the voltage is high or low, the recombination region of holes and electrons is close to the first light-emitting layer 210, so the light intensity ratio of the first light-emitting layer 210 and the second light-emitting layer 220 does not change much under high and low voltage, thereby solving the problem of color shift caused by voltage change.

[0030] Specifically, the first light-emitting layer 210 may include two, three, or more sub-light-emitting layers 211. When it includes three or more sub-light-emitting layers 211, the highest occupied molecular orbital energy level of the host material of the sub-light-emitting layer 211 closest to the anode 300 is the highest, while the highest occupied molecular orbital energy level of the host material of the other sub-light-emitting layers 211 is lower than that of the host material of the sub-light-emitting layer 211 closest to the anode 300. That is, the highest occupied molecular orbital energy levels of the host materials of the multiple sub-light-emitting layers 211 other than the sub-light-emitting layer 211 closest to the anode 300 are different.

[0031] It is understandable that the light-emitting layer generally includes a host material and a guest material. The host material is responsible for transporting charge carriers, and the guest material is responsible for emitting light. Therefore, the host materials of the multiple sub-light-emitting layers 211 are different, so that the multiple sub-light-emitting layers 211 have different highest occupied molecular orbital energy levels, and the host material of the sub-light-emitting layer closest to the anode 300 has the highest highest occupied molecular orbital energy level. The guest materials of the multiple sub-light-emitting layers 211 can be the same or different, as long as the color of the light emitted by the multiple sub-light-emitting layers 211 is consistent.

[0032] Specifically, the light intensity ratio of the first light-emitting layer 210 and the second light-emitting layer 220 can be adjusted according to the required white light spectrum. Specifically, the thickness of the multiple sub-light-emitting layers 211 in the first light-emitting layer 210 can be adjusted to achieve the adjustment of the light intensity ratio of the two light-emitting layers of different colors. Alternatively, the mass ratio of the main material and the object material in the multiple sub-light-emitting layers 211 in the first light-emitting layer 210 can be adjusted to achieve the adjustment of the light intensity ratio of the two light-emitting layers of different colors.

[0033] In some examples, the light-emitting functional layer 200 may also include auxiliary light-emitting functional layers such as a hole injection layer, a hole transport layer, an electron blocking layer, an electron transport layer, and an electron injection layer. In the stacked light-emitting device, both independent light-emitting units may include hole injection layers, hole transport layers, electron blocking layers, electron transport layers, and electron injection layers. The hole injection layers, hole transport layers, electron blocking layers, electron transport layers, and electron injection layers included in different light-emitting units may vary.

[0034] The light-emitting device provided in this embodiment configures the first light-emitting layer 210 as a multilayer sub-light-emitting layer 211. The highest occupied molecular orbital energy level of the main material of the sub-light-emitting layer 211 near the anode 300 is the highest. Thus, at low voltage, holes are more likely to be retained at the first light-emitting layer 210 because the highest occupied molecular orbital energy level of the main material of the sub-light-emitting layer 211 near the anode 300 is higher than that of the main material of the other sub-light-emitting layers 211. This causes the recombination region of electrons and holes to be close to the first light-emitting layer 210. At high voltage, the electron migration rate is greater than the hole migration rate, causing the recombination region of electrons and holes to be close to the first light-emitting layer 210. Therefore, the recombination region of holes and electrons in the light-emitting layer group 201 does not change much with voltage. Consequently, the light intensity ratio of the first light-emitting layer 210 and the second light-emitting layer 220 does not change much with voltage. Therefore, applying this light-emitting device to an OLED display device can help improve the phenomenon of pixel color point drift caused by voltage changes.

[0035] In one embodiment, in the direction from the first light-emitting layer 210 to the second light-emitting layer 220, the highest occupied molecular orbital energy levels of the host material of the plurality of sub-light-emitting layers 211 decrease sequentially.

[0036] Specifically, the direction from the first emitting layer 210 to the second emitting layer 220 is the hole migration direction. In this direction, the highest occupied molecular orbital energy levels of the host materials of the multiple sub-emitting layers 211 decrease sequentially. This prevents holes from accumulating at the interface of a single sub-emitting layer 211 during hole transport, thereby expanding the recombination region between holes and electrons and improving the stability of the emitted white light spectrum. Taking the first sub-emitting layer 210 as including a first sub-emitting layer 211a, a second sub-emitting layer 211b, and a third sub-emitting layer 211c as an example, in the direction from the first emitting layer 210 to the second sub-emitting layer 220, the highest occupied molecular orbital energy level of the host material of the first sub-emitting layer 211a is higher than that of the host material of the second sub-emitting layer 211b; and the highest occupied molecular orbital energy level of the host material of the second sub-emitting layer 211b is higher than that of the host material of the third sub-emitting layer 211c.

[0037] In the multiple sub-emissive layers 211, the difference in the highest occupied molecular orbital energy level of the host material of any two adjacent sub-emissive layers 211 can be the same or different; regardless of the difference in the highest occupied molecular orbital energy level of the host material of any two adjacent sub-emissive layers 211, the difference in the highest occupied molecular orbital energy level of the host material of any two adjacent sub-emissive layers 211 is less than 0.5 eV.

[0038] Taking the sequential stacking of a first sub-emitting layer 211a, a second sub-emitting layer 211b, and a third sub-emitting layer 211c along the direction from the first emitting layer 210 to the second emitting layer 220 as an example, the energy difference between the highest occupied molecular orbital of the host material of the first sub-emitting layer 211a and the highest occupied molecular orbital of the host material of the second sub-emitting layer 211b can be 0.1 eV; the energy difference between the highest occupied molecular orbital of the host material of the second sub-emitting layer 211b and the highest occupied molecular orbital of the host material of the third sub-emitting layer 211c can be 0.2 eV; or, the energy difference between the highest occupied molecular orbital of the host material of the first sub-emitting layer 211a and the highest occupied molecular orbital of the host material of the second sub-emitting layer 211b can be 0.2 eV; the energy difference between the highest occupied molecular orbital of the host material of the second sub-emitting layer 211b can also be 0.2 eV.

[0039] In one embodiment, the total thickness of the first light-emitting layer 210 is 50-200 angstroms.

[0040] It is important to note that the total thickness of the first light-emitting layer 210 is the sum of the thicknesses of the multiple sub-light-emitting layers 211, and can be specifically set according to the intensity ratio of various colors of light in the white light spectrum. For example, the total thickness of the first light-emitting layer 210 can be 50 angstroms, 100 angstroms, 150 angstroms, or 200 angstroms. Since the first light-emitting layer 210 includes multiple sub-light-emitting layers 211, the thickness of each sub-light-emitting layer 211 can be the same or different, as long as the total thickness of the first light-emitting layer 210 is maintained between 50 and 200 angstroms.

[0041] In one embodiment, continue to refer to Figure 4 The first light-emitting layer 210 includes a first sub-light-emitting layer 211a near the anode 300, and a second sub-light-emitting layer 211b located on the side of the first sub-light-emitting layer 211a away from the anode 300; wherein the thickness ratio of the first sub-light-emitting layer 211a and the second sub-light-emitting layer 211b is 1:4-4:1.

[0042] In this embodiment, the thickness of the first sub-light-emitting layer 211a and the second sub-light-emitting layer 211b can be the same or different. For example, the ratio of the thickness of the first sub-light-emitting layer 211a and the second sub-light-emitting layer 211b can be 1:4, 1:2, 1:1, 2:1, 4:1, etc.

[0043] Among them, light-emitting devices including first sub-light-emitting layers 211a and second sub-light-emitting layers 211b with different thickness ratios were tested, and the results were as follows: Figure 5 and Figure 6In the structure shown, as the thickness of the second sub-emitting layer 211b gradually increases, the light intensity emitted from the first emitting layer 210 gradually increases under both low and high voltage conditions, while the color coordinate shift decreases. Therefore, the thickness of the second sub-emitting layer 211b can be adjusted according to the light intensity requirements of the emitted light, resulting in a smaller color coordinate shift while meeting the light intensity requirements. Figure 5 and Figure 6 Analyzing the results shown, when the first light-emitting layer 210 includes two sub-light-emitting layers 211, the recombination region of holes and electrons includes a portion of the first sub-light-emitting layer 211a, a portion of the second sub-light-emitting layer 211b, and a portion of the second light-emitting layer 220. Adjusting the thickness of the second sub-light-emitting layer 211b can adjust the proportion of the light-emitting material of the first light-emitting layer 210 in the recombination region, thereby adjusting the light intensity of the emitted light from the first light-emitting layer 210. Thus, the light intensity ratio of the emitted light from the first light-emitting layer 210 and the emitted light from the second light-emitting layer 220 can be adjusted.

[0044] Understandably, the intensity of the emitted light from the first light-emitting layer 210 is also related to the ratio of the host material to the guest material in the multilayer sub-light-emitting layer 211. When the proportion of guest material is higher, the intensity of the emitted light from the light-emitting layer is stronger, while when the proportion of guest material is lower, the intensity of the emitted light from the light-emitting layer is lower. Therefore, when forming the multilayer sub-light-emitting layer 211, the thickness of the multilayer sub-light-emitting layer 211 can be adjusted, or the proportion of guest material in the multilayer sub-light-emitting layer 211 can be adjusted; of course, both the thickness and the proportion of guest material in the multilayer sub-light-emitting layer 211 can be adjusted so that the intensity of the emitted light from the first light-emitting layer 210 has a target ratio with the intensity of the emitted light from the second light-emitting layer 210. That is, in the light-emitting device, the multilayer sub-light-emitting layer 211 can have different thicknesses, different proportions of guest material, or both.

[0045] In this disclosure, the stacked light-emitting device includes two light-emitting units connected in series. The stacking order of the two light-emitting units is not limited. For example, the light-emitting unit including the light-emitting layer group 201 can be close to the anode 300, or the light-emitting unit including the third light-emitting layer 230 can be close to the anode 300. In both cases, the first light-emitting layer 210 and the second light-emitting layer 220 in the light-emitting layer group 201 are arranged in the direction from the anode 300 to the cathode 100 to facilitate hole injection into the first light-emitting layer 210 and electron injection into the second light-emitting layer 220.

[0046] In one example, continue to refer to Figure 4 The light-emitting layer group 201 is close to the anode 300, and in the light-emitting layer group 201, the second light-emitting layer 220 is located on the side of the first light-emitting layer 210 close to the charge generation layer 240.

[0047] In this embodiment, from the anode 300 to the cathode 100, the light-emitting functional layer 200 sequentially includes a first light-emitting layer 210, a second light-emitting layer 220, a charge-generating layer 240, and a third light-emitting layer 230. The first light-emitting layer 210 includes a first sub-light-emitting layer 211a and a second sub-light-emitting layer 211b. The highest occupied molecular orbital energy level of the host material of the first sub-light-emitting layer 211a is higher than the highest occupied molecular orbital energy level of the host material of the second sub-light-emitting layer 211b.

[0048] When the light-emitting device is stacked in the order of the first light-emitting layer 210, the second light-emitting layer 220, the charge-generating layer 240, and the third light-emitting layer 230, refer to Figure 7 , Figure 7 This diagram illustrates the migration direction of charge carriers in the light-emitting device in this embodiment. Figure 7 As shown, under low voltage, the migration rate of holes is higher than that of electrons. At this time, holes are injected from auxiliary layers such as the hole injection layer into the first sub-emissive layer 211a. Because the highest occupied molecular orbital energy level of the host material of the first sub-emissive layer 211a is higher than that of the host material of the second sub-emissive layer 211b, some holes are temporarily trapped in the first sub-emissive layer 211a, while other holes migrate to the second sub-emissive layer 211b and the second emissive layer 220. Meanwhile, electrons are injected from the charge generation layer 240 and sequentially migrate to the second emissive layer 220. In the second sub-emissive layer 211b and the first sub-emissive layer 211a, the recombination region of electrons and holes is biased towards the first emissive layer 210. Under high voltage, the migration rate of electrons is higher than that of holes, so electrons gradually migrate from the charge generation layer 240 to the second emissive layer 220, the second sub-emissive layer 211b and the first sub-emissive layer 211a. Under high voltage, it is easier for holes to migrate from the first sub-emissive layer 211a, which has a higher energy level of the highest occupied molecular orbital, to the second sub-emissive layer 211b, so that the recombination region of electrons and holes is biased towards the first emissive layer 210.

[0049] In another example, refer to Figure 8 , Figure 8 A schematic diagram of the structure of a light-emitting device provided in another embodiment of this disclosure is shown, as follows: Figure 8 As shown, the light-emitting layer group 201 is close to the cathode 100, and in the light-emitting layer group 201, the second light-emitting layer 220 is located on the side of the first light-emitting layer 210 away from the charge-generating layer 240.

[0050] In this embodiment, from the anode 300 to the cathode 100, the light-emitting functional layer 200 includes a third light-emitting layer 230, a charge-generating layer 240, a first light-emitting layer 210, and a second light-emitting layer 220; the first light-emitting layer 210 includes a first sub-light-emitting layer 211a and a second sub-light-emitting layer 211b, and the highest occupied molecular orbital energy level of the host material of the first sub-light-emitting layer 211a is higher than the highest occupied molecular orbital energy level of the host material of the second sub-light-emitting layer 211b.

[0051] When the light-emitting device is stacked in the order of the third light-emitting layer 230, the charge-generating layer 240, the first light-emitting layer 210, and the second light-emitting layer 220, refer to Figure 9 , Figure 9 It shows Figure 8 The schematic diagram of the carrier migration direction of the light-emitting device shown is as follows: Figure 9 As shown, under low voltage, the migration rate of holes is higher than that of electrons. At this time, holes are injected from the charge generation layer 240 into the first sub-emissive layer 211a. Because the highest occupied molecular orbital energy level of the host material of the first sub-emissive layer 211a is higher than that of the host material of the second sub-emissive layer 211b, some holes are temporarily trapped in the first sub-emissive layer 211a, while others migrate to the second sub-emissive layer 211b and the second emissive layer 220. Meanwhile, electrons are injected from the cathode 100 and sequentially migrate to the second emissive layer 220. In the second sub-emissive layer 211b and the first sub-emissive layer 211a, the recombination region of electrons and holes is biased towards the first emissive layer 210. Under high voltage, the migration rate of electrons is higher than that of holes, so electrons gradually migrate from the cathode 100 to the second emissive layer 220, the second sub-emissive layer 211b, and the first sub-emissive layer 211a. Under high voltage, it is easier for holes to migrate from the first sub-emissive layer 211a, which has a higher energy level of the highest occupied molecular orbital, to the second sub-emissive layer 211b, so the recombination region of electrons and holes is biased towards the first emissive layer 210.

[0052] Understandably, in the light-emitting layer group 201, the highest occupied molecular orbital energy level of the host material of at least one sub-light-emitting layer 211 in the first light-emitting layer 210 is higher than that of the host material of the second light-emitting layer 220. Since the highest occupied molecular orbital energy level of the host material of the sub-light-emitting layer 211 closest to the anode 300 is the highest, it can be considered that the highest occupied molecular orbital energy level of the host material of the sub-light-emitting layer 211 closest to the anode 300 is higher than that of the host material of the second light-emitting layer 220. This ensures that holes injected into the sub-light-emitting layer 211 can migrate to the second light-emitting layer 220. For other sub-light-emitting layers 211, the highest occupied molecular orbital energy level of their host material can be higher or lower than that of the host material of the second light-emitting layer 220.

[0053] In one embodiment, the highest occupied molecular orbital energy level of the host material of the second light-emitting layer 220 is located between the highest occupied molecular orbital energy levels of the host materials of the plurality of sub-light-emitting layers 211.

[0054] In this embodiment, even when the highest occupied molecular orbital energy level of the main material of the second light-emitting layer 220 is located between the highest occupied molecular orbital energy levels of the main materials of the multiple sub-light-emitting layers 211, it is still possible to satisfy the migration of holes injected into the first light-emitting layer 210 toward the second light-emitting layer 220. However, since the highest occupied molecular orbital energy level of the main material of some sub-light-emitting layers 211 is lower than that of the main material of the second light-emitting layer, it is more difficult for holes to migrate from the first light-emitting layer 210 to the second light-emitting layer 220 under low voltage. Consequently, the recombination region of holes and electrons is closer to the first light-emitting layer 210. Thus, the recombination region of holes and electrons under low voltage is closer to the recombination region of holes and electrons under high voltage. This makes the light intensity ratio of the first light-emitting layer 210 and the second light-emitting layer 220 under low voltage deviate less from the light intensity ratio of the first light-emitting layer 210 and the second light-emitting layer 220 under high voltage, thereby improving the phenomenon of color point drift in the display device with voltage changes.

[0055] In any of the above embodiments, the first light-emitting layer 210 is a red light-emitting layer, the second light-emitting layer 220 is a green light-emitting layer, and the third light-emitting layer 230 is a blue light-emitting layer.

[0056] It is understandable that blue light materials have a shorter lifespan compared to red and green light materials, and blue light materials have a larger band gap. Therefore, setting a separate light-emitting layer for blue light materials can put them in a relatively independent carrier environment, making it easier to regulate the balance of electrons and holes through functional layers such as electron transport layers, thus slowing down the aging rate of blue light materials. Therefore, in the light-emitting layer group 201, the first light-emitting layer 210 uses red light materials, the second light-emitting layer 220 uses green light materials, and the third light-emitting layer 230 uses blue light materials.

[0057] The peak wavelength of the emitted light from the first emitting layer 210 is located at 600-700 nm, the peak wavelength of the emitted light from the second emitting layer 220 is located at 500-600 nm, and the peak wavelength of the emitted light from the third emitting layer 230 is located at 400-500 nm. It should be noted that the emission peaks of the multiple sub-emitting layers 211 included in the first emitting layer 210 can be located at different wavelengths, as long as their emission peaks are within the range of 500-600 nm.

[0058] The light-emitting device provided in this embodiment configures the first light-emitting layer 210 as a multilayer sub-light-emitting layer 211. In the direction from the anode 300 to the cathode 100, the highest occupied molecular orbital energy levels of the main material of the multilayer sub-light-emitting layer 211 decrease sequentially. This allows holes to be temporarily captured by the sub-light-emitting layer 211 with lower highest occupied molecular orbital energy levels under low voltage, reducing the migration efficiency of holes under low voltage. Consequently, the recombination region of holes and electrons is closer to the first light-emitting layer 210 under low voltage. However, under high voltage, since the electron migration rate is greater than that of the hole, the recombination region of holes and electrons is closer to the first light-emitting layer 210. The migration speed of holes and the recombination region of electrons and holes are close to the first light-emitting layer 210. Therefore, by setting up a multi-layered sub-light-emitting layer 211 with the highest occupied molecular orbital energy level of the host material decreasing sequentially, the recombination region of electrons and holes is close to the first light-emitting layer 210 regardless of whether the voltage is high or low. In this way, the recombination region of electrons and holes is fixed under voltage changes, and the light intensity ratio of the light emitted by the first light-emitting layer 210 and the second light-emitting layer 220 remains unchanged, thereby avoiding the phenomenon of color point drift in the display device under different voltages.

[0059] The light-emitting device provided in the embodiments of this disclosure will now be described with reference to specific examples: Example 1: Reference Figure 4The light-emitting device includes a cathode 100, a light-emitting functional layer 200, and an anode 300 stacked together. From the anode 300 to the cathode 100, the light-emitting functional layer 200 includes a stacked hole injection layer HIL, a first hole transport layer HTL1, a first electron blocking layer prime1, a light-emitting layer group 201, a first electron transport layer ETL1, a charge generation layer 240, a second hole transport layer HTL2, a second electron blocking layer prime2, a third light-emitting layer 230, a second electron transport layer ETL2, and an electron injection layer EIL. The light-emitting layer group 201 includes... The system comprises a first light-emitting layer 210 and a second light-emitting layer 220, which are stacked. The first light-emitting layer 210 is a red light-emitting layer, the second light-emitting layer 220 is a green light-emitting layer, and the third light-emitting layer 230 is a blue light-emitting layer. The first light-emitting layer 210 includes a first sub-light-emitting layer 211a near the anode 300 and a second sub-light-emitting layer 211b located on the side of the first sub-light-emitting layer 211a facing away from the anode 300. The highest occupied molecular orbital energy level of the host material of the first sub-light-emitting layer 211a is higher than that of the host material of the second sub-light-emitting layer 211b. Specifically, the highest occupied molecular orbital energy level of the host material of the first sub-light-emitting layer 211a is -5.0 eV, the highest occupied molecular orbital energy level of the host material of the second sub-light-emitting layer 211b is -5.5 eV, and the highest occupied molecular orbital energy level of the host material of the second light-emitting layer 220 is -5.3 eV.

[0060] The light-emitting device was tested, and the following results were obtained: Figure 5 The emission spectrum shown is as follows: Figure 5 As shown, at voltages of 6V and 8.5V, the ratio of the luminous intensity of red light to green light is approximately 1.4; the color point coordinates of the display device using this light-emitting device were tested, and the results are as follows. Figure 6 The results shown are based on Figure 6 The difference in red light color points with voltage variation is below 0.0005, and the difference in blue light color points with voltage variation is below 0.02. This indicates that the light-emitting device in this example can maintain the ratio of red and green light intensity at a fixed value under different voltages, so that the color points of different colors will not shift with voltage variation, thus improving the phenomenon of color deviation in the display device caused by voltage variation.

[0061] Example 2: Reference Figure 8The light-emitting device includes a cathode 100, a light-emitting functional layer 200, and an anode 300 stacked together. From the anode 300 to the cathode 100, the light-emitting functional layer 200 includes a stacked hole injection layer HIL, a first hole transport layer HTL1, a first electron blocking layer prime1, a third light-emitting layer 230, a first electron transport layer ETL1, a charge generation layer 240, a second hole transport layer HTL2, a second electron blocking layer prime2, a light-emitting layer group 201, a second electron transport layer ETL2, and an electron injection layer EIL. The light-emitting layer group 201 includes... The light-emitting layer includes a first light-emitting layer 210 and a second light-emitting layer 220 stacked together. The first light-emitting layer 210 is a red light-emitting layer, the second light-emitting layer 220 is a green light-emitting layer, and the third light-emitting layer 230 is a blue light-emitting layer. The first light-emitting layer 210 includes a first sub-light-emitting layer 211a near the anode 300 and a second sub-light-emitting layer 211b located on the side of the first sub-light-emitting layer 211a away from the anode 300. The highest occupied molecular orbital energy level of the host material of the first sub-light-emitting layer 211a is higher than the highest occupied molecular orbital energy level of the host material of the second sub-light-emitting layer 211b.

[0062] Example 3: Reference Figure 10 , Figure 10 A schematic diagram of the structure of the light-emitting device provided in this example is shown, as follows: Figure 10 As shown, the light-emitting device includes a cathode 100, a light-emitting functional layer 200, and an anode 300 stacked together. From the anode 300 to the cathode 100, the light-emitting functional layer 200 includes a stacked hole injection layer HIL, a first hole transport layer HTL1, a first electron blocking layer prime1, a light-emitting layer group 201, a first electron transport layer ETL1, a charge generation layer 240, a second hole transport layer HTL2, a second electron blocking layer prime2, a third light-emitting layer 230, a second electron transport layer ETL2, and an electron injection layer EIL. The light-emitting layer group 201 includes a stacked first light-emitting layer 210 and a second light-emitting layer 220. 210 is a red emitting layer, 220 is a green emitting layer, and 230 is a blue emitting layer. In the direction from the anode 300 to the cathode 100, the first emitting layer 210 includes a stacked first sub-emitting layer 211a, a second sub-emitting layer 211b, and a third sub-emitting layer 211c. The highest occupied molecular orbital energy level of the host material of the first sub-emitting layer 211a is higher than that of the host material of the second sub-emitting layer 211b; the highest occupied molecular orbital energy level of the host material of the second sub-emitting layer 211b is higher than that of the host material of the third sub-emitting layer 211c. (Referring to...) Figure 11 , Figure 11 A schematic diagram of the bulk material energy levels of the multiple light-emitting layers in the light-emitting layer group 201 is shown, as follows: Figure 11 As shown, the highest occupied molecular orbital energy level of the host material of the second luminescent layer 220 is located between the highest occupied molecular orbital energy levels of the host material of the first sub-luminescent layer 211a, the second sub-luminescent layer 211b, and the third sub-luminescent layer 211c.

[0063] Based on the same inventive concept, this disclosure also provides a display panel including the light-emitting device described in any of the above embodiments.

[0064] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0065] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0066] The above provides a detailed description of a light-emitting device and display panel provided by this disclosure. Specific examples have been used to illustrate the principles and implementation methods of this disclosure. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this disclosure. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this disclosure. Therefore, the content of this specification should not be construed as a limitation of this disclosure.

[0067] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This disclosure is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.

[0068] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

[0069] The terms "an embodiment," "embodiment," or "one or more embodiments" as used herein mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of this disclosure. Furthermore, please note that the examples of the phrase "in one embodiment" do not necessarily all refer to the same embodiment.

[0070] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of this disclosure may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0071] In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. This disclosure can be implemented by means of hardware comprising a plurality of different elements and by means of a suitably programmed computer. In a unit claim enumerating a plurality of means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words may be interpreted as names.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit them. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this disclosure.

Claims

1. A light-emitting device, characterized in that, It includes a cathode, a light-emitting functional layer, and an anode stacked together; wherein the light-emitting functional layer includes a group of light-emitting layers, a charge-generating layer, and a third light-emitting layer stacked together; The light-emitting layer group includes a first light-emitting layer and a second light-emitting layer stacked together, wherein the first light-emitting layer and the second light-emitting layer emit light of different colors; The first light-emitting layer includes multiple sub-light-emitting layers stacked together. Among the multiple sub-light-emitting layers, the highest occupied molecular orbital energy level of the main material of the sub-light-emitting layer closest to the anode side is the highest.

2. The light-emitting device according to claim 1, characterized in that, In the direction from the first luminescent layer to the second luminescent layer, the highest occupied molecular orbital energy levels of the host materials of the plurality of sub-luminescent layers decrease sequentially.

3. The light-emitting device according to claim 2, characterized in that, In the plurality of sub-light-emitting layers, the difference in the highest occupied molecular orbital energy level of the host material of two adjacent sub-light-emitting layers is less than 0.5 eV.

4. The light-emitting device according to claim 1, characterized in that, The total thickness of the first light-emitting layer is 50-200 angstroms.

5. The light-emitting device according to claim 4, characterized in that, The first light-emitting layer includes a first sub-light-emitting layer close to the anode, and a second sub-light-emitting layer located on the side of the first sub-light-emitting layer opposite to the anode; The thickness ratio of the first sub-light-emitting layer to the second sub-light-emitting layer is 1:4-4:

1.

6. The light-emitting device according to claim 1, characterized in that, The light-emitting layer group is located close to the anode, and in the light-emitting layer group, the second light-emitting layer is located on the side of the first light-emitting layer that is close to the charge-generating layer.

7. The light-emitting device according to claim 1, characterized in that, The light-emitting layer group is close to the cathode, and in the light-emitting layer group, the second light-emitting layer is located on the side of the first light-emitting layer away from the charge-generating layer.

8. The light-emitting device according to claim 1, characterized in that, The highest occupied molecular orbital energy level of the host material of at least one of the sub-light-emitting layers is greater than the highest occupied molecular orbital energy level of the host material of the second light-emitting layer.

9. The light-emitting device according to claim 8, characterized in that, The highest occupied molecular orbital energy level of the host material of the second luminescent layer is located between the highest occupied molecular orbital energy levels of the host materials of the plurality of sub-luminescent layers.

10. The light-emitting device according to any one of claims 1-9, characterized in that, The peak wavelength of the emitted light from the first light-emitting layer is 600-700 nm, the peak wavelength of the emitted light from the second light-emitting layer is 500-600 nm, and the peak wavelength of the emitted light from the third light-emitting layer is 400-500 nm.

11. A display panel, characterized in that, Includes the light-emitting device according to any one of claims 1-10.

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