Tandem light-emitting device, display panel, and display apparatus

Abstract

A tandem light-emitting device. The tandem light-emitting device comprises a first light-emitting functional portion and a second light-emitting functional portion. Since the thickness of the second light-emitting functional portion is less than or equal to the thickness of the first light-emitting functional portion, the mitigation effect of the first light-emitting functional portion on a surface plasmon effect is superior to that of the second light-emitting functional portion on the surface plasmon effect, such that improvement in light extraction efficiency of a light-emitting material layer closer to a first electrode is superior to improvement in light extraction efficiency of a light-emitting material layer farther from the first electrode. In this way, the light extraction efficiency of the two light-emitting material layers can be better balanced, such that the light extraction efficiency of different light-emitting material layers tends to be consistent, improving light extraction efficiency of the entire tandem light-emitting device, and thus improving power efficiency of the tandem light-emitting device. The present disclosure further provides a display panel comprising the described tandem light-emitting device, and a display apparatus comprising the display panel.

Description

Multilayer light-emitting devices, display panels and display devices

[0001] Cross-references

[0002] This disclosure claims priority to Chinese Patent Application No. 202510104572.2, filed on January 22, 2025, entitled "Stacked Light Emitting Device, Display Panel and Display Apparatus", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of display technology, and more specifically, to a multilayer light-emitting device, a display panel, and a display apparatus. Background Technology

[0004] A multilayer light-emitting device (LED) is a device that connects multiple light-emitting units in series through a charge-generating layer. Compared to single-layer LEDs, multilayer LEDs offer higher luminous brightness, current efficiency, and lifespan.

[0005] However, in practical applications, multilayer light-emitting devices generally suffer from lower power efficiency compared to single-layer light-emitting devices.

[0006] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0007] The purpose of this disclosure is to overcome the problems of high operating voltage and low power efficiency that are common in multilayer light-emitting devices compared to single-layer light-emitting devices, and to provide a multilayer light-emitting device, a display panel, and a display device.

[0008] According to one aspect of this disclosure, a multilayer light-emitting device is provided, comprising a first electrode, a second electrode, a first light-emitting material layer, a second light-emitting material layer, a first light-emitting functional layer, and a second light-emitting functional layer, wherein the second electrode is disposed opposite to the first electrode; the first light-emitting material layer is disposed between the first electrode and the second electrode, and the first light-emitting material layer includes a first blue light-emitting unit; the second light-emitting material layer is disposed between the first light-emitting material layer and the second electrode, and the second light-emitting material layer includes a second blue light-emitting unit; the first light-emitting functional layer includes a first light-emitting functional part, which is disposed between the first blue light-emitting unit and the first electrode; the second light-emitting functional layer includes a second light-emitting functional part, which is disposed between the first blue light-emitting unit and the second blue light-emitting unit, wherein the thickness of the second light-emitting functional part is less than or equal to the thickness of the first light-emitting functional part.

[0009] In one embodiment of this disclosure, the thickness of the first blue light-emitting unit is greater than or equal to the thickness of the second blue light-emitting unit.

[0010] In one embodiment of this disclosure, the first light-emitting material layer further includes a first red light-emitting unit, the second light-emitting material layer includes a second red light-emitting unit, the first light-emitting functional layer further includes a third light-emitting functional part disposed between the first red light-emitting unit and the first electrode, and the second light-emitting functional layer further includes a fourth light-emitting functional part disposed between the first red light-emitting unit and the second red light-emitting unit, the thickness of the fourth light-emitting functional part being greater than or equal to the thickness of the third light-emitting functional part.

[0011] In one embodiment of this disclosure, the first luminescent material layer further includes a first green luminescent unit, the second luminescent material layer further includes a second green luminescent unit, the first luminescent functional layer further includes a fifth luminescent functional part disposed between the first green luminescent unit and the first electrode, the second luminescent functional layer further includes a sixth luminescent functional part, the fourth luminescent functional part is disposed between the first green luminescent unit and the second green luminescent unit, and the thickness of the sixth luminescent functional part is greater than or equal to the thickness of the fifth luminescent functional part.

[0012] In one embodiment of this disclosure, a first hole transport layer is provided on the side of the first light-emitting functional unit, the third light-emitting functional unit and the fifth light-emitting functional unit near the first electrode, and a second hole transport layer is provided on the side of the second light-emitting functional unit, the fourth light-emitting functional unit and the sixth light-emitting functional unit near the first electrode, and the thickness of the first hole transport layer is greater than or equal to the thickness of the second hole transport layer.

[0013] In one embodiment of this disclosure, the refractive index of the first hole transport layer is less than the refractive index of the second hole transport layer.

[0014] In one embodiment of this disclosure, when the wavelength of the emitted light from the stacked light-emitting device is 455-462nm, the difference between the refractive index of the first hole transport layer and the refractive index of the second hole transport layer is greater than or equal to 0.2.

[0015] In one embodiment of this disclosure, the first light-emitting functional unit includes a first electron blocking element, and the second light-emitting functional unit includes a second electron blocking unit. The first electron blocking unit is disposed between the first hole transport layer and the first blue light-emitting unit, and the second electron blocking unit is disposed between the second hole transport layer and the second blue light-emitting unit. The thickness of the first electron blocking unit is greater than or equal to the thickness of the second electron blocking unit.

[0016] In one embodiment of this disclosure, the third light-emitting functional unit includes a third electron blocking element, and the fourth light-emitting functional unit includes a fourth electron blocking unit. The third electron blocking unit is disposed between the first hole transport layer and the first red light-emitting unit, and the fourth electron blocking unit is disposed between the second hole transport layer and the second red light-emitting unit. The thickness of the third electron blocking unit is less than or equal to the thickness of the fourth electron blocking unit.

[0017] In one embodiment of this disclosure, the fifth light-emitting functional unit includes a fifth electron blocking unit, and the sixth light-emitting functional unit includes a sixth electron blocking unit. The fifth electron blocking unit is disposed between the first hole transport layer and the first green light-emitting unit, and the sixth electron blocking unit is disposed between the second hole transport layer and the second green light-emitting unit. The thickness of the fifth electron blocking unit is less than or equal to the thickness of the sixth electron blocking unit.

[0018] In one embodiment of this disclosure, when the wavelength of the emitted light from the stacked light-emitting device is 455-462 nm, the refractive index of the first electron blocking unit is less than or equal to the refractive index of the second electron blocking unit.

[0019] In one embodiment of this disclosure, the second light-emitting functional layer includes a first hole-blocking layer, a first electron transport layer, and a charge-generating layer. The charge-generating layer is disposed between the first light-emitting material layer and the second hole transport layer. The charge-generating layer includes an N-type doped layer and a P-type doped layer. The P-type doped layer is disposed on the side of the N-type doped layer away from the first light-emitting material layer. The first electron transport layer is disposed on the side of the N-type doped layer close to the first light-emitting material layer. The first hole-blocking layer is disposed on the side of the first electron transport layer close to the first light-emitting material layer. The stacked light-emitting device further includes a third light-emitting functional layer, which includes a second hole-blocking layer. The second hole-blocking layer is disposed on the side of the second light-emitting material layer away from the first electrode. The electron mobility of the first hole-blocking layer is equal to that of the second hole-blocking layer.

[0020] In one embodiment of this disclosure, the second light-emitting functional layer includes a first hole-blocking layer and a charge-generating layer. The charge-generating layer is disposed between the first light-emitting material layer and the second hole transport layer. The charge-generating layer includes an N-type doped layer and a P-type doped layer. The P-type doped layer is disposed on the side of the N-type doped layer away from the first light-emitting material layer. The first hole-blocking layer is disposed on the side of the N-type doped layer close to the first light-emitting material layer. The third light-emitting functional layer includes a second hole-blocking layer, which is disposed on the side of the second light-emitting material layer away from the first electrode. The stacked light-emitting device further includes a third light-emitting functional layer, which includes a second hole-blocking layer, which is disposed on the side of the second light-emitting material layer away from the first electrode. The electron mobility of the first hole-blocking layer is greater than that of the second hole-blocking layer.

[0021] In one embodiment of this disclosure, the first luminescent material layer further includes a first red luminescent unit and a first green luminescent unit, and the second luminescent material layer includes a second red luminescent unit and a second green luminescent unit. The sum of the thicknesses of the first red luminescent unit and the second red luminescent unit is greater than or equal to the sum of the thicknesses of the first green luminescent unit and the second green luminescent unit, and the sum of the thicknesses of the first green luminescent unit and the second green luminescent unit is greater than or equal to the sum of the thicknesses of the first blue luminescent unit and the second blue luminescent unit.

[0022] In one embodiment of this disclosure, the doping material of the N-type doped layer is a low work function metal or a low work function metal salt, and the doping concentration of the N-type doped layer is in the range of 1.2% ± 0.8%. The doping material of the P-type doped layer is an organic electronic material or an inorganic metal oxide material, and the doping concentration of the P-type doped layer is in the range of 10% ± 5%.

[0023] According to another aspect of this disclosure, a display panel is provided, including a multilayer light-emitting device provided in any aspect of this disclosure.

[0024] According to another aspect of this disclosure, a display device is provided, including the display panel provided in another aspect of this disclosure.

[0025] The stacked light-emitting device disclosed herein includes a first light-emitting functional unit and a second light-emitting functional unit. The first light-emitting functional unit is disposed between a first light-emitting unit and a first electrode, and the second light-emitting functional unit is connected between two adjacent first light-emitting units. The first and second light-emitting functional units can reduce the influence of surface plasmon resonance on light extraction efficiency. Since the thickness of the second light-emitting functional unit is less than or equal to the thickness of the first light-emitting functional unit, the reduction effect of the first light-emitting functional unit on the surface plasmon resonance is better than that of the second light-emitting functional unit. This results in a better improvement in the light extraction efficiency of the light-emitting material layer closer to the first electrode than in the light extraction efficiency of the light-emitting material layer farther from the first electrode. This can better balance the light extraction efficiency of the two light-emitting material layers, making the light extraction efficiency of different light-emitting material layers tend to be consistent, improving the overall light extraction efficiency of the stacked light-emitting device, and thus improving the power efficiency of the stacked light-emitting device.

[0026] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0027] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0028] Figure 1 is a cross-sectional schematic diagram of the stacked light-emitting device involved in the embodiments of this disclosure when the second light-emitting functional layer includes the first electron transport layer.

[0029] Figure 2 is a schematic diagram showing the relationship between the driving voltage and brightness of the two sets of blue stacked sub-light-emitting devices involved in the embodiments of this disclosure when optical testing was performed on the two sets of blue stacked sub-light-emitting devices, including the first electron transport layer in the second light-emitting functional layer.

[0030] Figure 3 is a cross-sectional schematic diagram of the stacked light-emitting device involved in the embodiments of this disclosure when the second light-emitting functional layer does not include the first electron transport layer.

[0031] Figure 4 is a schematic diagram showing the relationship between the driving voltage and brightness of the two sets of blue stacked sub-light-emitting devices involved in this embodiment of the present disclosure when optical testing was performed on the two sets of blue stacked sub-light-emitting devices, excluding the first electron transport layer in the second light-emitting functional layer. In the figure: 1-First electrode, 2-Second electrode, 3-First light-emitting material layer, 31-First red light-emitting unit, 32-First green light-emitting unit, 33-First blue light-emitting unit, 4-Second light-emitting material layer, 41-Second red light-emitting unit, 42-Second green light-emitting unit, 43-Second blue light-emitting unit, 5-First light-emitting functional layer, 51-Hole injection layer, 52-First hole transport layer, 53-First electron blocking layer, 531-First electron blocking unit, 532-Third electron blocking unit, 533-Fifth electron blocking unit, 501-First light-emitting functional part, 502-Third light-emitting functional part, 503-Fifth light-emitting functional part, 6-Second light-emitting functional part. Energy layer, 61-first hole blocking layer, 62-first electron transport layer, 63-charge generation layer, 631-N-type doped layer, 632-P-type doped layer, 64-second hole transport layer, 65-second electron blocking layer, 651-second electron blocking unit, 652-fourth electron blocking unit, 653-sixth electron blocking unit, 601-second light-emitting functional unit, 602-fourth light-emitting functional unit, 603-sixth light-emitting functional unit, 7-third light-emitting functional layer, 71-second hole blocking layer, 72-second electron transport layer, 73-electron injection layer, 100-blue multilayer sub-light-emitting device, 200-red multilayer sub-light-emitting device, 300-green multilayer sub-light-emitting device. Detailed Implementation

[0032] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore detailed descriptions of them will be omitted. Furthermore, the drawings are merely illustrative of this disclosure and are not necessarily drawn to scale.

[0033] Although relative terms such as "up" and "down" are used in this specification to describe the relative relationship of one component of an icon to another, these terms are used only for convenience, such as according to the orientation of the examples shown in the accompanying drawings. It is understood that if the device of the icon is flipped upside down, the component described as "up" will become the component described as "down." When a structure is "up" of another structure, it may mean that the structure is integrally formed on the other structure, or that the structure is "directly" mounted on the other structure, or that the structure is "indirectly" mounted on the other structure through another structure.

[0034] The terms “a,” “one,” “the,” “the,” and “at least one” are used to indicate the presence of one or more elements / components / etc.; the terms “including” and “having” are used to indicate an open-ended inclusion and to mean that there may be other elements / components / etc. in addition to the listed elements / components / etc.; the terms “first,” “second,” and “third,” etc., are used only as markers and are not a limitation on the number of objects.

[0035] Compared to LCD panels, OLED (Organic Light Emitting Diode) panels have advantages such as high color saturation, low driving voltage, wide viewing angle, flexibility, fast response speed, and simple manufacturing process. As a result, they have gradually replaced LCD panels as the mainstream in the field of small-sized displays (such as mobile phones, watches, and other electronic products). Their development trend is rapidly concentrating on the medium and large-sized fields. Currently, laptops and automotive display devices using OLED panels have already appeared.

[0036] Organic light-emitting diodes (OLEDs) comprise a hole transport layer, a light-emitting material layer, and an electron transport layer. The hole and electron transport layers are disposed between a first electrode 1 (indium tin oxide, ITO) and a second electrode 2 (Al), while the light-emitting material layer is disposed between the hole transport layer and the electron transport layer. To improve the performance of light-emitting devices, light-emitting layer-doped OLEDs have also been proposed. A light-emitting layer-doped OLED is an organic light-emitting device whose light-emitting characteristics are adjusted by incorporating specific dopants into the light-emitting material layer. These dopants can be fluorescent dyes, phosphorescent dyes, or other types of light-emitting materials that can absorb energy and emit light of a specific color. By precisely controlling the concentration and type of dopants, the color, brightness, and efficiency of the device's emission can be optimized.

[0037] To further improve the luminous performance of light-emitting devices, multilayer light-emitting devices (LEDs) have been developed. A multilayer LED is a light-emitting device that connects multiple light-emitting elements in series via a charge-generating layer 63 and is controlled by only one external power supply. Compared to single-layer LEDs, multilayer LEDs offer higher luminous brightness and current efficiency. Both luminous brightness and current efficiency increase exponentially with the number of light-emitting elements connected in series. At the same current density, the lifespan of a multilayer LED is also significantly increased compared to a single-layer LED.

[0038] The reason why multilayer light-emitting devices have better performance than single-layer light-emitting devices is mainly due to the presence of a charge generation layer 63, which is one of the most important factors affecting the performance of multilayer devices. Currently, in multilayer light-emitting devices, the charge generation layer 63 is generally located between the first light-emitting material layer 3 and the second light-emitting material layer 4. The charge generation layer 63 is used to generate electrons and holes. After separation, electrons and holes are injected and transported into the first light-emitting material layer 3 and the second light-emitting material layer 4, respectively, and recombine with holes injected by the first electrode 1 and electrons injected by the second electrode 2.

[0039] Currently, to achieve higher aperture ratios, top-emitting structures are commonly used in light-emitting devices. Top-emitting devices offer higher aperture ratios and device efficiency. For total internal reflection, the first electrode 1 typically uses a thicker silver electrode. While silver electrodes can improve light emissivity, they also generate plasmon resonance and waveguide effects. These effects cause a significant loss in light efficiency, with surface plasmons contributing approximately 30-35% of the light loss, resulting in an emission rate of only about 20-25%. Therefore, multilayer light-emitting devices generally suffer from lower power efficiency compared to single-layer devices.

[0040] Therefore, in order to improve the light extraction efficiency of the stacked light-emitting device and reduce the optical loss caused by the two effects, the film thickness between the first electrode 1 and the light-emitting material layer and between adjacent light-emitting material layers in the stacked light-emitting device is limited to ensure that the light-emitting area of ​​the stacked light-emitting device is as far away from the first electrode 1 as possible.

[0041] Based on this, the present disclosure provides a stacked light-emitting device. As shown in Figures 1 to 4, the stacked light-emitting device includes a first electrode 1, a second electrode 2, at least two light-emitting material layers, a first light-emitting functional layer 5, and a second light-emitting functional layer 6. The second electrode 2 is disposed opposite to the first electrode 1. At least two light-emitting material layers are disposed between the first electrode 1 and the second electrode 2, and each light-emitting material layer includes a first light-emitting unit. The first light-emitting functional layer 5 includes a first light-emitting functional part 501, which is disposed between the first light-emitting unit and the first electrode 1. The second light-emitting functional layer 6 includes a second light-emitting functional part 601, which is connected between two adjacent first light-emitting units. The thickness of the second light-emitting functional part 601 is less than or equal to the thickness of the first light-emitting functional part 501.

[0042] The stacked light-emitting device includes a first light-emitting functional unit 501 and a second light-emitting functional unit 601. The first light-emitting functional unit 501 is disposed between the first light-emitting unit and the first electrode 1, and the second light-emitting functional unit 601 is connected between two adjacent first light-emitting units. The first light-emitting functional unit 501 and the second light-emitting functional unit 601 can reduce the influence of surface plasmon resonance on light extraction efficiency. Since the thickness of the second light-emitting functional unit 601 is less than or equal to the thickness of the first light-emitting functional unit 501, the reduction effect of the first light-emitting functional unit 501 on the surface plasmon resonance is better than that of the second light-emitting functional unit 601. This makes the improvement in light extraction efficiency of the light-emitting material layer closer to the first electrode 1 better than the improvement in light extraction efficiency of the light-emitting material layer farther away from the first electrode 1. This can better balance the light extraction efficiency of the two light-emitting material layers, make the light extraction efficiency of different light-emitting material layers tend to be consistent, improve the light extraction efficiency of the entire stacked light-emitting device, and thus improve the power efficiency of the stacked light-emitting device.

[0043] The stacked light-emitting devices involved in the embodiments of this disclosure will be described in detail below with reference to specific examples.

[0044] As shown in Figure 1, the stacked light-emitting device includes a first electrode 1, a second electrode 2, a first light-emitting material layer 3, a second light-emitting material layer 4, a first light-emitting functional layer 5, a second light-emitting functional layer 6, and a third light-emitting functional layer 7. The first light-emitting material layer 3 is disposed between the first electrode 1 and the second electrode 2, the second light-emitting material layer 4 is disposed between the first light-emitting material layer 3 and the second electrode 2, the first light-emitting functional layer 5 is disposed between the first electrode 1 and the first light-emitting material layer 3, the second light-emitting functional layer 6 is disposed between the first light-emitting material layer 3 and the second light-emitting material layer 4, and the third light-emitting functional layer 7 is disposed between the second light-emitting material layer 4 and the second electrode 2.

[0045] The first light-emitting functional layer 5 includes a hole injection layer 51, a first hole transport layer 52, and a first electron blocking layer 53. The hole injection layer 51 is disposed between the first electrode 1 and the second electrode 2. The first hole transport layer 52 is disposed on the side of the hole injection layer 51 away from the first electrode 1. The first electron blocking layer 53 is disposed on the side of the first hole transport layer 52 away from the first electrode 1. The first electron blocking layer 53 includes a first electron blocking unit 531, a third electron blocking unit 532, and a fifth electron blocking unit 533. The thickness of the first electron blocking unit 531 is less than the thickness of the fifth electron blocking unit 533, and the thickness of the fifth electron blocking unit 533 is less than the thickness of the third electron blocking unit 532.

[0046] The first luminescent material layer 3 includes a first red luminescent unit 31, a first green luminescent unit 32, and a first blue luminescent unit 33. The first blue luminescent unit 33 is disposed on the side of the first electron blocking unit 531 away from the first electrode 1. The first red luminescent unit 31 is disposed on the side of the third electron blocking unit 532 away from the first electrode 1. The first green luminescent unit 32 is disposed on the side of the fifth electron blocking unit 533 away from the first electrode 1. The side of the first red luminescent unit 31 away from the first electrode 1 is higher than the side of the first green luminescent unit 32 away from the first electrode 1, and the side of the first green luminescent unit 32 away from the first electrode 1 is higher than the side of the first blue luminescent unit 33 away from the first electrode 1.

[0047] The second light-emitting functional layer 6 includes a first hole blocking layer 61, a first electron transport layer 62, a charge generation layer 63, a second hole transport layer 64, and a second electron blocking layer 65. The first hole blocking layer 61 is disposed on the side of the first electron blocking unit 531 away from the first electrode 1. The first electron transport layer 62 is disposed on the side of the first hole blocking layer 61 away from the first electrode 1. The charge generation layer 63 includes an N-type doped layer 631 and a P-type doped layer 632. The N-type doped layer 631 is disposed on the side of the first electron transport layer 62 away from the first electrode 1. The P-type doped layer 632 is disposed on the side of the N-type doped layer 631 away from the first electrode 1. The second hole transport layer 64 is disposed on the side of the P-type doped layer 632 away from the first electrode 1.

[0048] The doping material of the N-type doped layer 631 is a low work function metal or a low work function metal salt, and the doping concentration of the N-type doped layer 631 is in the range of 1.2% ± 0.8%. The doping material of the P-type doped layer 632 is an organic electronic material or an inorganic metal oxide material, and the doping concentration of the P-type doped layer 632 is in the range of 10% ± 5%. When the doping material of the N-type doped layer 631 is a low work function metal, the doping material of the N-type doped layer 631 can be at least one of ytterbium or lithium. When the doping material of the N-type doped layer 631 is a low work function metal salt, the doping material of the N-type doped layer 631 can be at least one of lithium carbonate or cesium carbonate.

[0049] The second electron blocking layer 65 is disposed on the side of the second hole transport layer 64 away from the first electrode 1. The second electron blocking layer 65 includes a second electron blocking unit 651, a fourth electron blocking unit 652 and a sixth electron blocking unit 653. The thickness of the second electron blocking unit 651 is less than the thickness of the sixth electron blocking unit 653, and the thickness of the sixth electron blocking unit 653 is less than the thickness of the fourth electron blocking unit 652.

[0050] The second luminescent material layer 4 includes a second red luminescent unit 41, a second green luminescent unit 42, and a second blue luminescent unit 43. The second blue luminescent unit 43 is disposed on the side of the second electron blocking unit 651 away from the first electrode 1. The second red luminescent unit 41 is disposed on the side of the fourth electron blocking unit 652 away from the first electrode 1. The second green luminescent unit 42 is disposed on the side of the sixth electron blocking unit 653 away from the first electrode 1. The side of the second red luminescent unit 41 away from the first electrode 1 is higher than the side of the second green luminescent unit 42 away from the first electrode 1, and the side of the second green luminescent unit 42 away from the first electrode 1 is higher than the side of the second blue luminescent unit 43 away from the first electrode 1.

[0051] It should be noted that the first luminescent material layer 3 also includes a first red luminescent unit 31 and a first green luminescent unit 32, and the second luminescent material layer 4 includes a second red luminescent unit 41 and a second green luminescent unit 42. The sum of the thicknesses of the first red luminescent unit 31 and the second red luminescent unit 41 is greater than or equal to the sum of the thicknesses of the first green luminescent unit 32 and the second green luminescent unit 42, and the sum of the thicknesses of the first green luminescent unit 32 and the second green luminescent unit 42 is greater than or equal to the sum of the thicknesses of the first blue luminescent unit 33 and the second blue luminescent unit 43.

[0052] The third light-emitting functional layer 7 includes a second hole-blocking layer 71, a second electron transport layer 72, and an electron injection layer 73. The second hole-blocking layer 71 is disposed on the side of the second red light-emitting unit 41 away from the first electrode 1. The second electron transport layer 72 is disposed on the side of the second hole-blocking layer 71 away from the first electrode 1. The electron injection layer 73 is disposed on the side of the second electron transport layer 72 away from the first electrode 1. The second electrode 2 is disposed on the side of the electron injection layer 73 away from the first electrode 1.

[0053] Multilayer light-emitting devices typically include a red multilayer sub-light-emitting device 200, a green multilayer sub-light-emitting device 300, and a blue multilayer sub-light-emitting device 100. From an optical perspective, the blue multilayer sub-light-emitting device 100 is the currently commonly used fluorescent light-emitting system. The blue multilayer sub-light-emitting device 100 has the greatest impact on white light because its operating voltage is higher than that of the red and green multilayer sub-light-emitting devices 200 and 300. From the perspective of white light synthesis, improving the performance of the blue multilayer sub-light-emitting device 100, especially its efficiency, has a significant effect on improving white light efficiency. Therefore, the performance of the blue multilayer sub-light-emitting device 100 needs special attention during the design of multilayer light-emitting devices.

[0054] The first light-emitting functional layer 5 includes a first light-emitting functional part 501, which is disposed between the first light-emitting unit and the first electrode 1, and between the first electrode 1 and the first blue light-emitting unit 33. A second light-emitting functional part 601 is disposed between the first blue light-emitting unit 33 and the second blue light-emitting unit 43. The thickness of the second light-emitting functional part 601 is less than or equal to the thickness of the first light-emitting functional part 501.

[0055] Since the thickness of the second light-emitting functional part 601 is less than or equal to the thickness of the first light-emitting functional part 501, the first light-emitting functional part 501 has a better effect on reducing the surface plasmon effect than the second light-emitting functional part 601. This results in the improvement of the light extraction efficiency of the first blue light-emitting unit 33 closer to the first electrode 1 than the improvement of the light extraction efficiency of the second blue light-emitting unit 43 farther from the first electrode 1. This can better balance the light extraction efficiency of the first blue light-emitting unit 33 and the second blue light-emitting unit 43, making the light extraction efficiency of the first blue light-emitting unit 33 and the second blue light-emitting unit 43 tend to be consistent, thereby improving the light extraction efficiency of the entire blue stacked sub-light-emitting device 100 and thus improving the power efficiency of the stacked light-emitting device.

[0056] Improving the performance of the red multilayer sub-light-emitting device 200 and the green multilayer sub-light-emitting device 300 can also improve white light efficiency. The first light-emitting functional layer 5 also includes a third light-emitting functional part 502, which is disposed between the first red light-emitting unit 31 and the first electrode 1. The second light-emitting functional layer 6 also includes a fourth light-emitting functional part 602, which is disposed between the first red light-emitting unit 31 and the second red light-emitting unit 41. The thickness of the fourth light-emitting functional part 602 is greater than or equal to the thickness of the third light-emitting functional part 502. The first light-emitting functional layer 5 also includes a fifth light-emitting functional part 503, which is disposed between the first green light-emitting unit 32 and the first electrode 1. The second light-emitting functional layer 6 also includes a sixth light-emitting functional part 603, which is disposed between the first green light-emitting unit 32 and the second green light-emitting unit 42. The thickness of the sixth light-emitting functional part 603 is greater than or equal to the thickness of the fifth light-emitting functional part 503.

[0057] For the red multilayer sub-light-emitting device 200, the third light-emitting functional unit 502 has a better effect on reducing the surface plasmonic effect than the fourth light-emitting functional unit 602. This makes the improvement in the light extraction efficiency of the first red light-emitting unit 31 closer to the first electrode 1 better than the improvement in the light extraction efficiency of the second red light-emitting unit 41 farther from the first electrode 1. This can better balance the light extraction efficiency of the first red light-emitting unit 31 and the second red light-emitting unit 41, making the light extraction efficiency of the first red light-emitting unit 31 and the second red light-emitting unit 41 tend to be consistent, thereby improving the light extraction efficiency of the entire red multilayer sub-light-emitting device 200 and thus improving the power efficiency of the multilayer light-emitting device.

[0058] The first light-emitting functional unit 501, the third light-emitting functional unit 502, and the fifth light-emitting functional unit 503 share a hole injection layer 51 and a first hole transport layer 52. A first electron blocking unit 531 is disposed in the first light-emitting functional unit 501, a third electron blocking unit 532 is disposed in the third light-emitting functional unit 502, and a fifth electron blocking unit 533 is disposed in the fifth light-emitting functional unit 503. The second light-emitting functional unit 601, the fourth light-emitting functional unit 602, and the sixth light-emitting functional unit 603 share a first hole blocking layer 61, a first electron transport layer 62, an N-type doped layer 631, a P-type doped layer 632, and a second hole transport layer 64. A second electron blocking unit 651 is disposed in the second light-emitting functional unit 601, a fourth electron blocking unit 652 is disposed in the fourth light-emitting functional unit 602, and a sixth electron blocking unit 653 is disposed in the sixth light-emitting functional unit 603.

[0059] For the blue light-emitting unit, the thickness of the first hole transport layer 52 must be greater than or equal to the thickness of the second hole transport layer 64. This allows the increase in the thickness of the first functional part to be greater than the increase in the thickness of the second light-emitting functional part 601. The first hole transport layer 52 and the second hole transport layer 64 are made of materials with different structures. The refractive index of the first hole transport layer 52 is less than that of the second hole transport layer 64, and the optical path length of the first hole transport layer 52 is greater than that of the second hole transport layer 64. Therefore, the thickness of the first hole transport layer 52 is greater than that of the second hole transport layer 64, ensuring that the first hole transport layer 52 and the second hole transport layer 64 achieve the same refraction angle for the emitted light. In this embodiment, when the wavelength of the emitted light from the stacked light-emitting device is 455-462nm, the emitted light is in the blue light band, and the difference between the refractive indices of the first hole transport layer 52 and the second hole transport layer 64 is greater than or equal to 0.2.

[0060] The first electron blocking unit 531 is disposed between the first hole transport layer 52 and the first blue light-emitting unit 33, and the second electron blocking unit 651 is disposed between the second hole transport layer 64 and the second blue light-emitting unit 43. To further ensure that the thickness of the first light-emitting functional part 501 is greater than the thickness of the second light-emitting functional part 601, the thickness of the first electron blocking unit 531 is set to be greater than or equal to the thickness of the second electron blocking unit 651. This allows the increase in the thickness of the first functional part to be greater than the increase in the thickness of the second light-emitting functional part 601. When the wavelength of the emitted light from the stacked light-emitting device is 455-462nm, the refractive index of the first electron blocking unit 531 is less than or equal to the refractive index of the second electron blocking unit 651, and the optical path length of the first electron blocking unit 531 is greater than the optical path length of the second electron blocking unit 651. Therefore, the thickness of the first electron blocking unit 531 is greater than the thickness of the second electron blocking unit 651, ensuring that the first electron blocking unit 531 and the second electron blocking unit 651 achieve the same refraction angle for the emitted light.

[0061] The third electron blocking unit 532 is disposed between the first hole transport layer 52 and the first red light-emitting unit 31, and the fourth electron blocking unit 652 is disposed between the second hole transport layer 64 and the second red light-emitting unit 41. In order to make the thickness of the fourth light-emitting functional part 602 greater than the thickness of the third light-emitting functional part 502, the thickness of the third electron blocking unit 532 is less than or equal to the thickness of the fourth electron blocking unit 652. The fifth electron blocking unit 533 is disposed between the first hole transport layer 52 and the first green light-emitting unit 32, and the sixth electron blocking unit 653 is disposed between the second hole transport layer 64 and the second green light-emitting unit 42. The thickness of the fifth electron blocking unit 533 is less than or equal to the thickness of the sixth electron blocking unit 653.

[0062] For the blue multilayer sub-light-emitting device 100, in addition to setting the thickness of the first hole transport layer 52 to be greater than the thickness of the second hole transport layer 64, and the thickness of the first electron blocking unit 531 to be greater than the thickness of the second electron blocking unit 651, so that the thickness of the first light-emitting functional unit 501 is greater than or equal to the thickness of the second light-emitting functional unit 601, the thickness of the first blue light-emitting layer can also be set to be greater than or equal to the thickness of the second blue light-emitting layer. This makes the improvement in light extraction efficiency of the first blue light-emitting unit 33 closer to the first electrode 1 more significant than the improvement in light extraction efficiency of the second blue light-emitting unit 43 farther from the first electrode 1. The multilayer light-emitting device with this structure can achieve a 3% increase in current efficiency, light attenuation less than or equal to that of a single-layer blue sub-light-emitting device, and basically does not affect the lifespan of the light-emitting device.

[0063] Furthermore, for the red multilayer sub-light-emitting device 200, the thickness of the first hole transport layer 52 is greater than or equal to the thickness of the second hole transport layer 64, and the thickness of the third electron blocking unit 532 is less than or equal to the thickness of the fourth electron blocking unit 652. This results in an improvement in the light extraction efficiency of the first red light-emitting unit 31 closer to the first electrode 1 compared to an improvement in the light extraction efficiency of the second red light-emitting unit 41 farther from the first electrode 1. For the green multilayer sub-light-emitting device 300, the thickness of the first hole transport layer 52 is greater than or equal to the thickness of the second hole transport layer 64, and the thickness of the fifth electron blocking unit 533 is less than or equal to the thickness of the sixth electron blocking unit 653. This results in an improvement in the light extraction efficiency of the first green light-emitting unit 32 closer to the first electrode 1 compared to an improvement in the light extraction efficiency of the second green light-emitting unit 42 farther from the first electrode 1.

[0064] To ensure that the improvement in light extraction efficiency of the first red light-emitting unit 31, which is closer to the first electrode 1, is greater than the improvement in light extraction efficiency of the second red light-emitting unit 41, which is farther from the first electrode 1, the thickness of the first red light-emitting unit 31 can be set to be less than or equal to the thickness of the second red light-emitting unit 41. Similarly, to ensure that the improvement in light extraction efficiency of the first green light-emitting unit 32, which is closer to the first electrode 1, is greater than the improvement in light extraction efficiency of the second green light-emitting unit 42, which is farther from the first electrode 1, the thickness of the first green light-emitting unit 32 can be set to be less than or equal to the thickness of the second green light-emitting unit 42.

[0065] The material of the first electrode 1 can be indium zinc oxide, and the chemical structural formula of the main material of the hole injection layer 51 is chemical structural formula 1-1:

[0066] The organic dopant of the hole injection layer 51 is 4-[[2,3-bis[cyano-(4-cyano-2,3,5,6-tetrafluorophenyl)methylene]cyclopropylidene]-cyanomethyl]-2,3,5,6-tetrafluorobenzonitrile (NDP9), with an organic dopant content of 3%. The chemical structure of the material of the first hole transport layer 52 is chemical structure formula 1-1. The material of the first electron blocking unit 531 is 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB). The first blue emitting unit 33 includes a blue emitting host material and a blue emitting dopant material. The chemical structure of the blue emitting host material is chemical structure formula 2-1, and the chemical structure of the blue emitting dopant material is chemical structure formula 2-2.

[0067] The doping material ratio of the first blue light-emitting unit 33 can be 1%. The material of the first hole blocking layer 61 is 2,2”,2”-(1,3,5-benzyltriphenyl)tribenzyldiazobenzene (TPBI). The material of the first electron transport layer 62 is 50% 8-hydroxyquinoline-lithium (Liq) doped in copper bath (BCP). The material of the N-type doped layer 631 is 1% ytterbium (Yb) doped in copper bath (BCP). The material of the P-type doped layer 632 is 6% 2,3,5,6-tetrafluoro-7,7,8,-tetracyanidin. The second hole transport layer 64 is made of methyl-p-benzoquinone (F4TCNQ), and its chemical structure is as follows: 1-1; 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB); 43-blue light-emitting unit comprises a blue light-emitting host material and a blue light-emitting dopant material; the chemical structure of the blue light-emitting host material is as follows: 2-1; the chemical structure of the blue light-emitting dopant material is as follows: 2-2; the dopant material content of the second blue light-emitting unit 43 can be 1%; 2,2”,2”-(1,3,5-benzyltriphenyl)tribenzyldiazobenzene (TPBI); 72-8-hydroxyquinoline-lithium (Liq) doped with 50% copper bath (BCP); 73-ytterbium (Yb); and 2-magnesium-silver mixture with a magnesium to silver ratio of 1:9.

[0068] In related technologies, for a blue multilayer light-emitting device, the hole injection layer 51 has a thickness of 10 nm, the first hole transport layer 52 has a thickness of 19 nm, the first electron blocking unit 531 has a thickness of 5 nm, the first blue light-emitting unit 33 has a thickness of 20 nm, the first hole blocking layer 61 has a thickness of 5 nm, the first electron transport layer 62 has a thickness of 100 nm, the N-type doped layer 631 has a thickness of 15 nm, the P-type doped layer 632 has a thickness of 8 nm, the second hole transport layer 64 has a thickness of 21 nm, the second electron blocking unit 651 has a thickness of 5 nm, the second blue light-emitting unit 43 has a thickness of 20 nm, the second hole blocking layer 71 has a thickness of 5 nm, the second electron transport layer 72 has a thickness of 30 nm, the electron injection layer 73 has a thickness of 1 nm, and the second electrode 2 has a thickness of 13 nm.

[0069] In this embodiment, for the blue stacked sub-light-emitting device 100, the hole injection layer 51 has a thickness of 10 nm, the first hole transport layer 52 has a thickness of 27 nm, the first electron blocking unit 531 has a thickness of 10 nm, the first blue light-emitting unit 33 has a thickness of 20 nm, the first hole blocking layer 61 has a thickness of 3 nm, the first electron transport layer 62 has a thickness of 5 nm, the N-type doped layer 631 has a thickness of 12 nm, the P-type doped layer 632 has a thickness of 7 nm, the second hole transport layer 64 has a thickness of 16 nm, the second electron blocking unit 651 has a thickness of 3 nm, the second blue light-emitting unit 43 has a thickness of 20 nm, the second hole blocking layer 71 has a thickness of 5 nm, the second electron transport layer 72 has a thickness of 30 nm, the electron injection layer 73 has a thickness of 1 nm, and the second electrode 2 has a thickness of 13 nm.

[0070] The red tandem light-emitting device 200 differs from the blue tandem light-emitting device 100 in that the thickness of the third electron blocking unit 532 is 8 nm, the thickness of the first red light-emitting unit 31 is 45 nm, the thickness of the fourth electron blocking unit 652 is 26 nm, and the thickness of the second red light-emitting unit 41 is 45 nm. Both the first red light-emitting unit 31 and the second red light-emitting unit 41 include a red light-emitting host material and a red light-emitting dopant material, with the red light-emitting dopant material accounting for 2%. The red light-emitting host material is Bebp2, with the chemical structure formula 3-1, and the red light-emitting dopant material is Ir(MDQ)2(acac), with the chemical structure formula 3-2.

[0071] The green tandem light-emitting device 300 differs from the blue tandem light-emitting device 100 in that the thickness of the third electron blocking unit 532 is 18 nm, the thickness of the first green light-emitting unit 32 is 35 nm, the thickness of the fourth electron blocking unit 652 is 43 nm, and the thickness of the second green light-emitting unit 42 is 35 nm. Both the first green light-emitting unit 32 and the second green light-emitting unit 42 include a green light-emitting host material and a green light-emitting dopant material, with the green light-emitting dopant material accounting for 6%. The green light-emitting host material is TPBi, and its chemical structure formula is 4-1. The green light-emitting dopant material is Ir(ppy)3, and its chemical structure formula is 4-2.

[0072] For the blue stacked sub-light-emitting device 100 in Figure 1, the following verification was performed: the first hole transport layer 52 and the second hole transport material layer were made of the same material as a control group; the first hole transport layer 52 and the second hole transport material layer were made of different materials, and at 455-462 nm, the difference between the refractive index S1 of the first hole transport layer 52 and the refractive index S2 of the second hole transport layer 64, S1-S2 = 0.1, was measured at 10 mA / cm². 2 Optical tests were conducted on two sets of blue tandem sub-light-emitting devices 100 under the following conditions. The test data of the blue tandem sub-light-emitting devices 100 are as follows: when S1-S2 = 0.1, the current efficiency is 92.2 Cd / A; when S1-S2 = 0, the current efficiency is 89.5 Cd / A. It can be seen that when the refractive index S1 of the first hole transport layer 52 is greater than the refractive index S2 of the second hole transport layer 64, the current efficiency of the blue tandem sub-light-emitting device 100 can be significantly improved. As shown in Figure 2, under the same driving voltage, when S1-S2 is 0.1, the relationship curve between the driving voltage and brightness of the blue tandem sub-light-emitting device 100 is L1; when S1-S2 is 0, the relationship curve between the driving voltage and brightness of the blue tandem sub-light-emitting device 100 is L2. Obviously, at the same driving voltage, the brightness corresponding to L1 is higher than that corresponding to L2.

[0073] As shown in Figure 3, the difference from Figure 1 is that a first hole blocking layer 61, a charge generating layer 63, a second hole transport layer 64, and a second electron blocking unit 651 are provided between the first blue light-emitting unit 33 and the second blue light-emitting unit 43. The thickness of the first hole transport layer 52 is greater than or equal to the thickness of the second hole transport layer 64, and the thickness of the first electron blocking unit 531 is greater than or equal to the thickness of the second electron blocking unit 651.

[0074] In addition, for the red stacked sub-light-emitting device 200, a first hole blocking layer 61, a charge generating layer 63, a second hole transport layer 64 and a fourth electron blocking unit 652 are provided between the first red light-emitting unit 31 and the second red light-emitting unit 41. The thickness of the first hole transport layer 52 is greater than or equal to the thickness of the second hole transport layer 64, and the thickness of the third electron blocking unit 532 is less than or equal to the thickness of the fourth electron blocking unit 652.

[0075] For the green stacked sub-light-emitting device 300, a first hole blocking layer 61, a charge generating layer 63, a second hole transport layer 64 and a sixth electron blocking unit 653 are provided between the first green light-emitting unit 32 and the second green light-emitting unit 42. The thickness of the first hole transport layer 52 is greater than or equal to the thickness of the second hole transport layer 64, and the thickness of the fifth electron blocking unit 533 is less than or equal to the thickness of the sixth electron blocking unit 653.

[0076] Because the first electron transport layer 62 has been removed, in order to ensure the electron transport rate, the electron mobility of the first hole blocking layer 61 needs to be increased, that is, the electron mobility of the first hole blocking layer 61 is set to be greater than the electron mobility of the second hole blocking layer 71.

[0077] This stacked light-emitting device structure can achieve a 2% improvement in current efficiency, and the light attenuation is less than or equal to that of a single-layer blue sub-light-emitting device, which basically does not affect the lifespan of the light-emitting device.

[0078] In related technologies, for a blue multilayer light-emitting device, the hole injection layer 51 has a thickness of 10 nm, the first hole transport layer 52 has a thickness of 24 nm, the first electron blocking unit 531 has a thickness of 5 nm, the first blue light-emitting unit 33 has a thickness of 20 nm, the first hole blocking layer 61 has a thickness of 5 nm, the N-type doped layer 631 has a thickness of 15 nm, the P-type doped layer 632 has a thickness of 8 nm, the second hole transport layer 64 has a thickness of 26 nm, the second electron blocking unit 651 has a thickness of 5 nm, the second blue light-emitting unit 43 has a thickness of 20 nm, the second hole blocking layer 71 has a thickness of 5 nm, the second electron transport layer 72 has a thickness of 30 nm, the electron injection layer 73 has a thickness of 1 nm, and the second electrode 2 has a thickness of 13 nm.

[0079] In this embodiment, for the blue stacked sub-light-emitting device 100, the hole injection layer 51 has a thickness of 10 nm, the first hole transport layer 52 has a thickness of 32 nm, the first electron blocking unit 531 has a thickness of 10 nm, the first blue light-emitting unit 33 has a thickness of 20 nm, the first hole blocking layer 61 has a thickness of 3 nm, the N-type doped layer 631 has a thickness of 12 nm, the P-type doped layer 632 has a thickness of 7 nm, the second hole transport layer 64 has a thickness of 21 nm, the second electron blocking unit 651 has a thickness of 3 nm, the second blue light-emitting unit 43 has a thickness of 20 nm, the second hole blocking layer 71 has a thickness of 5 nm, the second electron transport layer 72 has a thickness of 30 nm, the electron injection layer 73 has a thickness of 1 nm, and the second electrode 2 has a thickness of 13 nm.

[0080] For the blue stacked sub-light-emitting device 100 in Figure 3, the following verification was performed: the first hole transport layer 52 and the second hole transport material layer were made of the same material as a control group; the first hole transport layer 52 and the second hole transport material layer were made of different materials, and at 455-462 nm, the difference between the refractive index S1 of the first hole transport layer 52 and the refractive index S2 of the second hole transport layer 64, S1-S2 = 0.1, was measured at 10 mA / cm². 2 Optical tests were conducted on two sets of blue tandem sub-emitting diodes 100 under the following conditions. The test data of the blue tandem sub-emitting diodes 100 are as follows: when S1-S2 = 0.1, the current efficiency is 86.9 Cd / A; when S1-S2 = 0, the current efficiency is 85.1 Cd / A. It can be seen that when the refractive index S1 of the first hole transport layer 52 is greater than the refractive index S2 of the second hole transport layer 64, the current efficiency of the blue tandem sub-emitting diodes 100 can be significantly improved. As shown in Figure 4, under the same driving voltage, when S1-S2 = 0.1, the relationship curve between the driving voltage and brightness of the blue tandem sub-emitting diodes 100 is L4; when S1-S2 is 0, the relationship curve between the driving voltage and brightness of the blue tandem sub-emitting diodes 100 is L3. Obviously, at the same driving voltage, the brightness corresponding to L4 is higher than that corresponding to L3.

[0081] When the electron mobility of the first hole blocking layer 61 is greater than that of the second hole blocking layer 71, the material of the first hole blocking layer 61 is 4,7-diphenyl-1,10-o-phenanthroline (Bphen).

[0082] Two sets of blue multilayer light-emitting devices were set up, and optical tests were performed on the two sets of blue multilayer light-emitting devices 100 under the condition of 10mA / cm2. In the first set of blue multilayer light-emitting devices, the material of the first hole blocking layer 61 is 4,7-diphenyl-1,10-o-phenanthroline (Bphen), and the material of the second hole blocking layer 71 is 2,2”,2”-(1,3,5-benzylbenzene)tribenzyldiazobenzene (TPBI); in the second set of blue multilayer light-emitting devices, the material of the first hole blocking layer 61 is 2,2”,2”-(1,3,5-benzylbenzene)tribenzyldiazobenzene (TPBI), and the material of the second hole blocking layer 71 is 2,2”,2”-(1,3,5-benzylbenzene)tribenzyldiazobenzene (TPBI).

[0083] The specific test data are as follows: When the material of the first hole-blocking layer 61 is 2,2”,2”-(1,3,5-benzylbenzene)tribenzyldiazobenzene (TPBI), the voltage is 9.32V and the current efficiency is 86.9Cd / A. When the material of the first hole-blocking layer 61 is 4,7-diphenyl-1,10-o-phenanthroline (Bphen), the voltage is 9.21V and the current efficiency is 87.8Cd / A. The first group of blue multilayer light-emitting devices can achieve a 1% reduction in operating voltage and a 1% increase in current efficiency.

[0084] This disclosure also provides a display module, which may include the flexible circuit board mentioned above in this disclosure. The specific structure and advantages of this display module can be found in the flexible circuit board, whose specific structure and advantages have been described in detail above and will not be repeated here.

[0085] This disclosure also provides a display panel that may include the multilayer light-emitting device mentioned above. The structure and advantages of the display panel can be referenced to the multilayer light-emitting device, the specific structure and advantages of which have been described in detail above and will not be repeated here.

[0086] This disclosure also provides a display device, which may include the display panel mentioned above in this disclosure. The structure and beneficial effects of the display device can be referred to the display panel, and the specific structure and beneficial effects of the display panel can be referred to the multilayer light-emitting device; therefore, they will not be described in detail here.

[0087] It should be noted that, in addition to the display panel, the display device also includes other necessary components and parts, such as the casing, circuit board, power cord, etc. Those skilled in the art can make corresponding additions according to the specific usage requirements of the display device, which will not be elaborated here.

[0088] Display devices can be traditional electronic devices, such as mobile phones, computers, televisions, and video recorders, or emerging wearable devices, such as virtual reality devices and augmented reality devices, which will not be listed here.

[0089] It should be noted that the above embodiments are interconnected and can be combined to form other solutions. The solutions disclosed herein are not limited to those described in the above embodiments. Those skilled in the art will readily conceive of other embodiments of this disclosure upon considering the specification and practicing the invention disclosed herein. This application 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 embodiments are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the appended claims.

Claims

1. A stacked light-emitting device, wherein, include: First electrode; The second electrode is disposed opposite to the first electrode; A first light-emitting material layer is disposed between the first electrode and the second electrode, and the first light-emitting material layer includes a first blue light-emitting unit; A second light-emitting material layer is disposed between the first light-emitting material layer and the second electrode, and the second light-emitting material layer includes a second blue light unit. The first light-emitting functional layer includes a first light-emitting functional part, which is disposed between the first blue light-emitting unit and the first electrode. The second light-emitting functional layer includes a second light-emitting functional part, which is disposed between the first blue light-emitting unit and the second blue light-emitting unit. The thickness of the second light-emitting functional part is less than or equal to the thickness of the first light-emitting functional part.

2. The stacked light-emitting device according to claim 1, wherein The thickness of the first blue light-emitting unit is greater than or equal to the thickness of the second blue light-emitting unit.

3. The stacked light-emitting device according to claim 2, wherein The first luminescent material layer further includes a first red luminescent unit, the second luminescent material layer includes a second red luminescent unit, the first luminescent functional layer further includes a third luminescent functional part, the third luminescent functional part is disposed between the first red luminescent unit and the first electrode, the second luminescent functional layer further includes a fourth luminescent functional part, the fourth luminescent functional part is disposed between the first red luminescent unit and the second red luminescent unit, and the thickness of the fourth luminescent functional part is greater than or equal to the thickness of the third luminescent functional part.

4. The stacked light-emitting device according to claim 3, wherein, The first luminescent material layer further includes a first green luminescent unit, the second luminescent material layer further includes a second green luminescent unit, the first luminescent functional layer further includes a fifth luminescent functional part, the fifth luminescent functional part is disposed between the first green luminescent unit and the first electrode, the second luminescent functional layer further includes a sixth luminescent functional part, the fourth luminescent functional part is disposed between the first green luminescent unit and the second green luminescent unit, and the thickness of the sixth luminescent functional part is greater than or equal to the thickness of the fifth luminescent functional part.

5. The stacked light-emitting device of claim 4, wherein, The first, third, and fifth light-emitting functional units have a first hole transport layer on the side near the first electrode, and the second, fourth, and sixth light-emitting functional units have a second hole transport layer on the side near the first electrode. The thickness of the first hole transport layer is greater than or equal to the thickness of the second hole transport layer.

6. The stacked light-emitting device according to claim 5, wherein The refractive index of the first hole transport layer is less than that of the second hole transport layer.

7. The stacked light-emitting device according to claim 6, wherein When the wavelength of the emitted light from the stacked light-emitting device is 455-462nm, the difference between the refractive index of the first hole transport layer and the refractive index of the second hole transport layer is greater than or equal to 0.

2.

8. The stacked light-emitting device according to claim 5, wherein The first light-emitting functional unit includes a first electron blocking unit, and the second light-emitting functional unit includes a second electron blocking unit. The first electron blocking unit is disposed between the first hole transport layer and the first blue light-emitting unit, and the second electron blocking unit is disposed between the second hole transport layer and the second blue light-emitting unit. The thickness of the first electron blocking unit is greater than or equal to the thickness of the second electron blocking unit.

9. The stacked light-emitting device of claim 8, wherein, The third light-emitting functional unit includes a third electron blocking element, and the fourth light-emitting functional unit includes a fourth electron blocking unit. The third electron blocking unit is disposed between the first hole transport layer and the first red light-emitting unit, and the fourth electron blocking unit is disposed between the second hole transport layer and the second red light-emitting unit. The thickness of the third electron blocking unit is less than or equal to the thickness of the fourth electron blocking unit.

10. The stacked light-emitting device of claim 9, wherein, The fifth light-emitting functional unit includes a fifth electron blocking unit, and the sixth light-emitting functional unit includes a sixth electron blocking unit. The fifth electron blocking unit is disposed between the first hole transport layer and the first green light-emitting unit, and the sixth electron blocking unit is disposed between the second hole transport layer and the second green light-emitting unit. The thickness of the fifth electron blocking unit is less than or equal to the thickness of the sixth electron blocking unit.

11. The stacked light-emitting device of claim 8, wherein, When the wavelength of the emitted light from the stacked light-emitting device is 455-462nm, the refractive index of the first electron blocking unit is less than or equal to the refractive index of the second electron blocking unit.

12. The stacked light-emitting device of claim 10, wherein, The second light-emitting functional layer includes a first hole-blocking layer, a first electron transport layer, and a charge-generating layer. The charge-generating layer is disposed between the first light-emitting material layer and the second hole transport layer. The charge-generating layer includes an N-type doped layer and a P-type doped layer. The P-type doped layer is disposed on the side of the N-type doped layer away from the first light-emitting material layer. The first electron transport layer is disposed on the side of the N-type doped layer close to the first light-emitting material layer. The first hole-blocking layer is disposed on the side of the first electron transport layer close to the first light-emitting material layer. The stacked light-emitting device further includes a third light-emitting functional layer. The third light-emitting functional layer includes a second hole-blocking layer. The second hole-blocking layer is disposed on the side of the second light-emitting material layer away from the first electrode. The electron mobility of the first hole-blocking layer is equal to the electron mobility of the second hole-blocking layer.

13. The stacked light-emitting device of claim 10, wherein, The second light-emitting functional layer includes a first hole-blocking layer and a charge-generating layer. The charge-generating layer is disposed between the first light-emitting material layer and the second hole transport layer. The charge-generating layer includes an N-type doped layer and a P-type doped layer. The P-type doped layer is disposed on the side of the N-type doped layer away from the first light-emitting material layer. The first hole-blocking layer is disposed on the side of the N-type doped layer close to the first light-emitting material layer. The third light-emitting functional layer includes a second hole-blocking layer, which is disposed on the side of the second light-emitting material layer away from the first electrode. The stacked light-emitting device further includes a third light-emitting functional layer, which includes a second hole-blocking layer, disposed on the side of the second light-emitting material layer away from the first electrode. The electron mobility of the first hole-blocking layer is greater than that of the second hole-blocking layer.

14. The stacked light-emitting device according to claim 4, wherein The first luminescent material layer further includes a first red luminescent unit and a first green luminescent unit, and the second luminescent material layer includes a second red luminescent unit and a second green luminescent unit. The sum of the thicknesses of the first red luminescent unit and the second red luminescent unit is greater than or equal to the sum of the thicknesses of the first green luminescent unit and the second green luminescent unit, and the sum of the thicknesses of the first green luminescent unit and the second green luminescent unit is greater than or equal to the sum of the thicknesses of the first blue luminescent unit and the second blue luminescent unit.

15. The stacked light-emitting device according to claim 12 or 13, wherein The doping material of the N-type doped layer is a low work function metal or a low work function metal salt, and the doping concentration of the N-type doped layer is in the range of 1.2% ± 0.8%. The doping material of the P-type doped layer is an organic electronic material or an inorganic metal oxide material, and the doping concentration of the P-type doped layer is in the range of 10% ± 5%.

16. A display panel, wherein, Includes the stacked light-emitting device according to any one of claims 1 to 15.

17. A display device, wherein, Includes the display panel as described in claim 16.

Images