Light emitting diode device, display panel and display device

Abstract

The invention discloses a light-emitting diode device, a display panel and a display device.The light-emitting diode device comprises an anode layer, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode layer which are sequentially stacked, the light-emitting layer comprises a first light-emitting layer and a second light-emitting layer which are stacked, and the first light-emitting layer is located on the side, facing the hole transport layer, of the second light-emitting layer; the first light-emitting layer comprises a first host material, and the second light-emitting layer comprises a second host material; wherein the first triplet excited state energy level of the first host material of the first light-emitting layer is greater than the first triplet excited state energy level of the second host material of the second light-emitting layer. According to the scheme, low power consumption of the light-emitting diode device under a high gray scale is ensured, the problem of non-uniform color under a low gray scale is solved, and the display effect is improved.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to a light emitting diode device, a display panel and a display apparatus. Background Art

[0002] Organic Light Emitting Display (OLED) and planar light emitting diode devices based on light emitting diode (LED) technologies have been widely used in various consumer electronic products such as mobile phones, televisions, laptops, desktop computers, etc. due to their advantages such as high image quality, power saving, thin body and wide application range, becoming the mainstream of light emitting diode devices.

[0003] However, current OLED display products are prone to color unevenness at low grayscales. Summary of the invention

[0004] The main technical problem solved by the present application is to provide a light-emitting diode device, a display panel and a display apparatus, which ensure low power consumption at high gray scales while improving the problem of color unevenness at low gray scales, thereby improving the display effect.

[0005] In order to solve the above technical problems, a technical solution adopted in the present application is: to provide a light-emitting diode device, comprising an anode layer, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode layer stacked in sequence, the light-emitting layer comprising a first light-emitting layer and a second light-emitting layer stacked, the first light-emitting layer being located on the side of the second light-emitting layer facing the hole transport layer, the first light-emitting layer comprising a first main material, and the second light-emitting layer comprising a second main material; wherein a first triplet excited state energy level of the first main material of the first light-emitting layer is greater than a first triplet excited state energy level of the second main material of the second light-emitting layer.

[0006] Preferably, a difference between a first triplet excited state energy level of the first host material and a first triplet excited state energy level of the second host material is greater than 0.2 eV.

[0007] Preferably, the first light-emitting layer further includes a first doping material, and the second light-emitting layer further includes a second doping material, wherein the quantum efficiency of the first doping material is lower than the quantum efficiency of the second doping material.

[0008] Preferably, the first doping material includes at least one of a quencher or an organic fluorescent material; and / or the second doping material includes an organic phosphorescent material.

[0009] Preferably, a ratio of the quantum efficiency of the first doping material to the quantum efficiency of the second doping material is less than or equal to 1 / 4.

[0010] Preferably, the first light-emitting layer also includes a first doping material, and the second light-emitting layer also includes a second doping material, wherein the first doping ratio is less than the second doping ratio, the first doping ratio is the volume ratio of the first doping material to the sum of the first main material and the first doping material, and the second doping ratio is the volume ratio of the second doping material to the sum of the second main material and the second doping material.

[0011] Preferably, the ratio of the first doping ratio to the second doping ratio is less than or equal to 1 / 4.

[0012] Preferably, in a stacking direction, the thickness of the first light-emitting layer is smaller than the thickness of the second light-emitting layer.

[0013] Preferably, the thickness ratio of the first light-emitting layer to the second light-emitting layer is less than or equal to 1 / 3.

[0014] Preferably, the luminous efficiency of the first luminous layer is lower than the luminous efficiency of the second luminous layer, and as the electric field strength of the electric field in which the hole transport layer and the electron transport layer are located increases, the increasing speed of the hole mobility of the hole transport layer is greater than the increasing speed of the electron mobility of the electron transport layer;

[0015] Preferably, the mobility change value is defined as the value when the electric field is 1.6x10 5 The mobility at 10 V / cm is related to the electric field 4 The ratio of the mobility change value of the hole to the mobility change value of the electron is greater than or equal to 10.

[0016] Preferably, the light emitting diode device emits red or green light.

[0017] In order to solve the above technical problems, a technical solution adopted in the present application is: to provide a light-emitting diode device, comprising an anode layer, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode layer stacked in sequence, the light-emitting layer comprising a first light-emitting layer and a second light-emitting layer stacked, the first light-emitting layer being located on the side of the hole transport layer facing the hole transport layer; wherein the light-emitting efficiency of the first light-emitting layer is lower than the light-emitting efficiency of the second light-emitting layer, and as the electric field strength of the hole transport layer and the electron transport layer increases, the increasing rate of the hole mobility of the hole transport layer is greater than the increasing rate of the electron mobility of the electron transport layer.

[0018] Preferably, the mobility change value is defined as the value when the electric field is 1.6x10 5 The mobility at 10 V / cm is related to the electric field 4The ratio of the mobility change value of the hole to the mobility change value of the electron is greater than or equal to 10.

[0019] Preferably, the electric field is 10 4 The mobility of holes at 10 V / cm is lower than that of electrons.

[0020] Preferably, the light emitting diode device emits red or green light.

[0021] In order to solve the above technical problem, another technical solution adopted by the present application is: to provide a display panel, including the light emitting diode device in any embodiment.

[0022] The beneficial effect of the present application is as follows: different from the prior art, the light-emitting layer of a light-emitting diode device provided by the present application is arranged as a double-layer structure, and the energy level of the first light-emitting layer close to the hole transport layer is greater than the energy level of the second light-emitting layer close to the electron transport layer, so that a potential barrier is generated between the first light-emitting layer and the second light-emitting layer, and the energy generated when the excitons recombine can only be transferred from the first light-emitting layer to the second light-emitting layer, but cannot be transferred from the second light-emitting layer to the first light-emitting layer, thereby avoiding the energy generated when the excitons recombine in the second light-emitting layer under high voltage from being transferred to the first light-emitting layer with lower luminous efficiency, ensuring that the excitons always generate energy in the second light-emitting layer, so that the luminous efficiency of the light-emitting diode device is always maintained at a high level at a high grayscale, thereby ensuring that the device has lower power consumption.

[0023] The present application provides a light-emitting diode device, in which the mobility of electrons and holes increases with increasing voltage, and as the voltage increases, the rising rate of the hole mobility of the hole transport layer is greater than the rising rate of the electron mobility of the electron transport layer. Due to the difference in the mobility of electrons and holes, under a low voltage state, the region where electrons and holes recombine is close to the hole transport layer, that is, the exciton recombination region is located in the first light-emitting layer. At this time, the luminous efficiency of the OLED device is low, and as the voltage increases, the rising rate of the hole mobility is faster than that of the electron, so that the exciton recombination region gradually shifts toward the electron transport layer, that is, the exciton recombination region gradually moves from the first light-emitting layer to the second light-emitting layer. Since the luminous efficiency of the second light-emitting layer is higher than that of the first light-emitting layer, the OLED device has a higher luminous efficiency under a high voltage state. On the one hand, the light-emitting diode device provided by the present application has a low luminous efficiency in a low-voltage state. Since the voltage is positively correlated with the display grayscale, the light-emitting diode device has a low luminous efficiency in a low grayscale state, thereby increasing the working current of the device in the low grayscale state, so that the anode of the device can be fully initialized when it is turned on, and all devices on the display panel can be turned on at the same time, avoiding the problem of uneven color. On the other hand, the light-emitting diode device provided by the present application has a high luminous efficiency in a high grayscale state, thereby reducing the working current of the device in the high grayscale state and reducing the power consumption of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of an embodiment of a light emitting diode device of the present application;

[0025] Figure 2 It is a schematic diagram showing that the mobility of carriers of the light emitting diode device of the present application varies with the electric field. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and effect of the present application clearer and more specific, the present application is further described in detail with reference to the accompanying drawings and examples. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0027] Since the luminous efficiency of an OLED device is inversely proportional to its operating current, in order to reduce the power consumption of the OLED device in a high grayscale state, the luminous efficiency of the OLED device is usually higher in a high grayscale state. The inventors have found that the above-mentioned setting usually makes the luminous efficiency of the OLED device higher in a low grayscale state, resulting in a low operating current, which makes the anode initialization of the OLED device insufficient when it is turned on, and there are differences in the turn-on time of the OLEDs at different positions of the display panel, which leads to the problem of uneven display color.

[0028] In view of the above technical problems, the present application provides a light emitting diode device 10, referring to Figure 1 , Figure 1 1 is a schematic diagram of the structure of an embodiment of a light-emitting diode device of the present application. The light-emitting diode device 10 is specifically an OLED device, comprising an anode layer 11, a hole transport layer 12, a light-emitting layer 13, an electron transport layer 14 and a cathode layer 15 stacked in sequence, the light-emitting layer 13 comprising a first light-emitting layer 131 and a second light-emitting layer 132 stacked, the first light-emitting layer 131 being located on the side of the second light-emitting layer 132 facing the hole transport layer 12, that is, the first light-emitting layer 131 is disposed between the hole transport layer 12 and the second light-emitting layer 132, and the second light-emitting layer 132 is disposed between the first light-emitting layer 131 and the electron transport layer 14; wherein the first triplet excited state energy level of the first light-emitting layer 131 is greater than the first triplet excited state energy level of the second light-emitting layer 132.

[0029] Specifically, the light-emitting layer 13 generally includes a main material Host and a dopant material Dopant. Among them, the first light-emitting layer 131 includes a first main material Host1 and a first dopant material Dopant1, and the second light-emitting layer 132 includes a second main material Host2 and a second dopant material Dopant2. Generally, a light-emitting material having a hole transport or electron transport function is used as the main material Host, and a small amount of organic fluorescent or phosphorescent material is doped as the dopant material Dopant. The doping ratio is adjusted according to different material properties to achieve the effect of enhancing the lifespan and efficiency of the main luminescence.

[0030] Optionally, in one embodiment, the first triplet excited state energy level of the first host material Host1 is greater than the first triplet excited state energy level of the second host material Host2, that is, T1(Host1)>T1(Host2). Specifically, the difference between the first triplet excited state energy level of the first host material Host1 and the first triplet excited state energy level of the second host material Host2 is greater than 0.2 eV, that is, T1(Host1)-T1(Host2)>0.2 eV. In the present application, the light-emitting layer 13 is configured as a double-layer structure. Since the T1 energy level of the first main material Host1 is greater than the T1 energy level of the second main material Host2, a potential barrier is generated between the first light-emitting layer 131 and the second light-emitting layer 132. The energy generated when the excitons recombine can only be transferred from the first light-emitting layer 131 to the second light-emitting layer 132, but cannot be transferred from the second light-emitting layer 132 to the first light-emitting layer 131. This avoids the energy generated when the excitons recombine in the second light-emitting layer 132 when the voltage is high from being transferred to the first light-emitting layer 131 with lower luminous efficiency, thereby ensuring that the excitons always generate energy in the second light-emitting layer 132, so that the luminous efficiency of the light-emitting diode device 10 is always maintained at a high level when the voltage is high, that is, when the grayscale is high, thereby ensuring that the device has lower power consumption.

[0031] In an optional embodiment, the quantum efficiency of the first doping material Dopant1 is lower than the quantum efficiency of the second doping material Dopant2. For example, the first doping material Dopant1 may include a material with a low quantum efficiency such as a quencher and an organic fluorescent material, and the second doping material Dopant2 may be a material with a high quantum efficiency such as an organic phosphorescent material, so that the quantum efficiency of the first light-emitting layer 131 is lower than the quantum efficiency of the second light-emitting layer 132. Specifically, the ratio of the quantum efficiency of the first doping material Dopant1 to the quantum efficiency of the second doping material Dopant2 is less than or equal to 1 / 4. For example, the first doping material Dopant1 may be an organic fluorescent material with a quantum efficiency of 25%, and the second doping material Dopant2 may be an organic phosphorescent material with a quantum efficiency of 100%.

[0032] In another optional embodiment, the luminous efficiency of the light-emitting layer 13 can also be changed by adjusting the doping ratio. For example, the materials of the first doping material Dopant1 and the second doping material Dopant2 can be the same, and the doping ratio of the first doping material Dopant1 is set to be lower than the doping ratio of the second doping material Dopant2, wherein the doping ratio is defined as the volume ratio of the doping material Dopant to the sum of the host material Host and the doping material Dopant. Specifically, the doping ratio of the first doping material Dopant1, i.e., the first doping ratio, can be 1 / 4 or less of the doping ratio of the second doping material Dopant2, i.e., the second doping ratio.

[0033] The present application also provides a light-emitting diode device 10, wherein the luminous efficiency of the first light-emitting layer 131 is lower than the luminous efficiency of the second light-emitting layer 132, and as the voltage increases, the increasing rate of the hole mobility of the hole transport layer 12 is greater than the increasing rate of the electron mobility of the electron transport layer 14.

[0034] For more details, see Figure 1 Combined with Figure 2 , Figure 2 Schematic diagram showing the change of carrier mobility of the light emitting diode device of the present application with the electric field. For the convenience of illustration, Figure 2The horizontal axis is the 1 / 2 power of the electric field strength, and the vertical axis is the mobility. Among them, the solid line is the change of the mobility of the first carrier (i.e., holes) with the electric field, and the dotted line is the change of the mobility of the second carrier (i.e., electrons) with the electric field. Driven by the voltage, electrons are injected from the cathode layer 15 into the electron transport layer 14, and migrate to the light-emitting layer 13 through the electron transport layer 14 (as shown by the dotted arrow in the figure), and holes are injected from the anode layer 11 into the hole transport layer 12, and migrate to the light-emitting layer 13 through the hole transport layer 12 (as shown by the solid arrow in the figure), and the holes and electrons meet in the light-emitting layer 13, and the two recombine to form excitons, and the excited state energy is transferred through radiation to generate photons and release energy. In the present application, the light-emitting layer 13 is set as a double-layer structure, wherein the mobility of carriers (including electrons and holes) increases with the increase of the electric field strength of the electric field, and as the voltage of the electric field in which the hole transport layer 12 and the electron transport layer 14 are located increases, the rising rate of the hole mobility of the hole transport layer 12 is greater than the rising rate of the electron mobility of the electron transport layer 14, that is, the slope of the solid line is greater than the slope of the dotted line. Due to the difference in the mobility of electrons and holes, under the low voltage state, the area where electrons and holes recombine is close to the hole transport layer 12, that is, the exciton recombination zone is located in the first light-emitting layer 131. At this time, the luminous efficiency of the OLED device is low, and as the voltage increases, the hole mobility increases faster than the electron mobility, so that the exciton recombination zone gradually shifts to the electron transport layer 14, that is, the exciton recombination zone gradually moves from the first light-emitting layer 131 to the second light-emitting layer 132. Since the luminous efficiency of the second light-emitting layer 132 is higher than the luminous efficiency of the first light-emitting layer 131, the OLED device has a higher luminous efficiency under a high voltage state. On the one hand, the light-emitting diode device 10 provided by the present application has a low luminous efficiency in a low-voltage state. Since the voltage is positively correlated with the display grayscale, the light-emitting diode device 10 has a low luminous efficiency in a low-grayscale state, thereby increasing the working current of the device in the low-grayscale state, so that the anode of the device can be fully initialized when it is turned on, and all devices on the display panel can be turned on at the same time, avoiding the problem of uneven color. On the other hand, the light-emitting diode device 10 provided by the present application has a high luminous efficiency in a high-grayscale state, thereby reducing the working current of the device in the high-grayscale state and reducing the power consumption of the device.

[0035] Further, see Figure 2 The mobility change value K is defined as the value when the electric field is 1.6x10 5 The mobility at the electric field strength of 10 V / cm (i.e., the 1 / 2 power of the electric field strength in the figure is 400) is similar to that at the electric field strength of 10 4V / cm (i.e., the 1 / 2 power of the electric field strength in the figure is 100); the ratio of the mobility change value K1 of the hole to the mobility change value K2 of the electron is greater than or equal to 10, that is, K1 / K2≥10. As can be seen from the figure, when the electric field is low, for example, when the 1 / 2 power of the electric field strength is 100, the mobility of holes is lower than that of electrons, so that the position where holes and electrons recombine is closer to the hole transport layer 12, that is, at this time the exciton recombination zone is located in the first light-emitting layer 131 close to the hole transport layer 12, and the luminous efficiency is low; since the hole mobility change value K1 is 10 times or more of the electron mobility change value K2, as the electric field increases, the hole mobility increases rapidly, and when the electric field is high, for example, when the 1 / 2 power of the electric field strength is 400, the hole mobility is higher than the electron mobility, so that the position where holes and electrons recombine is closer to the electron transport layer 14, that is, at this time the exciton recombination zone is located in the second light-emitting layer 132 close to the electron transport layer 14, and the luminous efficiency is higher.

[0036] Optionally, in the stacking direction Z, the thickness d1 of the first light-emitting layer 131 is less than the thickness d2 of the second light-emitting layer 132. Specifically, the thickness ratio of the first light-emitting layer 131 to the second light-emitting layer 132 is less than or equal to 1 / 3. Since the thickness of the first light-emitting layer 131 is smaller, the distance of the first light-emitting layer 131 in the stacking direction Z is less than the distance of the second light-emitting layer 132 in the stacking direction Z, so that the time for holes to pass through the first light-emitting layer 131 and enter the second light-emitting layer 132 is less than the time for electrons to pass through the second light-emitting layer 132 and enter the first light-emitting layer 131, so that holes and electrons have a greater probability of recombining in the second light-emitting layer 132 to generate excitons, further ensuring that, except for low grayscale conditions, the exciton recombination zone is located in the second light-emitting layer 132 with higher luminescence efficiency, thereby ensuring that the light-emitting diode device 10 has lower power consumption.

[0037] Optionally, the light emitting color of the light emitting diode device 10 is red or green. Since the light emitting efficiency of red light emitting materials and green light emitting materials is usually high at low grayscale, the red light emitting diode device 10 and the green light emitting diode device 10 are more likely to have color unevenness caused by excessive light emitting efficiency at low grayscale, especially the red light emitting diode device 10. Therefore, the structure of the light emitting diode device 10 of the present application can be applied only to the red light emitting diode device 10, or to the red light emitting diode device 10 and the green light emitting diode device 10.

[0038] The present application also provides a display panel, including a substrate, and a light emitting diode device 10 in any of the above embodiments arranged on the substrate.

[0039] The present application also provides a display device, including the above-mentioned display panel, which can be a mobile phone, a tablet computer, a wearable smart device, etc. The display panel and display device provided by the present application ensure low power consumption at high grayscale, improve the problem of color unevenness at low grayscale, and improve the display effect.

[0040] The above are only implementation methods of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A light emitting diode device, characterized in that: The invention comprises an anode layer, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode layer which are stacked in sequence, wherein the light-emitting layer comprises a first light-emitting layer and a second light-emitting layer which are stacked, wherein the first light-emitting layer is located on a side of the second light-emitting layer facing the hole transport layer, wherein the first light-emitting layer comprises a first host material, and the second light-emitting layer comprises a second host material; The first triplet excited state energy level of the first host material of the first light-emitting layer is greater than the first triplet excited state energy level of the second host material of the second light-emitting layer.

2. The light emitting diode device according to claim 1, characterized in that: A difference between a first triplet excited state energy level of the first host material and a first triplet excited state energy level of the second host material is greater than 0.2 eV.

3. The light emitting diode device according to claim 1, characterized in that: The first light-emitting layer further includes a first doping material, and the second light-emitting layer further includes a second doping material, wherein the quantum efficiency of the first doping material is lower than the quantum efficiency of the second doping material.

4. The light emitting diode device according to claim 3, characterized in that: The first doping material includes at least one of a quencher or an organic fluorescent material; and / or, The second doping material includes an organic phosphorescent material; Preferably, a ratio of the quantum efficiency of the first doping material to the quantum efficiency of the second doping material is less than or equal to 1 / 4.

5. The light emitting diode device according to claim 1, characterized in that: The first light-emitting layer further includes a first doping material, and the second light-emitting layer further includes a second doping material, wherein the first doping ratio is less than the second doping ratio, the first doping ratio is the volume ratio of the first doping material to the sum of the first main material and the first doping material, and the second doping ratio is the volume ratio of the second doping material to the sum of the second main material and the second doping material; Preferably, the ratio of the first doping ratio to the second doping ratio is less than or equal to 1 / 4.

6. The light emitting diode device according to claim 1, characterized in that: In the stacking direction, the thickness of the first light-emitting layer is smaller than the thickness of the second light-emitting layer; Preferably, the thickness ratio of the first light-emitting layer to the second light-emitting layer is less than or equal to 1 / 3.

7. The light emitting diode device according to claim 1, characterized in that: The luminous efficiency of the first luminous layer is lower than the luminous efficiency of the second luminous layer, and as the electric field strength of the hole transport layer and the electron transport layer increases, the increasing speed of the hole mobility of the hole transport layer is greater than the increasing speed of the electron mobility of the electron transport layer; Preferably, the mobility change value is defined as the value when the electric field is 1.6x10 5 The mobility at 10 V / cm is related to the electric field 4 The ratio of mobility at V / cm; The ratio of the mobility change value of holes to the mobility change value of electrons is greater than or equal to 10; Preferably, the light emitting diode device emits red or green light.

8. A light emitting diode device, characterized in that: It includes an anode layer, a hole transport layer, a light-emitting layer, an electron transport layer and a cathode layer stacked in sequence, wherein the light-emitting layer includes a first light-emitting layer and a second light-emitting layer stacked in sequence, and the first light-emitting layer is located on a side of the hole transport layer facing the hole transport layer; Among them, the luminous efficiency of the first light-emitting layer is lower than the luminous efficiency of the second light-emitting layer, and with the increase of the electric field strength of the hole transport layer and the electron transport layer, the increasing rate of the hole mobility of the hole transport layer is greater than the increasing rate of the electron mobility of the electron transport layer.

9. The light emitting diode device according to claim 8, characterized in that: The mobility change value is defined as the value of the electric field at 1.6x10 5 The mobility at 10 V / cm is related to the electric field 4 The ratio of mobility at V / cm; The ratio of the mobility change value of holes to the mobility change value of electrons is greater than or equal to 10; Preferably, the electric field is 10 4 The mobility of holes at V / cm is less than that of electrons; Preferably, the light emitting diode device emits red or green light.

10. A display panel, characterized in that: The light emitting diode device comprises the light emitting diode device according to any one of claims 1 to 9.

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