A white electroluminescent element, a display panel, a light source, and a display device

Abstract

The present invention provides a white electroluminescent element, a display panel, a light source, and a display device, which include an anode, a red light-emitting layer, a green light-emitting layer, a blue light-emitting layer, and a cathode. The red light-emitting layer is located between the anode and the green light-emitting layer, the green light-emitting layer is located between the red light-emitting layer and the blue light-emitting layer, and the blue light-emitting layer is located between the green light-emitting layer and the cathode. The red light-emitting layer includes a red host material, the green light-emitting layer includes a green host material, and the blue light-emitting layer includes a blue host material. The HOMO energy level of the green host material is higher than that of the red host material, and the HOMO energy level of the green host material is higher than that of the blue host material. The LUMO energy level of the green host material is lower than that of the red host material, and the LUMO energy level of the green host material is lower than that of the blue host material. The present invention provides a white electroluminescent element, a display panel, a light source, and a display device to achieve improvement in white light emission efficiency and improvement in device stability.

Description

Technical Field

[0001] The present invention relates to the field of display technologies, and in particular, to a white electroluminescent element, a display panel, a light source, and a display device. Background Art

[0002] As a new generation of display technology, organic electroluminescent materials (OLEDs) have the advantages of being ultrathin, self-luminous, wide viewing angle, fast response, high luminous efficiency, good temperature adaptability, simple production process, low driving voltage, and low energy consumption, and have been widely used in industries such as flat panel displays, flexible displays, solid-state lighting, and vehicle-mounted displays.

[0003] According to the light-emitting mechanism, the materials that can be used in the OLED light-emitting layer mainly include fluorescent materials, phosphorescent materials, triplet-triplet annihilation (TTA) materials, and thermally activated delayed fluorescence (TADF) materials. Among them, TADF materials have a low singlet-triplet energy level difference, and triplet excitons in the light-emitting layer can be converted into singlet excitons via TADF materials under thermal perturbation. In theory, a light-emitting device using the TADF principle can achieve 100% internal quantum efficiency. Summary of the Invention

[0004] The present invention provides a white electroluminescent element, a display panel, a light source, and a display device to improve the white light emission efficiency and the device stability.

[0005] In a first aspect, an embodiment of the present invention provides a white electroluminescent element, including an anode, a red light-emitting layer, a green light-emitting layer, a blue light-emitting layer, and a cathode. The red light-emitting layer is located between the anode and the green light-emitting layer, the green light-emitting layer is located between the red light-emitting layer and the blue light-emitting layer, and the blue light-emitting layer is located between the green light-emitting layer and the cathode;

[0006] The red light-emitting layer includes a red host material, the green light-emitting layer includes a green host material, and the blue light-emitting layer includes a blue host material;

[0007] The HOMO energy level of the green host material is higher than the HOMO energy level of the red host material, and the HOMO energy level of the green host material is higher than the HOMO energy level of the blue host material; the LUMO energy level of the green host material is lower than the LUMO energy level of the red host material, and the LUMO energy level of the green host material is lower than the LUMO energy level of the blue host material.

[0008] In a second aspect, an embodiment of the present invention provides a display panel, including the white electroluminescent element described in the first aspect.

[0009] In a third aspect, an embodiment of the present invention provides a light source, including the white electroluminescent element described in the first aspect.

[0010] In a fourth aspect, an embodiment of the present invention provides a display device, including the display panel described in the second aspect, or a light source as described in the third aspect.

[0011] In an embodiment of the present invention, the HOMO energy level of the green host material is higher than that of the red host material, the HOMO energy level of the green host material is higher than that of the blue host material, the LUMO energy level of the green host material is lower than that of the red host material, and the LUMO energy level of the green host material is lower than that of the blue host material. The energy level of the red host material is relatively shallow and the hole mobility is high. Setting the red light-emitting layer adjacent to the anode is beneficial to the injection of holes. The energy level of the blue host material is relatively deep and the electron mobility is high. Setting the blue light-emitting layer adjacent to the cathode is beneficial to the injection of electrons. Further, holes and electrons are confined in the green light-emitting layer, and holes and electrons recombine to form excitons in the green light-emitting layer. Since the green light-emitting layer is located between the red light-emitting layer and the blue light-emitting layer, the excitons formed in the green light-emitting layer transmit energy to the red light-emitting layer and the blue light-emitting layer on both sides of the green light-emitting layer. The distances for the excitons formed in the green light-emitting layer to transmit energy to the red light-emitting layer and the blue light-emitting layer are both short, improving the white light emission efficiency and the device stability. Description of the Drawings

[0012] Figure 1 It is a schematic cross-sectional structure diagram of a white electroluminescent element provided by an embodiment of the present invention;

[0013] Figure 2 It is a schematic energy level diagram of a white electroluminescent element provided by an embodiment of the present invention;

[0014] Figure 3 It is a schematic energy level diagram of another white electroluminescent element provided by an embodiment of the present invention;

[0015] Figure 4 It is a schematic energy transfer diagram of a white electroluminescent element provided by an embodiment of the present invention;

[0016] Figure 5 It is a schematic energy transfer diagram of another white electroluminescent element provided by an embodiment of the present invention;

[0017] Figure 6 It is a schematic energy level diagram of another white electroluminescent element provided by an embodiment of the present invention;

[0018] Figure 7 It is a schematic energy transfer diagram of another white electroluminescent element provided by an embodiment of the present invention;

[0019] Figure 8Another cross-sectional structure diagram of a white electroluminescent element provided by an embodiment of the present invention;

[0020] Figure 9 Another energy level diagram of a white electroluminescent element provided by an embodiment of the present invention;

[0021] Figure 10 A cross-sectional structure diagram of a display panel provided by an embodiment of the present invention;

[0022] Figure 11 A cross-sectional structure diagram of a light source provided by an embodiment of the present invention;

[0023] Figure 12 A schematic diagram of a display device provided by an embodiment of the present invention. Detailed implementation manners

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the sake of description, only parts related to the present invention are shown in the drawings, rather than all the structures.

[0025] Figure 1 A cross-sectional structure diagram of a white electroluminescent element provided by an embodiment of the present invention, Figure 2 An energy level diagram of a white electroluminescent element provided by an embodiment of the present invention. Refer to Figure 1 and Figure 2 , the white electroluminescent element 10 includes an anode 12, a red light-emitting layer 13, a green light-emitting layer 14, a blue light-emitting layer 15, and a cathode 16. The red light-emitting layer 13 is located between the anode 12 and the green light-emitting layer 14, the green light-emitting layer 14 is located between the red light-emitting layer 13 and the blue light-emitting layer 15, and the blue light-emitting layer 15 is located between the green light-emitting layer 14 and the cathode 16. Among them, the red light-emitting layer 13 is used to generate red light, the green light-emitting layer 14 is used to generate green light, and the blue light-emitting layer 15 is used to generate blue light. The red light, green light, and blue light are combined to form white light.

[0026] The red light-emitting layer 13 includes a red host material 131, the green light-emitting layer 14 includes a green host material 141, and the blue light-emitting layer 15 includes a blue host material 151. The HOMO energy level of the green host material 141 is higher than the HOMO energy level of the red host material 131, and the HOMO energy level of the green host material 141 is higher than the HOMO energy level of the blue host material 151. The LUMO energy level of the green host material 141 is lower than the LUMO energy level of the red host material 131, and the LUMO energy level of the green host material 141 is lower than the LUMO energy level of the blue host material 151.

[0027] Among them, HOMO and LUMO refer to the Highest Occupied Molecular Orbital and the Lowest Unoccupied Molecular Orbital respectively. According to the frontier orbital theory, the two are collectively referred to as the frontier orbitals, and the electrons in the frontier orbitals are called frontier electrons. The energy difference between HOMO and LUMO is called the "band gap", and this energy difference is called the HOMO-LUMO energy level, which can sometimes be used to measure whether a molecule is easily excited: the smaller the band gap, the easier the molecule is to be excited. The HOMO in organic semiconductors and quantum dots is similar to the valence band in inorganic semiconductors, while LUMO is similar to the conduction band.

[0028] In the embodiments of the present invention, the HOMO energy level of the green host material 141 is higher than that of the red host material 131, the HOMO energy level of the green host material 141 is higher than that of the blue host material 151, the LUMO energy level of the green host material 141 is lower than that of the red host material 131, and the LUMO energy level of the green host material 141 is lower than that of the blue host material 151. The energy level of the red host material 131 is relatively shallow and the hole mobility is high. Setting the red light-emitting layer 13 close to the anode 12 is beneficial to the injection of holes. The energy level of the blue host material 151 is relatively deep and the electron mobility is high. Setting the blue light-emitting layer 15 close to the cathode 16 is beneficial to the injection of electrons. Further, holes and electrons are confined in the green light-emitting layer 14, and the holes and electrons recombine to form excitons in the green light-emitting layer 14. Since the green light-emitting layer 14 is located between the red light-emitting layer 13 and the blue light-emitting layer 15, the excitons formed in the green light-emitting layer 14 transmit energy to the red light-emitting layer 13 and the blue light-emitting layer 15 on both sides of the green light-emitting layer 14. The distances for the excitons formed in the green light-emitting layer 14 to transmit energy to the red light-emitting layer 13 and the blue light-emitting layer 15 are both short, which improves the white light emission efficiency and the device stability.

[0029] Figure 3 is the energy level schematic diagram of another white electroluminescent element provided by the embodiments of the present invention. Refer to Figure 3, the red light-emitting layer 13 further includes a red guest material 132. The HOMO energy level of the red host material 131 is lower than that of the red guest material 132, and the LUMO energy level of the red host material 131 is higher than that of the red guest material 132. Both the HOMO energy level and the LUMO energy level of the red guest material 132 are included within the HOMO energy level and the LUMO energy level of the red host material 131. When the energy gap of the red host material 131 is too large, excitons are not easily transferred to the red host material 131 but are easily directly transferred to the red guest material 132, causing the red guest material 132 to emit light.

[0030] Figure 4 FIG. is an energy transfer schematic diagram of a white electroluminescent device provided by an embodiment of the present invention. Since the excitons in the green light-emitting layer 14 are not easily transferred to the red host material 131 but are easily directly transferred to the red guest material 132. In Figure 4 , the energy levels of the red host material 131 are not shown, and only the energy levels of the red guest material 132 are schematically shown. Further, since the red guest material 132 emits phosphorescence instead of fluorescence. In Figure 4 , the singlet energy levels of the red guest material 132 are not shown, and only the triplet energy levels of the red guest material 132 are schematically shown. Referring to Figure 3 and Figure 4 , the triplet energy level of the green host material 141 is greater than the triplet energy level of the red guest material 132. The triplet excitons of the green host material 141 transfer energy to the triplet excitons of the red guest material 132, and the triplet excitons of the green host material 141 return to the ground state. During the process of the triplet excitons of the red guest material 132 returning to the ground state S0, phosphorescence is generated.

[0031] It should be noted that the light generated by the transition of singlet excitons is called fluorescence, and the light generated by the transition of triplet excitons is called phosphorescence. The singlet state is also called the singlet state, and the triplet state is also called the triplet state.

[0032] Exemplarily, the triplet excitons of the green host material 141 can transfer energy to the triplet excitons of the red guest material 132 through Dexter energy transfer. Dexter energy transfer is a way to transfer energy by electron exchange at a short distance, and the electron transfer must comply with the Wigner-Witmer selection rule, that is, the electron spin parameters of both remain fixed before and after the transfer process. This mechanism only acts on relatively neighboring molecules, so this process is relatively slow.

[0033] Optionally, referring to Figure 3 and Figure 4, the green host material 141 includes a thermally activated delayed fluorescence (TADF) material. The energy level difference between the S1 state and the T1 state of the TADF material is relatively small. The T1 state can undergo reverse intersystem crossing back to the S1 state under thermal excitation conditions, and then radiative transition occurs to generate fluorescence. Among them, the S1 state is the first singlet excited state, and the T1 state is the first triplet excited state.

[0034] Exemplarily, the energy level difference between the S1 state and the T1 state of the TADF material is denoted as △Est, and △Est < 0.3 eV.

[0035] Figure 5 FIG. is an energy transfer schematic diagram of another white electroluminescent device provided by an embodiment of the present invention. Refer to Figure 3 and Figure 5 , the blue host material 151 includes a triplet-triplet annihilation (TTA) material. Among them, triplet-triplet annihilation, also known as TTA (triplet-triplet annihilation), utilizes the annihilation effect of excitons in the triplet state to increase the total amount of singlet excitons. Specifically, two triplet excitons annihilate each other to generate a ground state electron and a singlet exciton, and then the generated singlet exciton transitions back to the ground state to emit fluorescence.

[0036] Optionally, refer to Figure 5 , the triplet energy level of the green host material 141 is higher than that of the blue host material 151. The triplet excitons of the green host material 141 transfer energy to the triplet excitons of the blue host material 151. The triplet excitons of the blue host material 151 transfer energy to the singlet excitons of the blue host material 151 through the TTA effect.

[0037] Exemplarily, the triplet excitons of the green host material 141 can transfer energy to the triplet excitons of the blue host material 151 by means of Dexter energy transfer.

[0038] Figure 6 FIG. is an energy level schematic diagram of another white electroluminescent device provided by an embodiment of the present invention. Refer to Figure 6 , Figure 7 FIG. is an energy transfer schematic diagram of another white electroluminescent device provided by an embodiment of the present invention. Refer to Figure 6 and Figure 7 , the blue light-emitting layer 15 further includes a blue guest material 152. The HOMO energy level of the blue host material 151 is lower than the HOMO energy level of the blue guest material 152, and the LUMO energy level of the blue host material 151 is lower than the LUMO energy level of the blue guest material 152. The singlet excitons of the blue host material 151 transfer energy to the singlet excitons of the blue guest material 152, and the singlet excitons of the blue guest material 152 then transition back to the ground state to emit fluorescence.

[0039] Optionally, referring to Figure 7 , the triplet energy level of the blue host material 151 is lower than that of the blue guest material 152. If the triplet energy level of the blue host material 151 is higher than that of the blue guest material 152, the triplet excitons of the blue host material 151 will directly transfer energy to the triplet excitons of the blue guest material 152, resulting in too many triplet excitons and causing triplet exciton quenching. In the embodiments of the present invention, by setting the triplet energy level of the blue host material 151 to be lower than that of the blue guest material 152, the number of triplet excitons is reduced, avoiding the reduction of the luminescence efficiency caused by triplet exciton quenching, enabling the blue light-emitting layer 15 to emit light using singlet excitons, and improving the luminescence efficiency of the white electroluminescent device.

[0040] Optionally, referring to Figure 7 , the blue guest material 152 includes a thermally activated delayed fluorescence (TADF) material. The triplet excitons of the blue guest material 152 undergo reverse intersystem crossing back to the singlet state under thermal excitation conditions, that is, singlet excitons are formed, and then radiative transition occurs to generate fluorescence. In the embodiments of the present invention, the number of triplet excitons is reduced, avoiding the reduction of the luminescence efficiency caused by triplet exciton quenching, enabling the blue light-emitting layer 15 to emit light using singlet excitons, and improving the luminescence efficiency of the white electroluminescent device.

[0041] Optionally, the thermally activated delayed fluorescence material includes boron. The thermally activated delayed fluorescence material containing boron has a small energy level difference between the S1 state and the T1 state, which can bring high brightness, low voltage, high efficiency, and a longer service life.

[0042] Exemplarily, the thermally activated delayed fluorescence material includes a boron heterocyclic compound having the structure shown in Chemical Formula I, where X1 and X2 are each independently selected from a single bond, -(R1)C(R2)2, -NR2, BR3, an O atom, and an S atom; R1, R2, and R3 are each independently selected from any one of aryl, heteroaryl, condensed aryl, and condensed heteroaryl; D1 and D2 are each independently selected from a hydrogen atom, a carbazolyl group and its derivative groups having 12 to 40 carbon atoms, a diphenylamino group and its derivative groups having 12 to 40 carbon atoms, and an acridinyl group and its derivative groups having 13 to 40 carbon atoms; D1 and D2 are respectively connected to the benzene ring of the structure shown in Chemical Formula I, and D1 and D2 are not both hydrogen atoms. Wherein, Chemical Formula I is: [[ID=I6]]

[0043]

[0044] Figure 8 This is a schematic cross-sectional structure diagram of another white electroluminescent device provided by the embodiments of the present invention. Figure 9 This is an energy level schematic diagram of another white electroluminescent device provided by the embodiments of the present invention. Referring toFigure 8 and Figure 9 , the white electroluminescent element 10 further includes a hole transport layer 17, and the hole transport layer 17 is located between the anode 12 and the red light-emitting layer 13. The red host material 131 has the same material as the hole transport layer 17. The red host material 131 has the same LUMO energy level and HOMO energy level as the hole transport layer 17. By providing the hole transport layer 17, the hole injection ability is enhanced.

[0045] Optionally, referring to Figure 8 and Figure 9 , the white electroluminescent element 10 further includes a hole blocking layer 18, and the hole blocking layer 18 is located between the blue light-emitting layer 15 and the cathode 16. The HOMO energy level of the hole blocking layer 18 is less than the HOMO energy level of the blue host material 151. A large energy barrier is generated between the hole blocking layer 18 and the blue light-emitting layer 15, and the transfer of holes will be blocked at the interface between the hole blocking layer 18 and the blue light-emitting layer 15. Thus, the probability of recombination of electrons and holes in the light-emitting layer (the light-emitting layer includes the red light-emitting layer 13, the green light-emitting layer 14, and the blue light-emitting layer 15) can be increased.

[0046] Optionally, referring to Figure 1 , on the one hand, since Dexter energy transfer transfers energy by means of short-distance electron exchange, the range of energy transfer is generally within 10 nm; on the other hand, if the film layer is set too thin, due to the limitations of the film-forming process, effective film formation cannot be achieved, or the film-forming quality is too poor. Therefore, in an embodiment of the present invention, the thickness H1 of the red light-emitting layer 13 is 5 nm - 10 nm, and the thickness H3 of the blue light-emitting layer 15 is 5 nm - 10 nm. That is, the thickness H1 of the red light-emitting layer 13 is greater than or equal to 5 nm and less than or equal to 10 nm, and the thickness H3 of the blue light-emitting layer 15 is greater than or equal to 5 nm and less than or equal to 10 nm.

[0047] Exemplarily, referring to Figure 1 , to match the film layer thicknesses of the red light-emitting layer 13 and the blue light-emitting layer 15, the thickness H2 of the green light-emitting layer 14 can be limited to be less than or equal to 10 nm. Further, considering the film-forming performance, preferably, the thickness H2 of the green light-emitting layer 14 is greater than or equal to 5 nm and less than or equal to 10 nm.

[0048] Optionally, in an embodiment, the green light-emitting layer 14 further includes a green guest material, and the doping ratio of the green guest material in the green light-emitting layer 14 is less than 50%. The present invention does not require the LUMO energy level and HOMO energy level of the green guest material, and the LUMO energy level and HOMO energy level of the green guest material do not affect the process of defining the light-emitting center in the green light-emitting layer 14.

[0049] Exemplarily, the green host material has the same material as the hole transport layer 17.

[0050] Figure 10 The figure is a schematic cross-sectional structure diagram of a display panel provided by an embodiment of the present invention. Refer to Figure 10 , the display panel includes the white electroluminescent element 10 in any of the above embodiments. Since the display panel provided by the embodiment of the present invention includes the white electroluminescent element 10, it has the beneficial effects of the above white electroluminescent element 10, that is, improving the white light emission efficiency and improving the device stability.

[0051] Exemplarily, refer to Figure 10 , the display panel further includes a substrate 11, a pixel driving circuit 21, and a pixel defining layer 22. The white electroluminescent element 10 is located on one side of the substrate 11. The pixel driving circuit 21 is located between the substrate 11 and the white electroluminescent element 10, and the pixel driving circuit 21 is connected to the white electroluminescent element 10 for providing a driving voltage or a driving current to the white electroluminescent element 10. The pixel driving circuit 21 may include a plurality of thin film transistors ( Figure 10 exemplarily shows one thin film transistor in the figure), and the pixel driving circuit 21 may further include at least one capacitor. The pixel defining layer 22 is located on the side of the pixel driving circuit 21 away from the substrate 11. The pixel defining layer 22 is provided with a plurality of pixel defining layer openings, and the red light emitting layer 13, the green light emitting layer 14, and the blue light emitting layer 15 are located in the pixel defining layer openings.

[0052] Figure 11 The figure is a schematic cross-sectional structure diagram of a light source provided by an embodiment of the present invention. Refer to Figure 11 , the light source includes the white electroluminescent element 10 in any of the above embodiments. Since the light source provided by the embodiment of the present invention includes the white electroluminescent element 10, it has the beneficial effects of the above white electroluminescent element 10, that is, improving the white light emission efficiency and improving the device stability.

[0053] In one embodiment, the light source can be used as a backlight for a liquid crystal display panel, that is, used as a backlight source. The backlight used as a backlight source can be a side-entry backlight source or a direct-lit backlight source. In the side-entry backlight source, a plurality of white electroluminescent elements 10 are arranged in a row and located at the side end of the light guide plate of the backlight source, and light enters from the side end of the light guide plate. In the direct-lit backlight source, a plurality of white electroluminescent elements 10 are arranged in a matrix of rows and columns and located at the bottom surface of the light guide plate of the backlight source, and light enters from the bottom surface of the light guide plate.

[0054] Figure 12 The figure is a schematic diagram of a display device provided by an embodiment of the present invention. Refer to Figure 12, the display device includes the display panel in the above embodiments or includes the light source in the above embodiments. The display device may specifically be a mobile phone, a tablet computer, a smart wearable device, etc.

[0055] Note that the above is only the preferred embodiment of the present invention and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, re-adjustments, combinations with each other, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments only. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A white electroluminescent element, characterized in that, It includes an anode, a red light-emitting layer, a green light-emitting layer, a blue light-emitting layer and a cathode. The red light-emitting layer is located between the anode and the green light-emitting layer. The green light-emitting layer is located between the red light-emitting layer and the blue light-emitting layer. The blue light-emitting layer is located between the green light-emitting layer and the cathode; The red light-emitting layer includes a red host material. The green light-emitting layer includes a green host material. The blue light-emitting layer includes a blue host material; The HOMO energy level of the green host material is higher than that of the red host material. The HOMO energy level of the green host material is higher than that of the blue host material. The LUMO energy level of the green host material is lower than that of the red host material. The LUMO energy level of the green host material is lower than that of the blue host material; The red light-emitting layer further includes a red guest material. The HOMO energy level of the red host material is lower than that of the red guest material. The LUMO energy level of the red host material is higher than that of the red guest material; and / or, the blue light-emitting layer further includes a blue guest material. The HOMO energy level of the blue host material is lower than that of the blue guest material. The LUMO energy level of the blue host material is lower than that of the blue guest material.

2. The white electroluminescent element according to claim 1, wherein The triplet energy level of the green host material is greater than that of the red guest material.

3. The white electroluminescent element according to claim 1, wherein The green host material includes a thermally activated delayed fluorescence material.

4. The white electroluminescent element according to claim 1, characterized in that, The blue host material includes a triplet-triplet annihilation material.

5. The white electroluminescent element according to claim 1, wherein The triplet energy level of the green host material is greater than that of the blue host material.

6. The white electroluminescent element according to claim 1, wherein, The triplet energy level of the blue host material is less than that of the blue guest material.

7. The white electroluminescent element according to claim 1, wherein The blue guest material includes a thermally activated delayed fluorescence material.

8. The white electroluminescent element according to claim 7, wherein, The thermally activated delayed fluorescence material includes boron element.

9. The white electroluminescent element according to claim 1, wherein, It further includes a hole transport layer which is located between the anode and the red light-emitting layer; The red host material and the hole transport layer have the same material.

10. The white electroluminescent element according to claim 1, wherein, It further includes a hole blocking layer which is located between the blue light-emitting layer and the cathode; The HOMO energy level of the hole blocking layer is less than that of the blue host material.

11. The white electroluminescent element according to claim 1, wherein, The green light-emitting layer further includes a green guest material. The doping ratio of the green guest material in the green light-emitting layer is less than 50%.

12. The white electroluminescent element according to claim 1, characterized in that, The thickness of the red light-emitting layer is 5nm - 10nm; The thickness of the blue light-emitting layer is 5nm - 10nm.

13. A display panel, characterized in that, It includes the white electroluminescent element according to any one of claims 1 - 12.

14. A light source, characterized in that, It includes the white electroluminescent element according to any one of claims 1 - 12.

15. A display device, characterized in that, It includes the display panel according to claim 13, or the light source according to claim 14.

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