Light-emitting device and display panel

Abstract

The present disclosure provides a light-emitting device and a display panel. The light-emitting device includes a first electrode, a second electrode, and a light-emitting functional layer located between the first and second electrodes. The light-emitting functional layer includes a light-emitting layer and a first functional layer, the first functional layer being located between the light-emitting layer and the second electrode. The first functional layer includes a photoisomerization material that absorbs light and binds to metal ions. By providing the first functional layer including the photoisomerization material in the light-emitting device, the light-emitting device can be protected from aging due to light exposure while reducing the risk of luminescence quenching due to metal ion intrusion, thereby extending the service life of the light-emitting device.

Description

Technical Field

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

[0002] Organic Light-Emitting Diode (OLED) is an organic thin-film electroluminescent device. It has attracted great attention and is widely used in electronic display products due to its advantages such as simple preparation process, low cost, low power consumption, high brightness, wide viewing angle, high contrast and flexible display.

[0003] However, current OLEDs are limited by their inherent structural design. When used in electronic display products, they can be exposed to harmful light, which can cause internal structural degradation and shorten their lifespan. Furthermore, if metal ions infiltrate the OLED, this can cause luminescence quenching, further reducing the lifespan. Summary of the Invention

[0004] The present disclosure provides a light-emitting device and a display panel. In the light-emitting device, a material that can absorb harmful light and can combine with metal ions is arranged between the light-emitting layer and the second electrode to block the metal ions invading the light-emitting layer, thereby delaying the aging of the light-emitting device and reducing the risk of luminescence quenching.

[0005] According to a first aspect of the present disclosure, a light-emitting device is provided. The light-emitting device includes a first electrode, a second electrode, and a light-emitting functional layer positioned between the first and second electrodes. The light-emitting functional layer includes a light-emitting layer and a first functional layer, wherein the first functional layer is positioned between the light-emitting layer and a cathode. The first functional layer includes a photoisomerization material that absorbs light and binds to metal ions.

[0006] In the above scheme, the first functional layer absorbs light and can combine with metal ions from the second electrode, which can alleviate the aging of the light-emitting device due to light while reducing the risk of luminescence quenching due to the invasion of metal ions, thereby extending the service life of the light-emitting device.

[0007] In a specific embodiment of the first aspect of the present disclosure, the photoisomerization material is used to absorb harmful light and change from a ground state structure to an isomeric structure when exposed to harmful light, and the isomeric structure is combined with metal ions; when there is no harmful light exposure, the isomeric structure is used to change from a ground state structure to a ground state structure, and the ground state structure is combined with or separated from the metal ions.

[0008] In this scheme, the heterostructure combines with metal ions to reduce the risk of luminescence quenching caused by metal ion intrusion. The heterostructure and ground state structure can transform into each other under certain conditions. For example, under specific conditions, such as when there is no external harmful light exposure, the heterostructure will transform into the ground state structure, allowing it to be repeatedly used to absorb harmful light, further extending the life of the light-emitting device.

[0009] In a specific embodiment of the first aspect of the present disclosure, the photo-isomerizable material undergoes cis-trans isomerization upon absorbing harmful light.

[0010] In the above scheme, the photoisomerizable material undergoes cis-trans isomerization when irradiated with harmful light, thereby absorbing the harmful light.

[0011] In a specific embodiment of the first aspect of the present disclosure, the wavelength of the harmful light is different from the wavelength of the light emitted by the light-emitting layer.

[0012] In a specific embodiment of the first aspect of the present disclosure, the harmful light includes at least one of ultraviolet light (UV) and infrared light (IR).

[0013] Infrared light and ultraviolet light are common lights that cause aging of light-emitting devices. In the above solution, the first functional layer including the photoisomerization material can absorb these two types of light, thereby further slowing down the aging of the light-emitting device.

[0014] In a specific embodiment of the first aspect of the present disclosure, the photoisomerization material includes a first group for isomerization and / or a second group for binding to metal ions, the first group includes at least one of azobenzene, C=C, cinnamic acid and benzospiropyran, and the second group includes at least one of a carbonyl group, an amino group, a hydroxyl group, a benzospiropyran group and a phosphono group.

[0015] In the above scheme, the first group of the above-mentioned portion of the photo-isomerizable material can undergo cis-trans isomerization when exposed to harmful light (e.g., the irradiation of the above-mentioned harmful light), that is, it can become an isomer structure. Moreover, after the harmful light is removed, the first group of the isomer structure that is not bound to the metal ion will return to the original state, thereby achieving reuse.

[0016] In a specific embodiment of the first aspect of the present disclosure, the photoisomerization material includes at least one of a quaternary ammonium salt of an o-hydroxyacetophenone derivative, a quaternary ammonium salt of an 8-hydroxyquinoline α,β-unsaturated ketone derivative, and a spiropyran derivative.

[0017] In the above scheme, after exposure to harmful light, some of the photoisomerizable materials, such as quaternary ammonium salts of o-hydroxyacetophenone derivatives, quaternary ammonium salts of 8-hydroxyquinoline α,β-unsaturated ketone derivatives, and spiropyran derivatives, undergo cis-trans isomerization, i.e., conversion to isomerized structures. On this basis, some of the isomerized structures can bind to metal ions. When there is no harmful light exposure, some of the isomerized structures not bound to metal ions, under specific conditions, convert to ground state structures, and some of the ground state structures can bind to metal ions. In this way, when the light-emitting device is exposed to harmful light, the first functional layer can absorb the harmful light to slow down the aging of the light-emitting device, and bind metal ions to reduce the risk of luminescence quenching in the light-emitting device.

[0018] In a specific embodiment of the first aspect of the present disclosure, the first electrode is a reflective electrode; and the second electrode is a transmissive electrode.

[0019] In the above solution, the side of the light emitting device facing the second electrode is its light emitting side, and accordingly, this side is also the side of the light emitting device illuminated by external ambient light.

[0020] In a specific embodiment of the first aspect of the present disclosure, the first functional layer includes a substrate layer doped with a photo-isomerization material;

[0021] The first electrode is an anode, the second electrode is a cathode, and the substrate layer includes at least one of an electron injection layer, an electron transport layer, and a hole blocking layer; or, the first electrode is a cathode, the second electrode is an anode, and the substrate layer includes at least one of a hole injection layer, a hole transport layer, and an electron blocking layer.

[0022] The above solution is conducive to the lightweight and thin design of the light emitting device. In addition, the above design does not require changing the module design of the entire light emitting device (such as the thickness design of each film layer), which is conducive to reducing the design cost of the light emitting device.

[0023] In a specific embodiment of the first aspect of the present disclosure, the mass proportion of the photo-isomerization material in the first functional layer is 0.01% to 10%.

[0024] In the above solution, setting the mass proportion of the photo-isomerization material in the first functional layer to 0.01% to 10% can improve the lifespan while avoiding adverse effects on the current efficiency of the device.

[0025] A second aspect of the present disclosure provides a display panel, which includes a display area, in which a plurality of light-emitting devices according to the first aspect are arranged.

[0026] The photoisomerization material disclosed herein can absorb harmful light and form a complex with the metal ions generated by the second electrode. The first functional layer comprising the photoisomerization material is provided in the light-emitting device disclosed herein. This layer can absorb harmful light and solve the problem of easy aging of the light-emitting device, and can also avoid luminescence quenching of the light-emitting device caused by metal ions, thereby extending the service life of the light-emitting device. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A cross-sectional view of a light-emitting device provided in accordance with an embodiment of the present disclosure.

[0028] Figure 2 Schematic diagram of the structural changes of the photoisomerized material in the light-emitting device provided in one embodiment of the present disclosure before and after light absorption.

[0029] Figure 3 Schematic diagram of the structural changes of the photoisomerization material in the light-emitting device provided in one embodiment of the present disclosure before and after combining with metal ions.

[0030] Figure 4 Schematic diagram of a spiropyran derivative undergoing photoisomerization and forming a complex with a metal ion.

[0031] Figure 5 Schematic diagram of another spiropyran derivative undergoing photoisomerization and forming a complex with a metal ion.

[0032] Figure 6 Schematic diagram of the structural changes of the photoisomerized material in the light-emitting device provided in one embodiment of the present disclosure before and after light absorption.

[0033] Figure 7 A cross-sectional view of a light-emitting device provided in accordance with an embodiment of the present disclosure. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present disclosure in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present disclosure without making any creative efforts shall fall within the scope of protection of the present disclosure.

[0035] OLED light-emitting devices are widely used in lighting and display equipment. The working principle of OLED is: under the action of the electric field, holes and electrons are injected by the anode and cathode respectively. After the holes and electrons migrate to the light-emitting layer, they meet to generate energy excitons, thereby exciting the light-emitting molecules in the light-emitting layer to produce visible light.

[0036] However, OLED light-emitting devices have a short service life, which greatly increases the cost of using OLED light-emitting devices. On the one hand, most of the organic materials in OLEDs are sensitive to high-energy light (such as ultraviolet light). When OLED devices are exposed to high-energy light, the high-energy light will cause the OLED to age and shorten its service life. In addition, infrared light in the environment can also accelerate the aging of the device. On the other hand, metal ions in the anode and / or cathode of the OLED may migrate into the light-emitting layer, resulting in luminescence quenching, which will also affect the service life of the OLED device. Luminescence quenching refers to the phenomenon that causes light emission to be weakened or even completely disappear.

[0037] In view of this, the present disclosure provides an OLED device, which can delay the aging of the light-emitting device and reduce the risk of luminescence quenching, thereby extending the service life of the OLED device.

[0038] Figure 1 This is a cross-sectional view of a light emitting device provided in one embodiment of the present disclosure. Figure 1 As shown, a light-emitting device 10 provided in an embodiment of the present disclosure includes a first electrode 11 , a second electrode 12 , and a light-emitting functional layer 13 located between the first electrode 11 and the second electrode 12 .

[0039] The light-emitting functional layer 13 includes a light-emitting layer 131 and a first functional layer 132. The first functional layer 132 is located between the light-emitting layer 131 and the second electrode 12. When the first and second electrodes 11 and 12 are energized, holes and electrons are injected into the first and second electrodes 11 and 12, respectively. After the holes and electrons migrate to the light-emitting layer 131, they meet and generate energy excitons, which excite the light-emitting molecules in the light-emitting layer 131 to produce visible light. The first functional layer 132 includes a photoisomerization material that absorbs light and combines with metal ions. The photoisomerization material can include a ground state structure and an isomeric structure. The ground state structure of the photoisomerization material absorbs light of a specific wavelength that is unfavorable to the light-emitting device, transforming into an isomeric structure. The ground state structure and / or the isomeric structure can combine with the metal ions that are free between the second electrode and the light-emitting layer to form a complex.

[0040] The first functional layer 132 may include a certain amount of a photoisomerizable material. When exposed to harmful light, a portion of the photoisomerizable material may transform from a ground state structure to an isomerized structure by absorbing the harmful light. Optionally, the isomerized structure may combine with metal ions to form a complex. Alternatively, another portion of the photoisomerizable material may remain in a ground state structure. The ground state structure of the photoisomerizable material may combine with metal ions to form a complex.

[0041] In one embodiment of the present disclosure, Figure 1As shown, the light-emitting device 10 is used to constitute the main structure of the sub-pixel of the display panel. When the display panel is designed to be in top emission mode, the first electrode 11 is the anode and the second electrode 12 is the cathode. The side of the light-emitting device where the cathode is located is its light-emitting side, and the first functional layer 132 is located between the cathode and the light-emitting layer 131. For example, the display panel includes an array substrate and a display functional layer located on the array substrate. The display functional layer may include a pixel defining layer and the light-emitting device 10 defined by the pixel defining layer. The first electrode 11, the light-emitting layer 131, the first functional layer 132, and the second electrode 12 in each light-emitting device 10 are sequentially stacked on the array substrate.

[0042] In another embodiment of the present disclosure, the light-emitting device 10 is used to constitute the main structure of a sub-pixel of a display panel. When the display panel is designed as a bottom emission mode, the first electrode 11 is a cathode and the second electrode 12 is an anode. The side of the light-emitting device 10 where the anode is located is its light-emitting side, and the first functional layer 132 is located between the anode and the light-emitting layer 131. For example, the display panel includes an array substrate and a display functional layer located on the array substrate. The display functional layer may include a pixel defining layer and the light-emitting device 10 defined by the pixel defining layer. The second electrode 12, the first functional layer 132, the light-emitting layer 131, and the first electrode 11 in each light-emitting device 10 are sequentially stacked on the array substrate.

[0043] Optionally, the side of the light-emitting device 10 closest to the second electrode 12 can be a light-emitting side, from which light can be emitted. The second electrode 12 can be a transmissive electrode. The first electrode 11 can be a reflective electrode. In the disclosed embodiment, the first functional layer 132 is always located on the side of the light-emitting layer 131 closest to the light-emitting side, allowing it to receive and absorb harmful ambient light.

[0044] It should be noted that in the embodiments of the present disclosure, "isomerism" refers to the phenomenon that the order of interconnection of atoms or atomic groups is the same, but the arrangement in space is different. Photoisomerization refers to the conversion of a compound from a ground state to an excited state by direct irradiation with light of a certain wavelength (e.g., ultraviolet light or infrared light) or the use of a triplet photosensitizer, thereby forming an isomeric structure from a photounstable state to a photostable state. The molecular formula of the photoisomerized material before and after light absorption may remain unchanged, and the ground state structure and isomeric structure of the photoisomerized material are isomers.

[0045] Specifically, optionally, the photoisomerization material is configured to absorb harmful light when exposed to harmful light, transforming from a ground-state structure to an isomeric structure, which can bind to metal ions. Alternatively, the photoisomerization material is configured to prevent the isomeric structure from transforming to the ground-state structure when not exposed to harmful light, i.e., the transformation between the isomeric structure and the ground-state structure is an irreversible reaction.

[0046] Optionally, the photoisomerizable material is used to transform from an isomerized structure to a ground state structure when there is no harmful light irradiation. Optionally, the ground state structure is combined with or separated from metal ions.

[0047] Among them, in a certain amount of photoisomerizable material, when exposed to harmful light, the stronger the intensity of the harmful light, the greater the amount of photoisomerizable material that changes from the ground state structure to the isomeric structure. The more metal ions diffused by the second electrode, the greater the number of isomeric structures, and the greater the number of complexes formed by the isomeric structures bound to the metal ions. The structure of the complex is relatively stable. In the absence of harmful light, under normal conditions (such as at room temperature, when the display panel is in normal use), the complex does not easily lose metal ions and change to an isomeric structure or the ground state structure. In the absence of harmful light, under normal conditions, at least part of the isomeric structure not bound to the metal ion changes to the ground state structure. If the ground state structure is separated from the metal ion, that is, the ground state structure cannot combine with the metal ion to form a complex, it is conducive to repeated use for absorbing harmful light. If the ground state structure combines with the metal ion to form a complex, it is conducive to reducing the phenomenon of luminescence quenching.

[0048] Specifically, the photoisomerizable material optionally absorbs harmful light and transforms from a ground-state structure to an isomeric structure when exposed to harmful light. This isomeric structure then binds to metal ions. In the absence of harmful light, the isomeric structure then transforms to a ground-state structure, where the ground-state structure binds to metal ions. Under normal conditions, in a given amount of photoisomerizable material, a portion of the material is in the ground-state structure and binds to metal ions to form a complex, which helps reduce luminescence quenching. In the presence of harmful light, at least a portion of the ground-state structure not bound to metal ions can transform into an isomeric structure by absorbing the harmful light, and the isomeric structure then binds to metal ions to form a complex. The reaction rate of the isomeric structure binding to metal ions is greater than that of the ground-state structure, meaning that the isomeric structure is more susceptible to metal ion binding than the ground-state structure. In the absence of harmful light, at least a portion of the isomeric structure not bound to metal ions transforms into the ground-state structure, which facilitates repeated absorption of harmful light. The amount of the photoisomerization material can be set as needed, and the first functional layer can always have three states: ground state structure, isomeric structure and complex, so as to meet the functions required for absorbing harmful light and binding metal ions.

[0049] Optionally, the harmful light may specifically include one or more of ultraviolet light and infrared light. The amount of the doped photoisomerization material may be set as needed to meet the required functions of absorbing harmful light and binding metal ions.

[0050] Figure 2 Schematic diagram of the structural change of the photoisomerized material in the light-emitting device provided in one embodiment of the present disclosure before and after light absorption. Figure 2The photoisomerization material can be an unsaturated ketone derivative. Figure 2 As shown, under specific light conditions, the photoisomerized material undergoes isomerization due to the absorption of light of a specific wavelength (e.g., ultraviolet light). After light absorption, the relative position of the C atom in the ground state structure 201 that forms a covalent bond with one of the C atoms in the C=C double bond changes, causing the O atom and N in the isomerized structure 202 to be isomerized. + The distance between the groups is relative to the O and N atoms in the ground state structure 201. + The distance between the groups is reduced. It should be understood that R1 and R2 can be any functional group and can be adaptively adjusted as needed. The ground state structure 201 can be separated from the metal ion, that is, the ground state structure 201 cannot combine with the metal ion to form a complex.

[0051] Figure 3 Schematic diagram of the structural changes of the photoisomerized material in the light-emitting device provided in one embodiment of the present disclosure before and after combining with metal ions. Figure 3 As shown, the isomeric structure 202 formed after light absorption can form a complex 203 with metal ions. n+ is a metal ion, where M is a metal and the value of n is adaptively adjusted according to the different metal elements. + The distance between the groups decreases, and the O atoms and N + The group can react with the metal ions M generated by the second electrode 12 n+ The shared electrons form a coordination bond and form complex 203. Specifically, the coordination bond is formed through N + The O atoms in the carbonyl group and the carbonyl group provide electrons, and the metal ions provide vacant orbitals. Therefore, the heterostructure 202 can bind the metal ions and prevent them from diffusing.

[0052] In this embodiment, the photoisomerized material is transformed into a heterostructure 202 after exposure to harmful light. The heterostructure 202 formed after light absorption can form a complex 203 with the metal ions generated by the second electrode 12, thereby preventing the metal ions from diffusing into the light-emitting layer 131 and causing luminescence quenching, thereby increasing the lifespan of the light-emitting device 10. In other words, the photoisomerized material of the present disclosure can not only absorb harmful light, thereby resolving the problem of susceptibility to aging of the light-emitting device 10, but also prevent luminescence quenching of the light-emitting device 10 caused by metal ions, thereby extending the lifespan of the light-emitting device 10.

[0053] The first functional layer containing a photoisomerization material can absorb harmful light, thereby slowing the aging of the light-emitting device caused by light exposure. Furthermore, the first functional layer can bind to metal ions from the second electrode, reducing the risk of luminescence quenching caused by metal ion intrusion into the light-emitting layer. Therefore, by incorporating a first functional layer containing a photoisomerization material into a light-emitting device, the technical problem of short lifespan of the light-emitting device can be resolved.

[0054] In an embodiment of the present disclosure, the photoisomerizable material undergoes cis-trans isomerism when absorbing light (eg, ultraviolet light or infrared light). When irradiated with harmful light, the photoisomerizable material undergoes cis-trans isomerism to achieve absorption of the harmful light.

[0055] Specifically, cis-trans isomerism belongs to isomerism, and cis-trans isomerism requires the following conditions:

[0056] (1) At least one bond in the molecule cannot rotate freely under normal circumstances (otherwise it will become another molecule). Specifically, the bond that cannot rotate freely can be a C=C double bond, a C=N double bond, a C=S double bond, an N=N double bond, or an alicyclic functional group that cannot rotate freely.

[0057] (2) Each atom of a non-rotatable functional group cannot have the same group attached to it and must be connected to two different atoms or atomic groups. For example, when the non-rotatable bond is a C=C double bond, each C atom in the C=C double bond is connected to a different atom or atomic group.

[0058] In this embodiment, the photoisomerization material includes a first group for isomerization. Optionally, the first group includes one or more of azobenzene, C=C, cinnamic acid and benzopyran. When the above-mentioned groups are exposed to light (such as the above-mentioned harmful light), the photoisomerization material can absorb the harmful light and can undergo cis-trans isomerization to achieve absorption of the harmful light. Optionally, after no harmful light is irradiated, the group will return to its initial state, thereby enabling reuse. For example, when the group for isomerization is a C=C double bond, the C=C double bond first becomes a transition state, then rotates, and finally becomes a new C=C double bond.

[0059] In this embodiment, the photo-isomerization material includes a second group for combining with metal ions. Optionally, the second group includes one or more of a carbonyl group, an amino group, a hydroxyl group, a benzospiropyran group, and a phosphono group.

[0060] Optionally, the group used for isomerization and the group used for combining with metal ions in the photoisomerization material are different groups.

[0061] Optionally, the group for isomerization in the photoisomerization material and the group for combining with metal ions are the same group, for example, the group may include benzospiropyran.

[0062] Optionally, the photoisomerizable material with a ground state structure combined with metal ions includes one or more groups selected from benzospiropyran and hydroxyl groups. The benzospiropyran group combines with the metal ion because the metal ion can induce the benzospiropyran group to form an isomeric structure and form a complex.

[0063] In one optional embodiment, the ground state structure and the isomeric structure of the photoisomerized material can transform into each other under specific conditions. For example, under specific conditions, such as when the light-emitting device is exposed to harmful light, at least a portion of the photoisomerized material in the first functional layer can transform from the ground state structure to the isomeric structure. The isomeric structure of the photoisomerized material binds to metal ions quickly, while the ground state structure of the photoisomerized material binds to metal ions slowly. The rate at which the isomeric structure of the photoisomerized material binds to metal ions is higher than the rate at which the ground state structure of the photoisomerized material binds to metal ions, and the efficiency of the isomeric structure binding to metal ions is higher than the efficiency of the ground state structure of the photoisomerized material binding to metal ions. Therefore, the transformation of the photoisomerized material from the ground state structure to the isomeric structure can improve the efficiency of metal ion binding while absorbing harmful light. For another example, under conditions where the light-emitting device is not exposed to harmful light and is absorbing heat, at least a portion of the isomeric structure of the photoisomerized material in the first functional layer can transform into the ground state structure. As the photoisomerized material transforms from the isomerized structure to the ground state, it absorbs heat energy, allowing it to regain the ability to absorb harmful light. The rate at which the isomerized structure of the photoisomerized material binds to metal ions is higher than the rate at which the ground state structure of the photoisomerized material binds to metal ions because the spatial configuration of the isomerized structure is more conducive to the formation of coordination bonds.

[0064] Optionally, the process of binding the heterostructure to the metal ion may be an irreversible process. After the heterostructure binds to the metal ion, it is difficult to separate under normal conditions.

[0065] Optionally, the process of the heterostructure binding to the metal ion can be a reversible process. The greater the degree of the reaction of the heterostructure binding to the metal ion relative to the degree of the reaction of the heterostructure separating from the metal ion, the better. The heterostructure binding to the metal ion can be the dominant trend.

[0066] Optionally, the process of binding the ground state structure to the metal ion may be an irreversible process. After the ground state structure binds to the metal ion, it is difficult to separate under normal conditions.

[0067] Optionally, the process of binding the ground state structure to the metal ion can be a reversible process. The greater the degree of the reaction of the ground state structure binding to the metal ion relative to the degree of the reaction of the ground state structure separating from the metal ion, the better. Binding of the ground state structure to the metal ion can be the dominant trend.

[0068] In this embodiment, the photoisomerization material may include one or more of a quaternary ammonium salt of an o-hydroxyacetophenone derivative, a quaternary ammonium salt of an α,β-unsaturated ketone derivative of 8-hydroxyquinoline, and a spiropyran derivative. The quaternary ammonium salt of an o-hydroxyacetophenone derivative, the quaternary ammonium salt of an α,β-unsaturated ketone derivative of 8-hydroxyquinoline, and the spiropyran derivative are used to absorb harmful light, such as ultraviolet light. Upon exposure to harmful light, a portion of the photoisomerization material undergoes cis-trans isomerization. Based on this, a portion of the isomerized structure can bind to metal ions. In the absence of harmful light, under normal conditions, such as room temperature, a portion of the isomerized structure not bound to the metal ions returns to its initial state, i.e., the ground state structure. A portion of the ground state structure also binds to the metal ion to form a complex. In the absence of harmful light, under normal conditions, the complex is relatively stable and does not lose metal ions, converting to an isomerized structure or ground state structure.

[0069] Alternatively, the group for isomerization and the group for binding to metal ions in the quaternary ammonium salt of an o-hydroxyacetophenone derivative or the quaternary ammonium salt of an α,β-unsaturated ketone derivative of 8-hydroxyquinoline are different groups. Alternatively, the group for isomerization and the group for binding to metal ions in a spiropyran derivative may be the same group or different groups.

[0070] Spiropyran derivatives can be used to absorb one or more of infrared and ultraviolet light. The ground state structures of at least some spiropyran derivatives can bind to metal ions under normal conditions and can dissociate from them under specific conditions. Under normal conditions, the binding of the ground state structure of the spiropyran derivative to the metal ion can be reversible, but the rate of binding to the metal ion is much greater than the rate of dissociation, with binding to the metal ion being the dominant trend. The greater the degree of binding reaction of the ground state structure of the spiropyran derivative with the metal ion relative to the degree of dissociation, the better. The isomeric structures of some spiropyran derivatives can also bind to metal ions under normal conditions and can dissociate from them under specific conditions. Under normal conditions, the binding of the isomeric structures of the spiropyran derivative to the metal ion can be reversible, but the rate of binding to the metal ion is much greater than the rate of dissociation, with binding to the metal ion being the dominant trend. The greater the degree of reaction between the isomeric structures of the spiropyran derivatives and the metal ions relative to the degree of reaction between the isomeric structures and the metal ions, the better. The isomeric structures of the spiropyran derivatives can be converted to and from their ground-state structures under specific conditions. Spiropyran derivatives are used to absorb harmful light, such as ultraviolet or infrared light. Upon exposure to harmful light, some spiropyran derivatives undergo cis-trans isomerization, transforming into isomeric structures. On this basis, some of the isomeric structures of the spiropyran derivatives can bind to metal ions. In the absence of harmful light, such as ultraviolet or infrared light, at room temperature, some of the isomeric structures of the spiropyran derivatives not bound to metal ions return to their initial state, i.e., the ground-state structure. Some of the ground-state structures will also bind to metal ions.

[0071] Figure 4 Schematic diagram of a spiropyran derivative undergoing photoisomerization and forming a complex with a metal ion. Figure 4Under ultraviolet light irradiation, a portion of ground-state structure 401 transforms into isomeric structure 402. When the ultraviolet light disappears and is irradiated with visible light (denoted by the symbol Vis) or heated (denoted by the symbol Δ), a portion of isomeric structure 402 not bound to the metal ion transforms into ground-state structure 401. A portion of isomeric structure 402 acquires the metal ion to form complex 403, while a portion of complex 403 transforms into isomeric structure 402 after losing the metal ion. At room temperature or under normal conditions, the binding of isomeric structure 402 to the metal ion is reversible, but the rate of metal ion binding is much greater than the rate of metal ion dissociation, with metal ion binding being the dominant trend. The greater the degree of metal ion binding reaction between isomeric structure 402 and the metal ion relative to the degree of metal ion dissociation reaction, the better. Upon visible light irradiation, a portion of complex 403 transforms into ground-state structure 401, while a portion of ground-state structure 401 acquires the metal ion to form complex 403. The binding of ground structure 401 to metal ions is reversible, but the rate of binding is much greater than the rate of dissociation, with binding being the dominant trend. The greater the degree of binding relative to the dissociation, the better. At room temperature or under normal conditions, a portion of isomeric structure 402 slowly transforms into ground structure 401. The photoisomerization material has little effect on the luminous efficiency of the light-emitting device. The amount of doped photoisomerization material can be adjusted to ensure the luminous efficiency of the light-emitting device.

[0072] Figure 5 This is a schematic diagram of another spiropyran derivative undergoing photoisomerization and forming a complex with a metal ion. Figure 5Under ultraviolet (UV) or infrared (IR) light, a portion of ground state structure 501 transforms into isomeric structure 502. Specifically, ground state structure 501 is a spiropyran derivative (SP), and isomeric structure 502 is a merocyanine (MC). Specifically, under UV light, electrons in ground state structure 501 are excited, and the CO bond formed by the specific carbon and oxygen atoms is broken in just a few picoseconds. The molecule then flips around the C-C bond to form isomeric structure 502 with a planar structure. After the UV light disappears, under heating, a portion of isomeric structure 502 not bound to metal ions transforms into ground state structure 501. In the absence of harmful light, at room temperature or under normal conditions, a portion of isomeric structure 502 not bound to metal ions slowly transforms into ground state structure 501. A portion of isomeric structure 502 acquires metal ions to form complexes 503, while a portion of complex 503 loses metal ions and transforms into isomeric structure 502. At room temperature or under normal conditions, the binding process between the heterostructure 502 and the metal ion can be reversible, but the rate of binding between the heterostructure 502 and the metal ion is much greater than the rate of dissociation from the metal ion, with binding to the metal ion being the dominant trend. The greater the degree of the binding reaction between the heterostructure 502 and the metal ion relative to the degree of dissociation from the metal ion, the better. A portion of the complex 503 transforms into the ground state structure 501 after absorbing heat, and a portion of the ground state structure 501 receives the metal ion to form the complex 503. At room temperature or under normal conditions, the binding process between the ground state structure 501 and the metal ion can be reversible, but the rate of binding between the ground state structure 501 and the metal ion is much greater than the rate of dissociation from the metal ion, with binding to the metal ion being the dominant trend. The greater the degree of the binding reaction between the ground state structure 501 and the metal ion relative to the degree of dissociation from the metal ion, the better. After a portion of the ground-state structure 501 in the photo-isomerized material undergoes isomerization under specific conditions, both a portion of the ground-state structure 501 and a portion of the isomeric structure 502 can bind to metal ions to form a complex 503. The isomeric structure 502 binds to metal ions faster than the ground-state structure 501. Therefore, compared to photo-isomerized materials in which the ground-state structure can separate from metal ions (i.e., the ground-state structure does not bind to metal ions), photo-isomerized materials in which both the ground-state structure 501 and the isomeric structure 502 can bind to metal ions, thereby improving the binding efficiency with metal ions while absorbing harmful light. It should be understood that R can be any functional group, and R at different positions can be the same or different, and can be adjusted as needed, which is not a limitation of the present invention.

[0073] In this way, when the light-emitting device is exposed to harmful light, the first functional layer can absorb the harmful light to slow down the aging of the light-emitting device, and bind metal ions to reduce the risk of luminescence quenching of the light-emitting device.

[0074] Figure 6 Schematic diagram of the structural change of the photoisomerized material in the light emitting device provided in one embodiment of the present disclosure before and after light absorption. Figure 6 As shown, the photoisomerized material initially has a relatively stable ground state structure 301. After exposure to harmful light, a portion of the photoisomerized material transforms from ground state structure 301 to an isomeric structure 302. After the harmful light disappears, a portion of the isomeric structure 302 not bound to metal ions returns to ground state structure 301. Upon absorbing harmful light, a portion of the photoisomerized material undergoes cis-trans isomerization, transforming into an isomeric structure. In the absence of harmful light, a portion of the isomeric structure 302 not bound to metal ions returns to the ground state structure, resuming its original state. This allows for repeated absorption of harmful light, further extending the lifespan of the light-emitting device. Figure 6 The photo-isomerization material includes a C=C bond group as an example. The photo-isomerization material may further include an acetylacetonate group. The acetylacetonate group includes a carbonyl group, and the acetylacetonate group can be used to bond with metal ions.

[0075] In at least one embodiment of the present disclosure, the wavelength of light absorbed by the photoisomerization material is different from the wavelength of light emitted by the light-emitting layer. Specifically, the wavelength of light absorbed by the photoisomerization material is less than or greater than the wavelength of light emitted by the light-emitting layer. The photoisomerization material may not absorb visible light. For example, the light absorbed by the photoisomerization material includes at least one of ultraviolet light and infrared light. Specifically, the photoisomerization material can be a material having ultraviolet or infrared isomerization functional groups. Infrared light and ultraviolet light are common and can cause aging of light-emitting devices. In one embodiment, the first functional layer including the photoisomerization material can absorb these two types of light, thereby further slowing the aging of the light-emitting device. For example, the light-emitting layer is an organic light-emitting layer, which is configured to emit red, green, blue, white, or yellow light. It should be understood that the luminous intensity and luminescent color of the light-emitting layer can be adaptively adjusted according to design requirements. The wavelength of light that can be absorbed by the photoisomerization material is smaller than the wavelength of the light emitted by the light-emitting layer. While absorbing harmful light in the environment, it can not affect the luminous intensity and luminous color of the light-emitting device. While protecting the light-emitting device, it does not affect the normal performance of the light-emitting device.

[0076] In at least one embodiment of the present disclosure, the first functional layer includes a substrate layer doped with a photo-isomerization material.

[0077] In at least one embodiment of the present disclosure, the first electrode is a cathode, the second electrode is an anode, and a substrate layer is formed on the side of the light-emitting layer close to the second electrode. The substrate layer includes one or more of a hole injection layer (HIL), a hole transport layer (HTL), and an electron blocking layer (EBL). In one embodiment, the photoisomerization material is doped in the hole transport layer. Since the thickness of the hole transport layer is greater than the thickness of the hole injection layer and the electron blocking layer, doping the photoisomerization material in the thicker hole transport layer can avoid insufficient content of the photoisomerization material and the inability to effectively absorb harmful light. The hole transport layer is formed by inkjet printing. By doping the photoisomerization material in the ink used to print the hole transport layer, the photoisomerization material can be evenly distributed in the hole transport layer. Optionally, the light-emitting functional layer also includes a second functional layer, which is located between the light-emitting layer and the first electrode. The second functional layer may include at least one of an electron transport layer, an electron injection layer, and a hole blocking layer.

[0078] In at least one embodiment of the present disclosure, the first electrode is an anode, the second electrode is a cathode, and the substrate layer is formed on the side of the light-emitting layer close to the second electrode. The substrate layer specifically includes one or more of an electron injection layer (EIL), an electron transport layer (ETL), and a hole blocking layer (HBL). In one embodiment, the photoisomerization material is doped in the electron transport layer. Since the thickness of the electron transport layer is greater than the thickness of the electron injection layer and the hole blocking layer, doping the photoisomerization material in the thicker electron transport layer can avoid insufficient content of the photoisomerization material and the inability to effectively absorb harmful light. The electron transport layer is formed by inkjet printing. By doping the photoisomerization material in the ink used to print the electron transport layer, the photoisomerization material can be evenly distributed in the electron transport layer. Optionally, the light-emitting functional layer also includes a second functional layer, which is located between the light-emitting layer and the first electrode. The second functional layer may include at least one of a hole transport layer, a hole injection layer, and an electron blocking layer.

[0079] Optionally, the light-emitting device includes an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer and a cathode stacked in sequence.

[0080] Optionally, the mass proportion of the photoisomerization material in the first functional layer is 0.01% to 10%. For example, it may be further 0.05%, 0.1%, 0.5%, 1%, 5%, 8%, etc. The photoisomerization material may specifically be a material that includes both a group for isomerization and a functional group capable of absorbing light. Specifically, the photoisomerization material may be one or more of a quaternary ammonium salt of a 2-hydroxyacetophenone derivative, a quaternary ammonium salt of an 8-hydroxyquinoline α, β-unsaturated ketone derivative, and a spiropyran derivative. The greater the mass proportion of the photoisomerization material in the first functional layer, the more light it absorbs, and the more diffused metal ions it can capture. However, if the mass proportion of the photoisomerization material in the first functional layer is too large, it will affect the electron transport characteristics of the first functional layer, thereby affecting the electrical performance and current efficiency of the device. Therefore, a mass percentage below 0.01% does not significantly improve device lifespan. While a mass percentage above 10% may improve device lifespan, it may also negatively impact device current efficiency. Current efficiency refers to the ratio of the amount of material actually deposited or dissolved on the electrode during electrolysis to the theoretically calculated amount. The present disclosure sets the mass percentage of the photoisomerized material in the first functional layer to 0.01% to 10%, improving device lifespan while avoiding adverse effects on device current efficiency.

[0081] By doping one or more functional layers of a light-emitting device with a photo-isomerization material to form a first functional layer, the device eliminates the need for a separate layer containing the photo-isomerization material, facilitating a slimmer and lighter design. Furthermore, this design eliminates the need to change the overall module design (e.g., the thickness of each layer), which helps reduce the design cost of the light-emitting device.

[0082] In at least one embodiment of the present disclosure, the first electrode is an anode, and the light-emitting device may further include a second functional layer located between the light-emitting layer and the first electrode. The second functional layer may include a hole injection layer (HOL), a hole transport layer (HTL), and an electron blocking layer (EBL).

[0083] Figure 7 This is a cross-sectional view of a light emitting device provided by an embodiment of the present disclosure. Taking the first electrode 11 as an anode and the second electrode 12 as a cathode as an example, Figure 7As shown, the light-emitting device 10 includes, stacked from bottom to top, a first electrode 11, a second functional layer 133, a light-emitting layer 131, a first functional layer 132, a second electrode 12, and a coupling layer (CPL) 14. The first functional layer 132 includes an electron transport layer 1321 and an electron injection layer 1322; the second functional layer 133 includes a hole transport layer 1331 and an interlinked layer (IL) 1332.

[0084] Combine Figure 7 At least one embodiment of the present disclosure provides a method for preparing a light-emitting device, as follows:

[0085] Step S100: providing a first electrode 11.

[0086] Step S200: Prepare the hole transport layer 1331. On the first electrode 11, a 1.5% by mass solution of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS) dissolved in a 5% by volume:95% isopropyl alcohol and water mixture was printed by inkjet printing. After printing, the layer was baked in air at 200°C for 10 minutes.

[0087] Step S300: Prepare cross-linked layer 1332. A cross-linked material (such as ethoxylated polyethyleneimine (PEIE)) dissolved in xylene solution at a mass ratio of 1% is printed by inkjet printing. After printing, the cross-linked layer 1332 is baked at 170°C in nitrogen for 1 hour to complete the preparation of cross-linked layer 1332.

[0088] Step S400: Prepare the light-emitting layer 131. A 2% by mass polymer light-emitting material (a dendrimer composed of Firpic and 2,2'-dimethylbiphenyl in a mass ratio of 1:9) dissolved in a xylene solution is printed by inkjet printing. After printing, the dendrimer is baked in nitrogen at 150°C for 10 minutes to complete the preparation of the light-emitting layer 131.

[0089] Step S500: Prepare the electron transport layer 1321. Print the electron transport layer 1321 material (e.g., a photoisomerization material (a quaternary ammonium salt of an α,β-unsaturated ketone derivative of 8-hydroxyquinoline) and an electron transport material (2,7-bis(diphenylphosphoryl)-9,9'-spirobifluorene) in a mass ratio of 1:99) dissolved in a mixed solution of n-butanol and 1,2-propylene glycol in a volume ratio of 3:7 by inkjet printing. After printing, vacuum operation is performed at 50°C, and then baked at 180°C in nitrogen for 30 minutes to complete the preparation of the electron transport layer 1321. The comparative example does not dope the photoisomerization material, while the embodiment does dope the photoisomerization material.

[0090] Step S600: Prepare the electron injection layer 1322. Prepare lithium fluoride (LiF) with a thickness of 10 nm by vacuum evaporation.

[0091] Step S700: Prepare the second electrode 12. Specifically, prepare a 10 nm magnesium-silver alloy by vacuum evaporation.

[0092] Step S800: preparing the photoelectric coupling layer 14. Specifically, the photoelectric coupling layer 14 is formed by vacuum evaporation of a 60 nm photoelectric coupling layer material.

[0093] Step S900: performing cover packaging.

[0094] The light emitting device of this embodiment including the photoisomerization material and the light emitting device of the comparative example not including the photoisomerization material were tested under the same conditions. The specific testing method is as follows:

[0095] Test 1, the effect of inhibiting metal ion diffusion on lifespan:

[0096] The prepared device was placed in a darkroom and powered by a Keithley 3700. The output current was sufficient to achieve an initial brightness of 1000 nits, and the current was subsequently maintained constant. A PR705 spectrometer within the darkroom continuously monitored the visible light spectrum. Under these conditions, the brightness of the comparative example's light-emitting device decayed to 900 nits in 290 hours, while the brightness of the light-emitting device of this embodiment decayed to 900 nits in 418 hours. The lifespan of the light-emitting device of this embodiment was approximately 44% longer than that of the light-emitting device of the comparative example.

[0097] Test 2: Effect of inhibiting metal ion diffusion and absorbing ultraviolet light on lifespan:

[0098] The prepared light-emitting device was placed in a darkroom equipped with a UV lamp with a main emission wavelength of 254nm. The device was powered by a Keithley 3700, with an output current that resulted in an initial brightness of 1000 nits. The current was then maintained constant. The UV lamp remained on during the lifespan test. Under these conditions, the brightness of the comparative example's light-emitting device decayed to 900 nits in 88 hours, while the brightness of the light-emitting device of this embodiment decayed to 900 nits in 177 hours. The lifespan of the light-emitting device of this embodiment was improved by approximately 101% compared to that of the light-emitting device of the comparative example.

[0099] In this embodiment, the photoisomerization material can extend the life of the light-emitting device by more than 40% by inhibiting metal ion diffusion. By absorbing ultraviolet and infrared light, the photoisomerization material can extend the life of the light-emitting device by more than 100%. Therefore, the light-emitting device of this embodiment can significantly extend its life.

[0100] In this embodiment, the first electrode 11 can be a reflective electrode, and the second electrode 12 can be a metal layer with a designed thickness to be transparent or translucent. Specifically, the side of the light-emitting device facing the second electrode is its light-emitting side, and accordingly, this side is also the side of the light-emitting device illuminated by external ambient light.

[0101] In this embodiment, the light-emitting device can be prepared by inkjet printing or evaporation. Specifically, the crosslinking layer, the light-emitting layer, and the electron transport layer are formed by solution inkjet printing, and the electron injection layer, the second electrode, and the photoelectric coupling layer are formed by evaporation.

[0102] Specifically, the first electrode 11 may be made of a conductive material such as a conductive metal oxide, such as zinc oxide, indium oxide, tin oxide, indium tin oxide (ITO), indium zinc oxide (IZO), or fluorine-doped tin oxide.

[0103] Specifically, the material of the second electrode 12 can be a conductive material such as a metal, a conductive metal oxide, a conductive polymer, or a combination thereof. Specifically, the material of the second electrode 12 can be a metal or an alloy thereof, such as aluminum, magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, silver, gold, platinum, tin, lead, cesium, or barium. The material of the second electrode 12 can also be a multilayer structure, but is not limited thereto. It should be noted that when the thickness of the film layer composed of the metal is relatively small (for example, as small as a few hundred angstroms or less), the film layer will appear transparent.

[0104] At least one embodiment of the present disclosure provides a display panel comprising a display area in which a plurality of light-emitting devices according to the aforementioned embodiments are disposed. For example, the display panel may further comprise the aforementioned array substrate, on which the light-emitting devices are arrayed to form sub-pixels of the display panel. Specifically, the display panel may be a display screen for electronic products such as smartphones, computer monitors, game consoles, and televisions.

[0105] The light-emitting device provided according to any embodiment of the present disclosure and the display panel provided according to the embodiment of the present disclosure are based on the same inventive concept and have corresponding film layer structures and beneficial effects. Details not fully described in the embodiment of the display panel can be found in the embodiment of the light-emitting device and will not be repeated here.

[0106] The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the present disclosure should be included in the scope of protection of the present disclosure.

Claims

1. A light emitting device, characterized in that: The device comprises a first electrode, a second electrode and a light-emitting functional layer located between the first electrode and the second electrode, wherein: The light-emitting functional layer includes a light-emitting layer and a first functional layer, wherein the first functional layer is located between the light-emitting layer and the second electrode, and the first functional layer includes a photoisomerization material, wherein the photoisomerization material is used to absorb light and combine with metal ions; The photoisomerization material is used to absorb harmful light when exposed to harmful light, and change from a ground state structure to an isomerized structure. The isomerized structure combines with the metal ions to prevent the metal ions from diffusing into the light-emitting layer to cause luminescence quenching.

2. The light emitting device according to claim 1, wherein The photoisomerization material is used to change from an isomerized structure to a ground state structure when there is no harmful light irradiation, and the ground state structure is combined with or separated from the metal ion; The photoisomerizable material undergoes cis-trans isomerization upon absorbing the harmful light.

3. The light emitting device according to claim 2, characterized in that The harmful light has a wavelength different from a wavelength of light emitted by the light emitting layer.

4. The light emitting device according to claim 3, characterized in that The harmful light includes at least one of ultraviolet light and infrared light.

5. The light emitting device according to any one of claims 2 to 4, characterized in that: The photo-isomerization material includes a first group for isomerization and / or a second group for combining with the metal ion. The first group includes at least one of azobenzene, C=C, cinnamic acid and benzospiropyran, The second group includes at least one of a carbonyl group, an amino group, a hydroxyl group, a benzospiropyran group, and a phosphono group.

6. The light emitting device according to claim 5, characterized in that The photoisomerization material includes at least one of a quaternary ammonium salt of an o-hydroxyacetophenone derivative, a quaternary ammonium salt of an 8-hydroxyquinoline α, β unsaturated ketone derivative, and a spiropyran derivative.

7. The light emitting device according to any one of claims 1 to 4, characterized in that: The first electrode is a reflective electrode, and the second electrode is a transmissive electrode.

8. The light emitting device according to claim 7, characterized in that The first functional layer includes a substrate layer doped with the photo-isomerization material; The first electrode is an anode, the second electrode is a cathode, and the substrate layer includes at least one of an electron injection layer, an electron transport layer, and a hole blocking layer; Alternatively, the first electrode is a cathode, the second electrode is an anode, and the substrate layer includes at least one of a hole injection layer, a hole transport layer, and an electron blocking layer.

9. The light emitting device according to claim 8, characterized in that The mass proportion of the photo-isomerization material in the first functional layer is 0.01% to 10%.

10. A display panel, characterized in that: The device comprises a display area, in which a plurality of light-emitting devices according to any one of claims 1 to 9 are arranged.

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