CN115433241B - Phosphorescent material, light-emitting device, display substrate and display device - Google Patents
Phosphorescent material, light-emitting device, display substrate and display device Download PDFInfo
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Abstract
The invention discloses a phosphorescent material, a light emitting device, a display substrate and a display device, wherein the phosphorescent material comprises: an iridium (III) complex, wherein the iridium (III) complex is provided with a first ligand and a second ligand, the first ligand is provided with a first heterocyclic structure and a multi-ring structure connected with the first heterocyclic structure, and a first heteroatom and the multi-ring structure in the first heterocyclic structure are connected with the iridium (III) through chemical bonds; the second ligand comprises a second heterocyclic structure and a first benzene ring structure connected with the second heterocyclic structure, wherein a second heteroatom in the second heterocyclic structure and the first benzene ring structure are connected with iridium (III) through chemical bonds, the first heteroatom comprises one of B, N, P, and the second heteroatom comprises at least one of B, N, P, O, S, se. The phosphorescent material is applied to the light emitting device, and a device with a high color gamut, high efficiency, and long lifetime can be realized.
Description
Technical Field
The invention belongs to the technical field of display, and particularly relates to a phosphorescent material, a light emitting device, a display substrate and a display device.
Background
With the wide attention of Organic Light Emitting Diodes (OLEDs), many developments have been made in the research of orange, yellow, green, blue and white OLEDs, but red light, especially deep red light, has problems of low quantum efficiency, low color purity, short lifetime, and the like in addition to the energy gap law. In view of the above problems, researchers have focused on improving the external quantum efficiency and lifetime of devices and narrowing the full width at half maximum (FWHM) in order to meet the application requirements of red OLEDs on high color gamut, high brightness, and high contrast display panels. Among them, EQE is mainly an influence of the exciton utilization, photoluminescence quantum yield (PLQY), carrier recombination efficiency, and light extraction efficiency; the lifetime is mainly affected by the device structure and intrinsic properties of the material; the half-width is mainly affected by the excimer characteristics and the thickness of the device.
At present, although some red phosphorescent materials can improve the luminous efficiency of a red light OLEDs device, red phosphorescence with good color purity is difficult to obtain due to the extremely wide half-peak width, the display effect is affected, and the application of the red phosphorescent materials in the display field is limited.
Disclosure of Invention
An object of an embodiment of the present invention is to provide a phosphorescent material, a light emitting device, a display substrate, and a display apparatus, which are used for solving the problem that the existing luminescent material is difficult to obtain phosphorescence with good color purity.
In a first aspect, embodiments of the present invention provide a phosphorescent material comprising:
An iridium (III) complex, wherein the iridium (III) complex is provided with a first ligand and a second ligand, the first ligand is provided with a first heterocyclic structure and a multi-ring structure connected with the first heterocyclic structure, and a first heteroatom in the first heterocyclic structure is connected with the multi-ring structure and the iridium (III) through chemical bonds;
the second ligand comprises a second heterocyclic structure and a first benzene ring structure connected with the second heterocyclic structure, wherein a second heteroatom in the second heterocyclic structure is connected with the first benzene ring structure and iridium (III) through chemical bonds, the first heteroatom comprises one of B, N, P, and the second heteroatom comprises at least one of B, N, P, O, S, se.
Wherein the multi-ring structure comprises a second benzene ring structure connected with the first heterocyclic structure, and one carbon atom of the second benzene ring structure is connected with the first hetero atom and the iridium (III) through coordination bonds.
Wherein a third heteroatom is structurally connected to the first benzene ring, the third heteroatom and iridium (III) are connected through a coordination bond, and the third heteroatom comprises one of O, S, se.
Wherein the iridium (III) complex has the structural formula:
Wherein R 1～R9 is independently selected from the group consisting of H, D, F, cl, br, I, -CN, -NO 2、-CF3、-OH、 -SH、-NH2、C1～C30, C 1～C30, C 3～C30, C 1～C30, C 1～C30, C 6～C60, C 6～C60, C 5～C60, C 5～C60, and Si, ge, B, N, P, O, S and Se, respectively, wherein the heteroatoms of the heteroaryl and heteroaromatic groups are independently selected from at least one of Si, ge, B, N, P, O, S and Se;
R 10～R20 is independently selected from any one of H, C 1-C4 alkyl, C 1-C4 haloalkyl, aryl, condensed ring group, anilino, carbazolyl and fluorenyl respectively;
x is N, B or P;
Y is selected from O, S, se, N (Ri), B (Rj), P (Rk) = O, C = O, C = S, S = O, SO 2,
P= O, P =s, ri, rj, rk are independently selected from H, D, a linear hydrocarbon group of substituted or unsubstituted C 1～C30, a branched hydrocarbon group of substituted or unsubstituted C 1～C30, a cycloalkyl group of substituted or unsubstituted C 3～C30, an aryl group of substituted or unsubstituted C 6～C60, a heteroaryl group of substituted or unsubstituted C 5～C60, a heteroatom of the heteroaryl group is independently selected from at least one of Si, ge, B, N, P, O, S and Se; a represents a first heterocyclic structure.
Wherein A is selected from five-membered heterocycle or six-membered heterocycle containing at least one N.
Wherein, the structural formula of A is:
Wherein Z is N or C (Rm), rm is selected from H, D, F, cl, br, I, -CN, -NO 2、-CF3、 -OH、-SH、-NH2、C1～C30 straight-chain hydrocarbon or deuterated straight-chain hydrocarbon, C 1～C30 branched-chain hydrocarbon or deuterated branched-chain hydrocarbon, C 3～C30 cycloalkyl, C 1～C30 alkoxy, C 1～C30 alkylthio, C 6～C60 aryl, C 6～C60 aryl ether, C 5～C60 heteroaryl or C 5～C60 heteroaryl ether, and the heteroatoms of the heteroaryl or heteroaryl ether are independently selected from at least one of Si, ge, B, N, P, O, S and Se.
Wherein the iridium (III) complex has the structural formula:
Wherein L comprises (CH 2)n、C(CH3)2, O, S or Se.
Wherein the structural formula of the iridium (III) complex is selected from any one of structural formulas (Ir-1) - (Ir-8):
wherein, still include:
A host light emitting material in which the phosphorescent material is doped.
In a second aspect, an embodiment of the present invention provides a light emitting device including:
A light emitting unit including a light emitting layer including the material described in the above embodiment.
Wherein the light emitting device includes:
The light-emitting layer is arranged between the first electrode and the second electrode;
the light-emitting device comprises a first carrier layer and a second carrier layer, wherein the first carrier layer is arranged between the first electrode and the light-emitting layer, and the second carrier layer is arranged between the second electrode and the light-emitting layer.
Wherein the light emitting unit includes:
the light-emitting layer comprises a first light-emitting layer and a second light-emitting layer, and the charge-generating layer is arranged between the first light-emitting layer and the second light-emitting layer.
Wherein the light emitting unit includes:
A first electron transport layer and a first hole transport layer, the first light emitting layer being disposed between the first electron transport layer and the first hole transport layer, the first hole transport layer being disposed between the first light emitting layer and the charge generating layer;
the second light-emitting layer is arranged between the second electron transport layer and the second hole transport layer, and the second electron transport layer is arranged between the second light-emitting layer and the charge generation layer.
Wherein the wavelength of light emitted by the first light emitting layer is different from the wavelength of light emitted by the second light emitting layer.
The light emitting device comprises a plurality of light emitting units, and the wavelengths of light emitted by at least two light emitting units in the light emitting units are different.
In a third aspect, an embodiment of the present invention provides a display substrate including the light emitting device described in the above embodiment.
In a fourth aspect, an embodiment of the present invention provides a display device, including the display substrate described in the foregoing embodiment.
The phosphorescent material of the embodiment of the invention comprises: an iridium (III) complex, wherein the iridium (III) complex is provided with a first ligand and a second ligand, the first ligand is provided with a first heterocyclic structure and a multi-ring structure connected with the first heterocyclic structure, and a first heteroatom in the first heterocyclic structure is connected with the multi-ring structure and the iridium (III) through chemical bonds; the second ligand comprises a second heterocyclic structure and a first benzene ring structure connected with the second heterocyclic structure, wherein a second heteroatom in the second heterocyclic structure is connected with the first benzene ring structure and iridium (III) through chemical bonds, the first heteroatom comprises one of B, N, P, and the second heteroatom comprises at least one of B, N, P, O, S, se. The hetero atoms are embedded in the ligand of the iridium (III) complex, and the hetero atoms can have different electron donating or electron withdrawing characteristics, so that the electron or hole injection barrier can be reduced, a multiple resonance effect can be formed, HOMO and LUMO can be effectively separated on different atoms or units, the good rigid structure can reduce molecular vibration, the half-peak width is narrower, red phosphorescence with better color purity can be obtained, the display effect is improved, and the application of the iridium (III) complex in the display field is facilitated. The iridium (III) complex can simultaneously utilize singlet (25%) and triplet (75%) excitons due to the heavy atomic effect, so that the theoretical exciton utilization rate reaches 100%, the strong Spin Orbit Coupling (SOC) effect (SOC constant xi=3909 cm < -1 >) enables radiation transition to be strong, the microsecond phosphorescence life can obviously promote intersystem crossing, the photoluminescence quantum yield (PLQY) can be improved, the External Quantum Efficiency (EQE) of a red light OLEDs device can be improved by using the iridium (III) complex material, and the iridium (III) complex can be applied to a light-emitting device, so that a display panel with high color gamut, high efficiency and long service life can be realized, and the application requirements of the red light OLEDs can be met.
Drawings
Fig. 1 is a schematic structural view of a light emitting device according to an embodiment of the present invention;
fig. 2 is a schematic structural view of a light emitting device according to another embodiment of the present invention;
Fig. 3 is a schematic structural view of a light emitting device according to still another embodiment of the present invention;
fig. 4 is a schematic structural view of a light emitting device according to still another embodiment of the present invention.
Reference numerals
A light emitting layer 10;
A first light emitting layer 11; a second light emitting layer 12;
A red light emitting layer 111; a green light emitting layer 112;
A red light emitting layer 121; a green light emitting layer 122;
A first electrode 21; a second electrode 22;
A first carrier layer 31; a second carrier layer 32;
a first electron transport layer 41; a second electron transport layer 42;
A cathode 43; an anode 44; a hole injection layer 45;
A first hole transport layer 51; a second hole transport layer 52;
A hole transport layer 511; a hole transport layer 512;
A hole transport layer 521; a hole transport layer 522; a hole transport layer 523;
a charge generation layer 60; an N-type charge generation layer 61; p-type charge generation layer 62.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The terms first, second and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that embodiments of the invention may be practiced otherwise than as specifically illustrated or described herein. Furthermore, in the description and claims, "and/or" means at least one of the connected objects, and the character "/", generally means that the associated object is an "or" relationship.
The following describes in detail the phosphorescent material provided by the embodiment of the present invention through specific embodiments and application scenarios thereof with reference to fig. 1 to 4.
The phosphorescent material of the embodiment of the invention comprises: an iridium (III) complex having a first ligand and a second ligand therein, the first ligand having a first heterocyclic structure and a polycyclic structure attached to the first heterocyclic structure, the first heteroatom in the first heterocyclic structure and the polycyclic structure being attached to iridium (III) by a chemical bond, e.g., the first heteroatom in the first heterocyclic structure and the polycyclic structure and iridium (III) being attached by a coordination bond; the second ligand includes a second heterocyclic structure and a first benzene ring structure connected with the second heterocyclic structure, wherein a second heteroatom in the second heterocyclic structure is connected with the first benzene ring structure and iridium (III) through chemical bonds, for example, a second heteroatom in the second heterocyclic structure is connected with the first benzene ring structure and iridium (III) through coordination bonds, the first heteroatom can comprise one of B, N, P, and the second heteroatom can comprise at least one of B, N, P, O, S, se. For example, a benzene ring structure may be included in the multi-ring structure, the first heteroatom may be N, and the second heteroatom may be N or S.
The hetero atoms are embedded in the ligand of the iridium (III) complex, and the hetero atoms can have different electron donating or electron withdrawing characteristics, so that the injection barrier of electrons or holes can be reduced, a multiple resonance effect can be formed, HOMO and LUMO are effectively separated on different atoms or units, non-radiative transition is reduced, radiative transition is increased, and high PLQY is realized; the good rigid structure can also reduce molecular vibration, so that the half-peak width is narrower, red phosphorescence with better color purity can be obtained, the display effect is improved, and the application of the red phosphorescence in the display field is facilitated. The iridium (III) complex can simultaneously utilize singlet (25%) and triplet (75%) excitons due to the heavy atomic effect, so that the theoretical exciton utilization rate reaches 100%, the strong Spin Orbit Coupling (SOC) effect (SOC constant xi=3909 cm -1) enables radiation transition to be strong, the microsecond phosphorescence life can obviously promote intersystem crossing, the photoluminescence quantum yield (PLQY) can be improved, the External Quantum Efficiency (EQE) of a red light OLEDs device can be improved by using the iridium (III) complex material, the iridium (III) complex can be applied to a light-emitting device, a display panel with high color gamut, high efficiency and long service life can be realized, the application requirements of the red light OLEDs can be met, and the iridium (III) complex material can be applied to full-color and white light display with high resolution.
In some embodiments, the multi-ring structure includes a second benzene ring structure attached to the first heterocyclic structure, one carbon atom of the second benzene ring structure being attached to the first heteroatom and the iridium (III) via a coordination bond. The multi-ring structure may include a plurality of second benzene ring structures, wherein one carbon atom of one second benzene ring structure may be connected with iridium (III) through a coordination bond.
Optionally, a third heteroatom is attached to the first benzene ring structure, the third heteroatom and the iridium (III) are connected by a coordination bond, and the third heteroatom comprises one of O, S, se. For example, a third heteroatom may be attached to one carbon atom of the first benzene ring structure, the third heteroatom may be an O atom, and the iridium (III) may be attached via a coordinate bond.
Alternatively, the iridium (III) complex may have the structural formula:
Wherein R 1～R9 is independently selected from the group consisting of H, D, F, cl, br, I, -CN, -NO 2、-CF3、-OH、 -SH、-NH2、C1～C30, C 1～C30, C 3～C30, C 1～C30, C 1～C30, C 6～C60, C 6～C60, C 5～C60, C 5～C60, and Si, ge, B, N, P, O, S and Se, respectively, wherein the heteroatoms of the heteroaryl and heteroaromatic groups are independently selected from at least one of Si, ge, B, N, P, O, S and Se;
R 10～R20 is independently selected from any one of H, C 1-C4 alkyl, C 1-C4 haloalkyl, aryl, condensed ring group, anilino, carbazolyl and fluorenyl respectively;
x is N, B or P;
Y is selected from O, S, se, N (Ri), B (Rj), P (Rk) = O, C = O, C = S, S = O, SO 2,
P= O, P =s, ri, rj, rk may be independently selected from H, D, a linear hydrocarbon group of substituted or unsubstituted C 1～C30, a branched hydrocarbon group of substituted or unsubstituted C 1～C30, a cycloalkyl group of substituted or unsubstituted C 3～C30, an aryl group of substituted or unsubstituted C 6～C60, a heteroaryl group of substituted or unsubstituted C 5～C60, a heteroatom of the heteroaryl group being independently selected from at least one of Si, ge, B, N, P, O, S and Se; a represents a first heterocyclic structure.
Alternatively, a may be selected from five-membered or six-membered heterocycles containing at least one N.
Alternatively, the structural formula of a may be:
Wherein Z is N or C (Rm), rm can be independently selected from H, D, F, cl, br, I, -CN, -NO 2、-CF3、-OH、-SH、-NH2、C1～C30 linear or deuterated linear, C 1～C30 branched or deuterated branched, C 3～C30 cycloalkyl, C 1～C30 alkoxy, C 1～C30 alkylthio, C 6～C60 aryl, C 6～C60 aryl ether, C 5～C60 heteroaryl or C 5～C60 heteroaryl ether, and the heteroatoms of the heteroaryl or heteroaryl ether are independently selected from at least one of Si, ge, B, N, P, O, S and Se.
In some embodiments, the iridium (III) complex may have the structural formula:
Wherein L comprises (CH 2)n、C(CH3)2, O, S or Se.
Alternatively, the structural formula of the iridium (III) complex may be selected from any one of structural formulas (Ir-1) to (Ir-8):
In the application process, the same iridium (III) complex can be selected, and a plurality of iridium (III) complexes can be selected, for example, the structural formula (Ir-1) can be selected, the structural formula (Ir-2) and the structural formula (Ir-5) can be selected, and the iridium (III) complex can be specifically selected according to actual conditions. The ligand containing benzimidazole structure has strong electron transfer promotion capability, strong chelating capability with N, O formed by phenol, and long bond length The N, O formed in the structural formulas (Ir-1) - (Ir-8) has strong chelating ability and strong molecular stability.
Optionally, the material further comprises:
A host light emitting material in which the phosphorescent material is doped.
The host light emitting material may include n-type and p-type host materials, the doping ratio of the n-type and p-type host materials may be 1:1, and changing the doping ratio thereof may further fine tune the carrier recombination efficiency. The phosphorescent material can be suitable for doping type organic electroluminescent devices and can be doped in an exciplex host material. The red light device has the advantages of simple structure, high color gamut, high efficiency, weak efficiency roll-off at high current density, low starting voltage and driving voltage and long service life. The host luminescent material may be an exciplex host material, that is, an n-type molecule with a strong electron donating ability and a p-type molecule with a strong electron withdrawing ability, the exciplex host may include αnpd (p-type) and NBPhen (n-type), and the ratio of αnpd to NBPhen may be selected according to the actual situation, for example, the ratio of αnpd to NBPhen may be 1:1. The host luminescent material adopts an exciplex host material, the lowest triplet state energy of the host material is higher than that of a phosphorescent molecular material, the energy levels of the devices are matched, and the device is slowly deteriorated due to the balance of carrier transmission. The host luminescent material can be an exciplex host material, the exciplex host material can improve carrier mobility and capture rate, can regulate and control carrier balance concentration according to the doping ratio of p-type and n-type materials, and can efficiently transfer energy to iridium (III) complex guest materials through charge transfer transition; on the other hand, not only can two molecules be designed and obtained more simply, but also the diversity selectivity of the host material can be increased. Therefore, the adoption of the exciplex body material can effectively improve the carrier recombination efficiency and reduce the degradation speed of the device, thereby improving the performance and the service life of the device.
An embodiment of the present invention provides a light emitting device, as shown in fig. 1 to 4, including:
a light emitting unit including the light emitting layer 10, the light emitting layer 10 including the materials described in the above embodiments. The light-emitting device with the materials described in the above embodiments can realize a high color gamut, high efficiency and long lifetime, and can meet the application requirements of the light-emitting device.
In some embodiments, a light emitting device includes: the first electrode 21, the second electrode 22, the first carrier layer 31, and the second carrier layer 32, and the light-emitting layer 10 is disposed between the first electrode 21 and the second electrode 22. The first carrier layer 31 is disposed between the first electrode 21 and the light emitting layer 10, and the second carrier layer 32 is disposed between the second electrode 22 and the light emitting layer 10. For example, as shown in fig. 1, the first electrode 21 may be a cathode, the second electrode 22 may be an anode, and the first carrier layer 31 may include at least one of an electron injection layer 311 and an electron transport layer 312, and in the case where the first carrier layer 31 includes the electron injection layer 311 and the electron transport layer 312, the electron transport layer 312 is disposed close to the light emitting layer 10; the second carrier layer 32 may include at least one of a hole injection layer 321 and a hole transport layer 322, and in the case where the second carrier layer 32 includes the hole injection layer 321 and the hole transport layer 322, the hole transport layer 322 is disposed close to the light emitting layer 10.
A hole blocking layer 33 may be disposed between the electron transport layer 312 and the light emitting layer 10, and the hole blocking layer 33 may block holes from the anode at the interface of the light emitting layer, thereby improving the probability of recombination of electrons and holes at the interface of the light emitting layer and increasing the light emitting efficiency of the device. An electron blocking layer may be disposed between the hole transport layer 322 and the light emitting layer 10, and the electron blocking layer may block electrons from the cathode at the light emitting layer interface, increasing the concentration of electrons at the light emitting layer interface.
Alternatively, as shown in fig. 2 to 3, the light emitting unit includes: the charge generation layer 60, the charge generation layer 60 may be a charge generation layer formed by mixing a p-type organic semiconductor and an n-type organic semiconductor. The light emitting layer 10 includes a first light emitting layer 11 and a second light emitting layer 12, and the charge generating layer 60 is disposed between the first light emitting layer 11 and the second light emitting layer 12. Under the action of an external electric field, the charge generation layer 60 can generate and separate charges, the charges can enter the first light-emitting layer 11 and the second light-emitting layer 12, the charges can be combined with charges injected from electrodes to form a plurality of pairs of excitons, and the excitons are radiated and attenuated to release photons, namely light is emitted, so that the high efficiency, the long service life and the like of the laminated OLED device are realized. The wavelengths of the light emitted from the first light emitting layer 11 and the second light emitting layer 12 may be the same or different, and may be selected according to practical situations.
Alternatively, the light emitting unit may include: the first electron transport layer 41, the first hole transport layer 51, the second electron transport layer 42 and the second hole transport layer 52, the first light emitting layer 11 is disposed between the first electron transport layer 41 and the first hole transport layer 51, and the first hole transport layer 51 is disposed between the first light emitting layer 11 and the charge generating layer 60; the second light emitting layer 12 is disposed between the second electron transport layer 42 and the second hole transport layer 52, and the second electron transport layer 42 is disposed between the second light emitting layer 12 and the charge generation layer 60. The charge generation layer 60 may include a P-N junction structure composed of an N-type charge generation layer 61 and a P-type charge generation layer 62, the N-type charge generation layer 61 being disposed adjacent to the second electron transport layer 42, the P-type charge generation layer 62 being disposed adjacent to the first hole transport layer 51. Holes generated by the charge generation layer 60 may enter the first light emitting layer 11, and electrons generated by the charge generation layer 60 may enter the second light emitting layer 12, so that the light emitting efficiency of the device is higher.
As shown in fig. 2, the first light emitting layer 11 may emit blue light, the second light emitting layer 12 may emit red light and green light, the second light emitting layer 12 may include a red light emitting layer 121 and a green light emitting layer 122, the red light emitting layer 121 and the green light emitting layer 122 may be stacked, and the phosphorescent material in the present invention may be applied to the red light emitting layer 121, and may be mixed into white light by red light, green light, and blue light.
As shown in fig. 3, the first light emitting layer 11 may emit red light and green light, the second light emitting layer 12 may emit blue light, the first light emitting layer 11 may include a red light emitting layer 111 and a green light emitting layer 112, the red light emitting layer 111 and the green light emitting layer 112 may be stacked, and the phosphorescent material in the present invention may be applied to the red light emitting layer 111, and may be mixed into white light by red light, green light, and blue light. A cathode 43 may be disposed on a side of the first electron transport layer 41 remote from the first light emitting layer 11, and an anode 44 may be disposed on a side of the second hole transport layer 52 remote from the second light emitting layer 12. An electron injection layer may be disposed between the first electron transport layer 41 and the cathode 43, and a hole injection layer 45 may be disposed between the second hole transport layer 52 and the anode 44.
Alternatively, the wavelengths of the light emitted from the first light emitting layer 11 and the second light emitting layer 12 are different, and the light emitted from the first light emitting layer 11 and the second light emitting layer 12 may be mixed into light of different wavelengths so as to emit light of a desired color.
Optionally, the light emitting device includes a plurality of light emitting units, and at least two of the plurality of light emitting units emit light having different wavelengths. For example, the light emitting device may include three light emitting units, each of which emits light having a different wavelength. Of the three light emitting units, the first light emitting layer 11 and the second light emitting layer 12 in one light emitting unit emit red light, the first light emitting layer 11 and the second light emitting layer 12 in one light emitting unit emit green light, and the first light emitting layer 11 and the second light emitting layer 12 in one light emitting unit emit blue light.
As shown in fig. 4, each of the three light emitting units may include: first electron transport layer 41 (ETL), first hole transport layer 51, second electron transport layer 42 (ETL 1), and second hole transport layer 52, first light-emitting layer 11 is disposed between first electron transport layer 41 and first hole transport layer 51, and first hole transport layer 51 is disposed between first light-emitting layer 11 and charge generation layer 60; the second light emitting layer 12 is disposed between the second electron transport layer 42 and the second hole transport layer 52, and the second electron transport layer 42 is disposed between the second light emitting layer 12 and the charge generation layer 60. The charge generation layer 60 may include an N-type charge generation layer 61 (N-CGL) and a P-type charge generation layer 62 (P-CGL), the N-type charge generation layer 61 being disposed adjacent to the second electron transport layer 42, the P-type charge generation layer 62 being disposed adjacent to the first hole transport layer 51. A Cathode 43 (Cathode) may be disposed on a side of the first electron transport layer 41 away from the first light emitting layer 11, and an anode may be disposed on a side of the second hole transport layer 52 away from the second light emitting layer 12.
An electron injection layer 45 (EIL) may be disposed between the first electron transport layer 41 and the cathode 43, and the cathode 43 may be encapsulated by an encapsulation layer 46 (CPL). The first hole transport layer 51 may include a hole transport layer 511 (HTL 4) and a hole transport layer 512 (HTL 3) that are stacked. The three light emitting units may share the second hole transport layer 52, the second hole transport layer 52 may include a hole transport layer 521 (HTL 1) and a hole transport layer 522 (HTL 2) stacked, the hole transport layer 522 may be disposed near the second light emitting layer 12, a hole transport layer 523 (P-HTL) may be disposed on a side of the hole transport layer 521 away from the hole transport layer 522, and the hole transport layer 523 may be P-doped.
Taking the following material in the structural formula (Ir-1) as an example, a specific preparation process can be as follows:
1mol of 2-bromo-1, 3-difluoro-5-iodobenzene, 4mol of K 2CO3 and 4mol of phenol are respectively filled into a reaction bottle, then 100mL of N-methylpyrrolidone is added, the mixture is reacted for 24 hours under the atmosphere of N 2 and the temperature of 135 ℃, water is added and filtration is carried out to obtain a filter cake, and the filter cake is dried and CH 2Cl2 is recrystallized to obtain an intermediate (A1);
1mol of the intermediate (A1), 0.1mol of Pd (PPh 3)4 and 1mol of 2- (tributylstannyl) pyridine were respectively charged into a reaction flask, 100mL of toluene was then added, the mixture was reacted under N 2 atmosphere at 120℃for 24 hours, extracted with water and CH 2Cl2, concentrated in vacuo, and subjected to column chromatography with a solvent of CH 2Cl2:petroleum ether=1:1 (v/v) to give the intermediate (A2);
Under N 2 atmosphere, 0.5mol of intermediate (A2) and 50mL of m-xylene are filled into a reaction bottle, 0.65mol of N-BuLi is added at-40 ℃ and reacted for 1 hour, and then the reaction is carried out for 1 hour at room temperature; 0.65mol BBr 3 was added and reacted at-40℃for 1 hour, followed by 1 hour at Room Temperature (RT); adding 1.03mol of N, N-diisopropylethylamine at 0 ℃, heating to 120 ℃ and reacting for 12 hours, adding a sodium acetate buffer solution and extracting with CH 2Cl2, and concentrating in vacuum to obtain a main ligand (A3);
1mol of salicylaldehyde, 1mol of N-phenyl-o-phenylenediamine and 1mol of Na 2S2O5 are mixed in 50mL of DMF, react for 3 hours at 150 ℃, water is added after cooling, a filter cake is obtained after filtering, and the filter cake is dried and recrystallized by ethanol to obtain an auxiliary ligand (A4);
2.5mol of main ligand (A3) and 1mol of IrCl 3·H2 O are respectively filled into a reaction bottle, 90mL of ethylene glycol monoethyl ether (EtOCH 2CH2 OH) and 30mL of water are added for reaction for 24 hours at the temperature of 110 ℃ in the atmosphere of N 2, water is added and filtration is carried out to obtain a filter cake, and after drying, further purification is not needed, so as to obtain a dichloro bridged intermediate (A5);
dichloro-bridged intermediate (A5) and auxiliary ligand (A4) were added to the reaction flask, reacted for 24 hours at 60 ℃ in an atmosphere of N 2, concentrated in vacuo, CH 2Cl2: petroleum ether=3:2 (v/v) column chromatography gives iridium (III) complex of formula (Ir-1).
An iridium (III) complex of formula (Ir-1) has the formula: c 65H39B2IrN4O5; molecular mass: 1169.89; elemental analysis: theory of: c,66.73; h,3.36; b,1.85; ir,16.43; n,4.79; o,6.84; actual: c,66.78; h,3.39; b,1.82; ir,16.40; n,4.82; o,6.87; nuclear magnetic resonance hydrogen spectrum ：1H NMR(400MHz,DMSO-d6):δ(ppm)＝8.54(d,2H,-Py),8.53(s,1H,-Ph),7.83(d, 2H,-Ph),7.72(d,4H,-Ph),7.64-7.56(m,3H,-Ph),7.47-7.23(m,15H,-Ph), 7.07-6.92(m,12H,-Ph).
According to the preparation process of the iridium (III) complex with the structural formula (Ir-1), iridium (III) complexes with the structural formulas (Ir-1) - (Ir-8) can be prepared, and iridium (III) complexes with other structural formulas in the invention can also be prepared.
Preparation of a light emitting device:
The first link of preparing the device is to clean ITO glass, which not only can improve the surface roughness and the surface hydrophilicity, but also can increase the surface work function, thereby avoiding carrier traps and being beneficial to hole injection. Firstly, soaking ITO glass in a mixed solution of deionized water and a cleaning agent in the same proportion, and carrying out ultrasonic cleaning on the ITO glass for 30 min; then, sequentially placing the materials in acetone and isopropyl alcohol, and respectively ultrasonically cleaning for 15min; then, drying by a nitrogen gun, and placing in a blast drying oven at 120 ℃ for 2 hours; finally, performing oxygen plasma surface treatment for 5min by a plasma cleaner; and (3) evaporating an organic layer material layer by layer on the ITO substrate under the condition of high vacuum (10 -5 Pa), and controlling the evaporation rate by controlling the magnitude of the loading current so as to further reach the target film thickness, wherein the device is packaged by adopting a glass cover plate.
The structure of the light emitting device may be as shown in fig. 1, the light emitting device including: the second electrode 22, the hole injection layer 321, the hole transport layer 322, the light emitting layer 10, the hole blocking layer 33, the electron transport layer 312, the electron injection layer 311, and the first electrode 21 are stacked, and the first electrode 21 may be a cathode and the second electrode 22 may be an anode. The second electrode 22 is an ITO anode with a transparent circuit, and the thickness of the second electrode can be 130nm; the hole injection layer 321 may be PPBI material and the thickness may be 20nm; the hole transport layer 322 is an NPD material, and may have a thickness of 20nm; the light emitting layer 10 may be doped with iridium (III) complex at a doping concentration of 5wt% to the host of the exciplex, and the thickness of the light emitting layer 10 may be 40nm; the hole blocking layer 33 is a DPB material, and may have a thickness of 50nm; the electron transport layer 312 may be doped with Liq at a doping concentration of 20wt% to the DPB, and may be 20nm thick; the electron injection layer 311 may be a Liq material, and the thickness may be 1nm; the second electrode 22 may be cathode Al, and the thickness may be 80nm; wherein the exciplex bodies are alpha NPD (p-type) and NBPhen (n-type). The structure of the light emitting device can be expressed as: ITO/PPBI/NPD/αNPD NBPhen 5wt% Iridium (III) complex/DPB/DPB 20wt% Liq/Liq/Al.
The structural formula of each layer of material is shown as follows:
the energy levels of the different materials can be as in table 1:
TABLE 1 Material energy levels
The packaged devices were tested for electroluminescent properties, mainly including the peak luminescence spectrum (V on at the onset voltage of lambda EL)、1cd/m2, current efficiency (CE max), maximum power efficiency (PE max), and maximum external quantum efficiency (LT 95 lifetime at EQE max)、15mA/cm2).
Table 2 example device performance
As is clear from table 2, the light-emitting layers of the different devices use different iridium (III) complexes, and the devices having the iridium (III) complexes have a narrow full width at half maximum (FWHM) of light emission, and can obtain red phosphorescence with good color purity, a low starting voltage, a high maximum external quantum efficiency (EQEmax), and a long lifetime of LT 95 at 15mA/cm 2.
Full vacuum deposited device structure
The preparation process of the device comprises the following steps: the first link of preparing the device is to clean ITO glass, which not only improves the surface roughness, thereby improving the surface hydrophilicity, but also increases the surface work function, thereby avoiding carrier traps and being beneficial to hole injection. Firstly, soaking ITO glass in a mixed solution of deionized water and a cleaning agent in the same proportion, and carrying out ultrasonic cleaning for 30min; then, sequentially placing the materials in acetone and isopropyl alcohol, and respectively ultrasonically cleaning for 15min; then, drying by a nitrogen gun, and placing in a blast drying oven at 120 ℃ for 2 hours; finally, the plasma cleaner performs oxygen plasma surface treatment for 5min. And (3) evaporating an organic layer material layer by layer on the ITO substrate under the condition of high vacuum (10 -5 Pa), and controlling the evaporation rate by controlling the magnitude of the loading current so as to further reach the target film thickness, wherein the device is packaged by adopting a glass cover plate.
The device structure prepared can be expressed as: ITO/HATCN (thickness 20 nm)/TAPC (thickness 40 nm nm)/mCP (thickness 5 nm)/CBP 5wt% iridium (III) complex (thickness 30 nm)/TPBi (thickness 40 nm)/LiF (thickness 1 nm)/Al (thickness 100 nm). The structural formula of the materials used can be as follows:
the energy levels of the different materials can be as in table 3:
TABLE 3 Material energy levels
The specific test results for the different devices using different iridium (III) complexes in the light-emitting layers of the different devices are shown in table 4.
Table 4 example device performance
As is clear from Table 4, the light-emitting layers of the various devices use various iridium (III) complexes, and the devices having the iridium (III) complexes have a narrow half-width of light emission, and can obtain red phosphorescence with good color purity, low starting voltage, high maximum external quantum efficiency, and long LT 95 lifetime at 15mA/cm 2.
Solution spin-coatable device structure:
Preparing a device: firstly, ultrasonic waves and acetone are used for cleaning an ITO substrate, and then ethanol is used for cleaning; the substrate was then dried with N 2 and then treated with UV-ozone. Spin-coating a PEDOT PSS layer on an ITO substrate, and annealing for 10min at 120 ℃ in an N 2 atmosphere; and (5) preparing the luminescent layer by adopting a spin coating method, and annealing for 10min at 50 ℃ in an N 2 atmosphere. The electron transport material and the cathode material are prepared by adopting a vacuum evaporation method, and the device is packaged by a glass cover plate.
The structure of the prepared device can be as follows: ITO/PEDOT: PSS (thickness 50 nm)/45% CBP:45% m-MTDATA:10wt% iridium (III) complex (thickness 60 nm)/DPEPO (thickness 10 nm)/TmPyPB (thickness 50 nm)/Liq (thickness 1 nm)/Al (thickness 100 nm).
The energy levels of the different materials can be as in table 5:
TABLE 5 Material energy levels
The specific test results for the different devices using different iridium (III) complexes in the light-emitting layers of the different devices are shown in table 6.
Table 6 example device performance
As is clear from Table 6, the light-emitting layers of the various devices use various iridium (III) complexes, and the devices having the iridium (III) complexes have a narrow half-width of light emission, and can obtain red phosphorescence with good color purity, low starting voltage, high maximum external quantum efficiency, and long LT 95 lifetime at 15mA/cm 2.
The red light emitting device can be prepared, and the structure of the red light emitting device is as follows: ITO/HATCN (thickness 20 nm)/TAPC (thickness 40 nm)/mCP (5 thickness nm)/CBP 5wt% Iridium (III) complex (thickness 30 nm)/TPBi (thickness 40 nm)/5 wt% Ag: m-dPhen/10wt% MoO 3: TAPC/TAPC (thickness 40 nm)/mCP (thickness 5 nm)/CBP 5wt% iridium (III) complex (thickness 30 nm)/TPBi (thickness 40 nm)/LiF (thickness 1 nm)/Al (thickness 100 nm). The red light OLEDs of the tandem structure further include a Charge Generation Layer (CGL) between the first light emitting part and the second light emitting part, and the Charge Generation Layer (CGL) may have a P-N junction structure composed of an N-type charge generation layer and a P-type charge generation layer, the N-type charge generation layer being 5wt% Ag: m-dPhen the P-type charge generation layer was 10wt% moo 3: TAPC.
The structural formula of m-dPhen is as follows:
HOMO＝-6.3eV，LUMO＝-2.9eV。
The specific test results for the different devices using different iridium (III) complexes in the light-emitting layers of the different devices are shown in table 7.
Table 7 example device performance
As is clear from Table 7, the light-emitting layers of the various devices use various iridium (III) complexes, and the devices having the iridium (III) complexes have a narrow half-width of light emission, and can obtain red phosphorescence with good color purity, low starting voltage, high maximum external quantum efficiency, and long LT 95 lifetime at 15mA/cm 2.
Therefore, when different types of light-emitting devices are prepared, the half-width of the light emitted by the device can be narrower by utilizing the phosphorescent material, and the red phosphorescence with good color purity can be obtained, and the light-emitting device has the advantages of low starting voltage, high efficiency and long service life.
An embodiment of the present invention provides a display substrate including the light emitting device described in the above embodiment. The display substrate having the light emitting device described in the above embodiments can have a high color gamut, high efficiency, and long lifetime.
An embodiment of the present invention provides a display device including the display substrate described in the foregoing embodiment. The display device having the display substrate described in the above embodiments can have a high color gamut, high efficiency, and long lifetime.
The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many forms may be made by those having ordinary skill in the art without departing from the spirit of the present invention and the scope of the claims, which are to be protected by the present invention.
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