WO2022143567A1 - Dispositif photoélectrique - Google Patents

Dispositif photoélectrique Download PDF

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WO2022143567A1
WO2022143567A1 PCT/CN2021/141798 CN2021141798W WO2022143567A1 WO 2022143567 A1 WO2022143567 A1 WO 2022143567A1 CN 2021141798 W CN2021141798 W CN 2021141798W WO 2022143567 A1 WO2022143567 A1 WO 2022143567A1
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layer
hole transport
quantum dot
energy level
optoelectronic device
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PCT/CN2021/141798
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Chinese (zh)
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杨一行
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Tcl科技集团股份有限公司
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H10K50/115—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising active inorganic nanostructures, e.g. luminescent quantum dots
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/14—Carrier transporting layers
    • H10K50/16—Electron transporting layers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2101/00—Properties of the organic materials covered by group H10K85/00
    • H10K2101/40—Interrelation of parameters between multiple constituent active layers or sublayers, e.g. HOMO values in adjacent layers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2102/00—Constructional details relating to the organic devices covered by this subclass

Definitions

  • the present application relates to the field of display technology, in particular to an optoelectronic device.
  • QLED Quantum dot light-emitting display technology
  • OLED organic light-emitting display
  • QLED is an active light-emitting technology, so it also has high luminous efficiency, fast response speed, high contrast, Wide viewing angle and other advantages.
  • QLED Due to the excellent material properties of quantum dots in QLED display technology, QLED has performance advantages over OLED in many aspects, such as: the emission of quantum dots is continuously adjustable and the emission width is extremely narrow, which can achieve a wider color gamut and higher Purity display; the inorganic material characteristics of quantum dots make QLED have better device stability; the driving voltage of QLED device is lower than that of OLED, which can achieve higher brightness and reduce energy consumption; at the same time, QLED display technology and printing display production process and The matching technology can realize the high-efficiency mass production preparation of large size, low cost, and rollability. Therefore, QLED is considered to be one of the preferred technologies for next-generation display screens that are thin, portable, flexible, transparent and high-performance in the future.
  • the device structure of QLED is more borrowed from OLED display technology, except that the light-emitting layer material is replaced by organic light-emitting material.
  • other functional layer materials such as charge injection layer or charge transport layer, often use existing materials in OLEDs.
  • the explanation of device physics in QLED devices, the selection and collocation of energy levels of functional layer materials, etc. also follow the existing theoretical system in OLED.
  • the application of the classical device physics conclusions obtained in the research of OLED devices to the QLED device system has indeed significantly improved the performance of QLED devices, especially the efficiency of QLED devices.
  • One of the purposes of the embodiments of the present application is to provide an optoelectronic device, which aims to solve the problem that it is difficult to simultaneously improve the optoelectronic efficiency and lifetime performance of the QLED device in the related art.
  • An optoelectronic device comprising: an anode, a hole transport layer on the anode, a quantum dot light emitting layer on the hole transport layer, an electron transport layer on the quantum dot light emitting layer, and A cathode on the electron transport layer; wherein, the quantum dot light-emitting layer includes a core-shell structure quantum dot material, and the outer shell layer material of the quantum dot material has a valence of the hole transport material in the hole transport layer.
  • the energy level difference at the top of the band is greater than or equal to 0.5 eV; the electron transport layer includes a zinc oxide thin film layer with a surface hydroxyl amount of less than or equal to 0.4.
  • a valence band top energy level difference greater than or equal to 0.5 eV is constructed between the outer shell layer material of the quantum dot material and the hole transport material, that is, EEML-HTL ⁇ 0.5 eV.
  • the hole injection efficiency is reduced by increasing the hole injection barrier, thereby balancing the injection balance of holes and electrons in the light-emitting layer.
  • the electron transport layer uses a zinc oxide film layer with a surface hydroxyl content of less than or equal to 0.4.
  • the electronegativity of the zinc oxide nanomaterial is reduced, thereby reducing the band
  • the negatively charged hydroxyl group inhibits and hinders the electron transport, and the electron transport and injection efficiency are improved through the zinc oxide electron transport film layer with the surface hydroxyl amount less than or equal to 0.4. If the amount of hydroxyl groups on the surface of the zinc oxide electron transport thin film layer is greater than 0.4, the injection efficiency of electrons in the quantum dot light-emitting layer will be significantly reduced.
  • the injection rate of holes and the injection rate of electrons are balanced when the light-emitting device is in a stable working state, which can not only improve the recombination efficiency of electrons and holes, but also improve the luminous efficiency , and can avoid charge accumulation caused by unbalanced carrier injection, and improve the service life of the light-emitting device.
  • FIG. 1 is a schematic structural diagram of the optoelectronic device provided by the first aspect of the embodiment of the present application;
  • FIG. 2 is a schematic diagram of a positive structure of a quantum dot light-emitting diode provided by an embodiment of the present application
  • FIG. 3 is a schematic diagram of an inversion structure of a quantum dot light-emitting diode provided by an embodiment of the present application.
  • At least one means one or more
  • plural items means two or more.
  • At least one item(s) below” or similar expressions thereof refer to any combination of these items, including any combination of single item(s) or plural items(s).
  • at least one (one) of a, b, or c or, “at least one (one) of a, b, and c” can mean: a,b,c,a-b( That is, a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple respectively.
  • ⁇ E HTL-HIL E HOMO,HTL -E HIL
  • ⁇ E EML-HTL E HOMO,EML -E HTL
  • all energy level/work function values are absolute values, and the absolute value of the energy level is large The energy level is deep, and the absolute value of the energy level is small, the energy level is shallow.
  • the amount of hydroxyl groups on the surface of the zinc oxide film is measured by X-ray photoelectron spectroscopy (XPS).
  • XPS X-ray photoelectron spectroscopy
  • the zinc oxide film is detected, and the O1s energy spectrum in the result can be divided into three sub-peaks by peaks. are the O M peak (peak position is between 529ev-531ev) representing the molar concentration of oxygen atoms in the zinc oxide crystal, the O V peak (peak position is between 531ev-532ev) representing the oxygen vacancy molar concentration in the zinc oxide crystal, O H peak representing the molar concentration of hydroxyl ligands on the surface of ZnO crystals (peak positions are between 532ev-534ev).
  • the area ratio between each sub-peak represents the ratio of the molar concentration of different oxygen atoms in the zinc oxide film. Therefore, the amount of hydroxyl groups on the surface of the zinc oxide film is defined as " OH peak area/ OM peak area", that is, zinc oxide.
  • the amount of hydroxyl groups on the surface of the film the molar concentration of hydroxyl ligands on the surface of the zinc oxide film/the molar concentration of oxygen atoms in the zinc oxide crystal.
  • the key of this application is to simultaneously improve the lifetime and photoelectric efficiency of QLED devices.
  • the time of device efficiency test is usually short, so it characterizes the instantaneous state of the QLED device at the beginning of operation; while the device life characterizes the continuous operation of the device and enters into a stable state The ability to maintain device efficiency after state.
  • the injection rate of electrons into the light-emitting layer is usually faster than that of holes. Therefore, in order to balance and improve the recombination efficiency of holes and electrons in the light-emitting layer of a QLED device, a hole injection layer is usually set in the device, and the injection barrier between two adjacent functional layers is minimized to enhance the hole efficiency. injection efficiency, thereby improving carrier injection efficiency and reducing interfacial charge accumulation.
  • this method can only improve the photoelectric efficiency at the initial instant of the QLED device to a certain extent, but cannot improve the device life at the same time, and even reduces the device life.
  • QLED has some special mechanisms different from the OLED device system.
  • the mechanism is closely related to the performance of QLED devices, especially the device lifetime.
  • this application finds through research that: in the initial working state of the QLED device, the injection rate of electrons in the light-emitting layer is faster than that of holes, resulting in the negative charge of the quantum dot material. Factors such as ligand binding and Coulomb blocking effects are maintained.
  • the negatively charged state of the quantum dot material makes it more and more difficult to inject electrons during the continuous operation of the QLED device, resulting in an imbalance between the actual injection of electrons and holes in the light-emitting layer.
  • the negatively charged state of the quantum dot material also tends to be stable, that is, the electrons newly captured and bound by the quantum dots reach a dynamic balance with the electrons consumed by the radiative transition.
  • the injection rate of electrons into the light-emitting layer is much lower than that in the initial state, and the hole injection rate required to achieve the balance of charge injection in the light-emitting layer is actually relatively low.
  • the hole injection efficiency is still improved based on the theoretical system of traditional OLED devices, the use of deep-level hole transport layers can only form an instantaneous balance of charge injection in the initial stage of QLED device operation, and achieve high device efficiency at the initial instant.
  • the QLED device enters a stable working state, excessive hole injection will aggravate the unbalanced state of electrons and holes in the light-emitting layer of the device, and the efficiency of the QLED device cannot be maintained, and thus decreases. And this charge imbalance will continue to increase as the device continues to work, resulting in a corresponding rapid decline in the life of the QLED device.
  • the key to fine-tuning the carrier injection of holes and electrons on both sides of the device is: on the one hand , regulate the hole injection rate to a lower rate, and improve the electron injection efficiency at the same time, so that the hole injection rate and the electron injection rate in the stable working state of the QLED device are balanced, and the recombination efficiency of the QLED device is improved.
  • the hole injection rate required for QLED devices in the actual stable operating state is lower than traditionally expected, carrier accumulation is prone to occur, causing irreversible damage to the device. Therefore, the influence of carrier accumulation on the device life should be avoided as much as possible, and the device life should be improved.
  • a first aspect of an embodiment of the present application provides an optoelectronic device, comprising: an anode, a hole transport layer on the anode, a quantum dot light-emitting layer on the hole transport layer, and a quantum dot light-emitting layer on the The electron transport layer on the electron transport layer, and the cathode on the electron transport layer; wherein, the quantum dot light-emitting layer includes a core-shell structure quantum dot material, and the outer shell layer material of the quantum dot material is hollow with the hole transport layer
  • the top energy level difference of the valence band of the hole transport material is greater than or equal to 0.5 eV; the electron transport layer includes a zinc oxide thin film layer with a surface hydroxyl amount of less than or equal to 0.4.
  • a valence band top energy level difference greater than or equal to 0.5 eV is constructed between the outer shell layer material of the quantum dot material and the hole transport material, that is, E EML-HTL ⁇ 0.5 eV.
  • the hole injection efficiency is reduced by increasing the hole injection barrier, thereby balancing the injection balance of holes and electrons in the light-emitting layer.
  • the electron transport layer uses a zinc oxide film layer with a surface hydroxyl content of less than or equal to 0.4.
  • the electronegativity of the zinc oxide nanomaterial is reduced, thereby reducing the band
  • the negatively charged hydroxyl group inhibits and hinders the electron transport, and the electron transport and injection efficiency are improved through the zinc oxide electron transport film layer with the surface hydroxyl amount less than or equal to 0.4. If the amount of hydroxyl groups on the surface of the zinc oxide electron transport thin film layer is greater than 0.4, the injection efficiency of electrons in the quantum dot light-emitting layer will be significantly reduced.
  • the injection rate of holes and the injection rate of electrons are balanced when the light-emitting device is in a stable working state, which can not only improve the recombination efficiency of electrons and holes, but also improve the luminous efficiency , and can avoid charge accumulation caused by unbalanced carrier injection, and improve the service life of the light-emitting device.
  • this application finds that at least an energy level barrier of ⁇ E EML-HTL ⁇ 0.5 eV is required to achieve high hole injection efficiency. Remarkably reduced to balance the injection efficiency of electrons and holes in the light-emitting layer.
  • the hole injection barrier of ⁇ E EML-HTL ⁇ 0.5eV in the present application will not prevent holes from being injected, because the energy level of the outer shell of the quantum dots will be band-bended in the energized working state, and carriers can pass through. The tunneling effect realizes the injection; thus, although this increase in the energy level barrier will cause a decrease in the carrier injection rate, it will not completely hinder the final injection of carriers.
  • the core material determines the luminescence performance
  • the shell material protects and facilitates carrier injection
  • electrons and holes are injected into the core through the shell layer to emit light.
  • the band gap of the inner core is narrower than that of the outer shell, so the energy level difference between the valence band of the hole transport material and the inner core of the quantum dot is smaller than the energy level difference of the valence band of the hole transport material and the outer shell of the quantum dot. Therefore, the ⁇ E EML-HTL is greater than or equal to 0.5 eV, which can simultaneously ensure the effective injection of hole carriers into the inner core of the quantum dot material.
  • the valence band top energy level difference between the outer shell layer material of the quantum dot material and the hole transport material in the hole transport layer is 0.5-1.7 eV, that is, the ⁇ E EML-HTL is 0.5 eV-1.7 eV, and the quantum dot material is 0.5-1.7 eV.
  • the energy level barrier in this range constructed between the outer shell material and the hole transport material can be applied to device systems constructed of different hole transport materials and quantum dot materials to optimize the injection of electrons and holes in different device systems. balance.
  • ⁇ E EML-HTL different top valence band energy level differences ⁇ E EML-HTL can be set according to the specific material properties, and the carrier injection rate of holes and electrons on both sides of the light-emitting layer can be finely adjusted to balance the injection of holes and electrons.
  • the valence band top energy level difference between the shell layer material of the quantum dot material and the hole transport material is 0.5eV ⁇ 0.7eV
  • the applicable hole transport materials are TFB, P12, P15
  • the quantum dot shell material For ZnSe, CdS such as: TFB-ZnSe, P12/P15-CdS and other device systems.
  • the valence band top energy level difference between the outer shell material of the quantum dot material and the hole transport material is 0.7eV ⁇ 1.0eV
  • the applicable hole transport material is TFB, P09
  • the quantum dot shell material is ZnSe , CdS, such as: P09-ZnSe, TFB-CdS and other device systems.
  • the valence band top energy level difference between the outer shell layer material of the quantum dot material and the hole transport material is 1.0eV ⁇ 1.4eV
  • the applicable hole transport materials are TFB, P09, P13, P14
  • the shell materials are CdS, ZnSe, ZnS, such as: TFB-ZnS, P09-CdS, P13/P14-ZnSe and other device systems.
  • the valence band top energy level difference between the outer shell layer material of the quantum dot material and the hole transport material is greater than 1.4eV-1.7eV, and the device system of P09-ZnS and P13/P14-ZnS is applicable.
  • the amount of hydroxyl groups on the surface of the zinc oxide thin film layer is less than or equal to 0.25. In other embodiments, the amount of hydroxyl groups on the surface of the zinc oxide thin film layer is less than or equal to 0.15. Due to the characteristics of zinc oxide nanomaterials themselves, a large number of ionized hydroxyl groups are adsorbed on their surfaces, and these hydroxyl groups are negatively charged, and a large number of them are adsorbed on the surface of zinc oxide nanoparticles, so that the surface of zinc oxide nanoparticles is also negatively charged. The negatively charged hydroxyl groups adsorbed on the surface of zinc oxide will inhibit and hinder the transport of electrons in the zinc oxide electron transport film layer.
  • the amount of hydroxyl groups on the surface of the zinc oxide film will directly affect the electrons in the light-emitting device. injection situation.
  • the amount of surface hydroxyl groups is large, the transmission of electrons in the light-emitting device will be significantly inhibited, and the electrons injected into the light-emitting layer of the quantum dots will be significantly reduced; when the amount of surface hydroxyl groups is small, the transmission of electrons in the light-emitting device will be obviously smooth.
  • the electrons injected into the quantum dot light-emitting layer will increase significantly.
  • the above-mentioned embodiments of the present application control the amount of hydroxyl groups on the surface of the zinc oxide electron transport thin film layer, reduce the inhibition and hindering effect of negatively charged hydroxyl groups on electron transport, ensure the injection efficiency of electrons in the light-emitting layer of the quantum dots, and improve the electrons and holes.
  • the recombination efficiency is improved, the luminous efficiency of the device is improved, the charge accumulation caused by the unbalanced carrier injection is avoided, and the service life of the light-emitting device is improved.
  • the zinc oxide thin film layer is doped with: Mg 2+ , Mn 2+ , Al 3+ , Y 3+ , La 3+ , Li + , Gd 3+ , Zr 4+ , Ce 4 + at least one metal ion.
  • zinc oxide doped with the above-mentioned metal ions is selected.
  • Mg 2+ , Mn 2+ ions and zinc ions have the same valence state but their oxides have different conduction band energy levels.
  • the conduction band energy level of the electron transport layer of zinc oxide can be adjusted, Further, the energy level matching between the quantum dot light-emitting layer and the electron transport layer in the light-emitting device is optimized, thereby improving the electron injection efficiency.
  • Al 3+ , Y 3+ , La 3+ , Li + , Gd 3+ , Zr 4+ , Ce 4+ plasma and zinc ions have different valence states.
  • the oxygen vacancies are tuned to promote electron mobility efficiency, which in turn optimizes the carrier injection balance of the light-emitting device.
  • the doping molar percentage of Mg 2+ is 0.1%-35%; and/or the doping molar percentage of Mn 2+ is 0.1%-30% %; and/or, the doping molar percentage of Al 3+ is 0.1%-15%; and/or, the doping molar percentage of Y 3+ is 0.1%-10%; and/or, La 3
  • the doping molar percentage of + is 0.1%-7%; and/or the doping molar percentage of Li + is 0.1%-45%; and/or the doping molar percentage of Gd 3+ is 0.01%-8%; and/or the doping mole percentage of Zr 4+ is 0.1%-45%; and/or the doping mole percentage of Ce 4+ is 0.1%-10%.
  • the ionic radius of doped metal ions in zinc oxide nanomaterials is different from that of zinc ions, and the crystal structure of doped metal ion oxides is different from that of ZnO, such as: MgO and MnO are NaCl-type cubic crystal system, ZrO 2 is a monoclinic crystal system, etc., while ZnO is a wurtzite-type hexagonal crystal system, which limits the doping amount of metal ions in ZnO nanomaterials.
  • the doping amount of metal ions in the ZnO nanomaterial exceeds the doping limit, the doped metal ions will precipitate from the surface of the ZnO material in the form of a second phase, which is detrimental to the performance of the ZnO electron transport film layer.
  • the embodiments of the present application are based on Mg 2+ , Mn 2+ , Al 3+ , Y 3+ , La 3+ , Li + , Gd 3+ , Zr 4+ , Ce 4+ and other metals doped in the zinc oxide electron transport film.
  • the radius of the ion and the crystal structure of its oxide determine the appropriate molar percentage of doping of each metal ion in the zinc oxide film. Adjusting the conduction band energy level and oxygen vacancies of ZnO nanomaterials can effectively improve the transfer efficiency of electrons and promote the carrier conformity balance in light-emitting devices.
  • the electron transport layer is a laminated composite structure, and in addition to the zinc oxide thin film layer with a surface hydroxyl amount of less than or equal to 0.4, it also includes an electron transport layer of an organic transport material.
  • Organic transport materials can achieve energy level regulation in a wide range. Through the co-coordination of metal oxo compound transport materials and organic transport materials in the electron transport layer, the electron transport layer has both high electron mobility and energy level matching. flexibility. Effective regulation of the energy level and electron mobility of the electron transport layer is achieved, so as to achieve a sufficient match with hole injection.
  • the electron transport layer in the embodiments of the present application can be prepared into a thin film in a light-emitting device by vacuum evaporation or solution method; wherein the solution method includes inkjet printing, spin coating, jet printing, slot coating or screen printing.
  • the electron mobility of the organic transport material is not less than 10 ⁇ 4 cm 2 /Vs.
  • the organic transport material is selected from the group consisting of 8-quinolinolato-lithium, aluminum octaquinolate, fullerene derivatives, 3,5-bis(4-tert-butylphenyl)-4-phenyl -At least one of 4H-1,2,4-triazole and 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene.
  • These organic transport materials can realize energy level regulation in a wide range, which is more conducive to regulating the energy levels of each functional layer of the device and improving the stability and photoelectric conversion efficiency of the device.
  • the electron transport layer further includes a metal oxo compound transport layer, wherein the metal oxo compound is selected from at least one of titanium oxide, zinc sulfide, and cadmium sulfide. These metal oxo compound transport materials all have high electron transfer efficiency.
  • the particle size of the metal oxide transport material is less than or equal to 10 nm.
  • the metal oxide transport material with small particle size is more conducive to deposition to obtain electrons with a dense film layer and a uniform thickness.
  • the thin film of the transmission layer improves the bonding tightness with the adjacent functional layer, reduces the interface resistance, and is more conducive to improving the performance of the device.
  • the metal oxide compound transport material with small particle size has a wider band gap, which reduces the quenching of the exciton emission of the quantum dot material and improves the device efficiency.
  • the electron mobility of the metal oxo compound transport material is 10 -2 to 10 -3 cm 2 /Vs, and the electron transport material with high mobility can reduce the accumulation of charges in the interface layer, improve electron injection, compound efficiency.
  • the QLED device of the embodiment of the present application needs to regulate the hole injection rate to a lower rate in a certain way. Therefore, in some specific embodiments, the hole injection layer may not be provided in the optoelectronic device provided in the first aspect of the embodiments of the present application to enhance the hole injection efficiency.
  • the setting of the hole injection layer in the QLED device can not only improve the hole injection efficiency, but also is the key to regulating the stable and balanced injection of holes, and is also one of the key factors affecting the performance and life of the device. Therefore, in the embodiments of the present application, the hole injection efficiency in the device can also be controlled by arranging a hole injection layer in the device, and the influence of charge accumulation on the life of the device can be avoided. specifically:
  • the voltage rise of the QLED device caused at this time is significantly different from the voltage rise caused by the charge accumulation at the EML interface as follows:
  • the interface between the HIL and the HTL generates an electric field due to the charge accumulation, and the irreversible damage caused by the charge accumulation will follow the device. What happens all the time with continuous energization will continue to deteriorate; while the charge accumulation at the EML interface is reversible and will reach a certain degree of saturation. Therefore, the interfacial charge accumulation between HIL and HTL has a greater impact on the performance of the device, such as lifetime.
  • an optoelectronic device is provided on the basis of the embodiments of the first aspect.
  • the optoelectronic device includes a hole transport layer and a first hole injection layer.
  • the absolute value of the work function difference with the first hole injection material in the first hole injection layer is less than or equal to 0.2 eV.
  • the energy level barrier of hole injection between HTL and HIL can be significantly reduced, and the injection efficiency of holes from the anode can be improved, It is conducive to the effective injection of holes from HIL to HTL, eliminating potential barriers and interface charges, reducing the overall resistance of the device, thereby avoiding irreversible damage caused by charge accumulation at the interface between HIL and HTL, reducing device driving voltage and improving device life. .
  • the absolute value of the difference between the valence band top energy level of the hole transport layer material and the work function of the first hole injection material is 0 eV.
  • is 0, which is more conducive to the effective injection of holes from HIL to HTL, eliminating potential barriers and interface charges, reducing the overall resistance of the device, thereby reducing the driving voltage of the device and improving the life of the device.
  • the absolute value of the work function of the first hole injection material is 5.3 eV ⁇ 5.6 eV
  • the absolute value of the valence band energy level of the hole injection material with the work function size is compared with that of the existing hole transport material. Close to (about 5.4eV), it is beneficial to control
  • HIL and HTL materials with suitable energy levels so that
  • the mobility of the hole transport material is higher than 1 ⁇ 10 ⁇ 4 cm 2 /Vs.
  • hole transport materials with a mobility higher than 1 ⁇ 10 -4 cm 2 /Vs are used to ensure the transport and migration effect of holes, prevent charge accumulation, eliminate interface charges, and better reduce the device driving voltage and improve the device. life.
  • a third aspect of the embodiments of the present application provides an optoelectronic device based on the embodiments of the first aspect, comprising a hole transport layer and a second hole injection layer, wherein the hole transport layer has a valence band top of a material of the hole transport layer.
  • the difference between the energy level and the work function of the second hole injection material in the second hole injection layer is less than -0.2 eV.
  • the anode direction is increased.
  • the hole injection barrier of the HIL reduces the overall rate of hole injection in the QLED device and effectively controls the number of holes entering the QLED device. On the one hand, it effectively reduces the rate of hole injection into the light-emitting layer, balances the hole-electron injection rate in the light-emitting layer, and improves the carrier recombination efficiency; on the other hand, it can avoid excessive hole injection in HTL and HIL.
  • Charge accumulation is formed at the interface to prevent irreversible damage to the life of the device caused by the charge accumulation at the interface.
  • a hole blocking barrier from HTL to HIL is formed, which prevents holes from diffusing to the HIL layer, improves the utilization rate of holes, and ensures the effective "survival" of holes before being injected into the light-emitting layer.
  • the holes injected in the device are fully and effectively utilized, the luminous efficiency of the device is guaranteed, and the device efficiency and service life are improved at the same time.
  • the quantum dot material of the core-shell structure contained in the quantum dot light-emitting layer of the optoelectronic device has a valence band top energy level difference between the outer shell layer material and the hole transport material greater than 0 eV, that is, ⁇ E EML-HTL >0,
  • the hole injection barrier existing in the light-emitting layer and the barrier between HTL and HIL make the transport layer form a hole carrier trap, effectively "storing" the accumulated holes without diffusing to the outside of the HTL layer.
  • the valence band top energy level difference between the outer shell layer material of the quantum dot material and the hole transport material is greater than or equal to 0.5eV ⁇ 1.7eV, that is, the ⁇ E EML-HTL is 0.5eV ⁇ 1.7eV, forming a better empty space.
  • Hole carrier trap in practical application, the hole carrier hydrazine is used to control the injection balance of holes and electrons in the light-emitting layer of the device more precisely, and improve the carrier recombination efficiency.
  • the difference between the valence band top energy level of the hole transport layer material and the work function of the second hole injection material is -0.9eV ⁇ -0.2eV, and the difference between ⁇ E HTL-HIL is -0.9eV ⁇ - 0.2eV, in this range, the injection and transport of holes have a better balance effect. If it is lower than -0.9eV, the hole injection resistance is too large, which will lead to too little hole injection, which is not conducive to the balanced injection and effective recombination of holes and electrons in the light-emitting layer; if the potential barrier is greater than -0.2eV, the hole injection It is easy to form accumulation at the interface, and the utilization rate is not high.
  • the absolute value of the work function of the second hole injection material is 5.4 eV ⁇ 5.8 eV.
  • the absolute value of the work function of the second hole injection material in the embodiment of the present application is 5.4 eV to 5.8 eV, which is favorable for forming a hole blocking barrier with an energy range of less than -0.2 eV with the hole transport material.
  • the absolute value of the valence band of the conventional hole transport material is about 5.3-5.4 eV
  • the second hole injection material with the absolute value of the work function greater than or equal to 5.4 eV can form a negative energy less than -0.2 eV with the conventional hole transport material level difference, thereby forming a hole blocking barrier, optimizing the hole injection rate, and improving the hole utilization rate.
  • the mobility of the hole transport material is higher than 1 ⁇ 10 -4 cm 2 /Vs
  • the embodiment of the present application adopts a hole transport material with a mobility higher than 1 ⁇ 10 -4 cm 2 /Vs to ensure that The transport and migration effect of holes prevents charge accumulation, eliminates interface charges, and better reduces device driving voltage and improves device life.
  • the hole injection material is selected from a metal oxide material. That is, in some embodiments, when the optoelectronic device includes a first hole injection layer, the first hole injection material in the first hole injection layer is selected from metal oxide materials. In other specific embodiments, when the optoelectronic device includes a second hole injection layer, the second hole injection material in the second hole injection layer is selected from metal oxide materials.
  • the metal oxide material used as the hole injection material has better stability and is not acidic, which not only meets the requirements for hole injection in the above embodiments, but also does not affect adjacent holes.
  • the functional layer has a negative impact. The decay of the life of the device caused by the thermal effect or the electrical effect damage of the organic hole injection material during the working process of the device is avoided, and the damage to the adjacent functional layer due to the acidity of the organic hole injection material is avoided.
  • the metal oxide material includes at least one metal nanomaterial selected from tungsten oxide, molybdenum oxide, vanadium oxide, nickel oxide, and copper oxide. These metal nanomaterials not only have better stability, but also have no acidity. , and in the actual application process, the size of the work function can be adjusted to realize the construction of energy level barriers of different sizes with the hole transport layer, which is beneficial to control hole injection and transport, improve the carrier recombination efficiency, and avoid charge accumulation. impact on device life.
  • the particle size of the metal oxide material is 2 to 10 nm, and the metal oxide material with a small particle size is more conducive to depositing a thin film with a dense film layer and a uniform thickness, which improves the bonding with the adjacent functional layer. It can reduce the interface resistance, which is more conducive to improving the device performance.
  • the hole injection material can also be poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid (PEDOT:PSS), HIL2, HIL1-1, HIL1-2, copper phthalocyanine (CuPc), 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinone-dimethane (F4-TCNQ), 2,3,6,7,10,11-hexa Organic hole injection materials such as cyano-1,4,5,8,9,12-hexaazatriphenylene (HATCN).
  • PEDOT:PSS poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid
  • HIL2 HIL1-1, HIL1-2
  • CuPc copper phthalocyanine
  • F4-TCNQ 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinone-dimethane
  • HTCN 2,3,6,7
  • PEDOT:PSS contains the structural formula: The organic molecule of , its work function is -5.1eV; HIL2 contains the structural formula: The organic molecule of , its work function is -5.6eV; HIL1-1 and HIL1-2 both contain the structural formula: The work function of HIL1-1 is -5.4 eV and the work function of HIL1-2 is -5.3 eV.
  • the thickness of the first hole injection layer is 10-150 nm. In other embodiments, the thickness of the second hole injection layer is 10-150 nm.
  • the thickness of the hole injection layer of the present application can be flexibly adjusted according to actual application requirements, and at the same time, the hole injection rate can be better adjusted by adjusting the thickness of the hole injection layer.
  • the hole transport material is selected from at least one of TFB, poly-TPD, P11, P09, P13, P15, P12. In other embodiments, the hole transport material has a mobility higher than 1 ⁇ 10 ⁇ 4 cm 2 /Vs.
  • the hole transport material provided by the above embodiments of the present application can not only build a hole injection barrier with an energy level difference greater than or equal to 0.5 eV with the outer shell layer material of the quantum dot material, but also effectively ensure the migration rate of holes and avoid the slow migration rate. Charge accumulation increases the service life of the device.
  • the embodiments of the present application achieve the purpose of reducing the hole injection rate in the QLED device, regulating the injection and recombination efficiency of carriers, and avoiding HIL and HTL at the same time. Interfacial charge accumulation causes irreversible damage to device lifetime performance.
  • a fourth aspect of the present application provides an optoelectronic device, the hole transport layer of the optoelectronic device comprises at least two hole transport materials, wherein the valence band top energy level of at least one hole transport material The absolute value of is less than or equal to 5.3 eV, and the absolute value of the top energy level of the valence band of at least one hole transport material is greater than 5.3 eV.
  • the hole transport layer of the optoelectronic device provided by the fourth aspect of the present application is a hybrid material, wherein the top energy level of the valence band of at least one hole transport material is less than or equal to 5.3 eV, while the shell energy level of conventional quantum dot light-emitting materials is often relatively Deep (6.0 eV or deeper), therefore, an energy level difference of 0.5 eV or more is formed between the hole transport material of the shallow energy level and the quantum dot shell material.
  • the hole transport layer through the combination of shallow-level materials and deep-level materials, the fine control of the hole injection barrier between the hole transport material and the quantum dot shell layer can be achieved.
  • the hole transport material with deep energy levels modulates the hole mobility in the HTL layer.
  • the hole transport layer further includes a hole transport material whose absolute value of the top energy level of the valence band is greater than 5.3 eV and less than 5.8 eV. In some embodiments, the hole transport layer further includes a hole transport material whose absolute value of the top energy level of the valence band is greater than or equal to 5.8 eV. In other embodiments, the hole transport layer simultaneously includes a hole transport material with an absolute value of the top energy level of the valence band greater than 5.3 eV and less than 5.8 eV and holes with an absolute value of the top energy level of the valence band greater than or equal to 5.8 eV transfer material.
  • the hole injection barrier can be flexibly adjusted according to practical application requirements, device systems and other factors, so that the injection energy level barrier of holes to the light-emitting material is greater than or equal to 0.5eV, reducing the injection efficiency of holes, thereby balancing the injection balance of holes and electrons in the light-emitting layer, and the application is flexible and convenient.
  • the electron transport layer of the optoelectronic device is selected to include: an organic electron transport material layer, ZnO nanoparticles, etc. At least one of a metal oxide nanoparticle layer, a sputter deposited metal oxide layer.
  • the hole transport layer when the hole transport layer includes at least one hole transport material with a valence band top energy level of less than or equal to 5.3 eV and a valence band top energy level greater than 5.3 eV and less than 5.8 eV, the hole transport The layer has a relatively moderate top energy level of the valence band and hole mobility, so it can be well matched with conventional metal oxides such as ZnO or organic electron transport materials, which is beneficial to the regulation of the charge balance between holes and electrons.
  • the electron transport layer of the optoelectronic device is selected to include: metal oxide nanoparticles, and the surface groups are selected to connect more Fewer metal oxide nanoparticles.
  • the hole transport layer includes a hole transport material whose valence band top energy level is greater than 5.8 eV, the energy level and mobility are both the same as the valence band top energy level of the aforementioned hole transport material.
  • the hole transport layer materials with a shallow valence band top energy level of less than or equal to 5.3eV have great differences, and continuous regulation in a large window range can be achieved through different mixing ratios, which is suitable for devices from the initial state to continuous operation to QLED device systems with more variable electron injection and transport changes during steady state, such as metal oxide nanoparticles with fewer surface groups attached.
  • the mass percentage of the hole transport material whose absolute value of the top energy level of the valence band is less than or equal to 5.3 eV is 30-90%; According to the content, it can form a hole injection barrier greater than or equal to 0.5eV with the outer shell layer of the luminescent material. In practical applications, the mixing ratio of materials of each energy level can be flexibly adjusted according to the depth of the material energy level.
  • the mobility of at least one hole transport material is higher than 1 ⁇ 10 -3 cm 2 /Vs, and the high mobility of the hole transport material in the embodiments of the present application ensures that holes It can improve the transport and migration performance and avoid the accumulation of holes at the interface, which will affect the device performance.
  • the top energy level of the valence band of the hole transport layer material with high hole mobility is relatively shallow, which also ensures the formation of a suitable energy range with the quantum dot shell material.
  • the mobility of the at least one hole transport material in the hole transport layer is higher than 1 ⁇ 10 ⁇ 2 cm 2 /Vs. In other specific embodiments, in the hole transport layer, the mobility of each hole transport material is higher than 1 ⁇ 10 -3 cm 2 /Vs.
  • the above-mentioned embodiments of the present application optimize the mobility of hole transport materials, ensure the hole transport efficiency, avoid charge accumulation affecting device performance, and ensure the combination of deep and shallow hole transport materials in the hole transport layer.
  • the injection barrier of the hole ensures the formation of an energy level barrier with ⁇ E EML-HTL greater than or equal to 0.5eV, and optimizes the injection balance and recombination efficiency of carriers in the QLED device.
  • a fifth aspect of the present application provides an optoelectronic device, the hole transport layer of the optoelectronic device includes at least two kinds of hole transport materials, and the absolute value of the top energy level of the valence band of the hole transport materials is less than is equal to 5.3eV.
  • the hole transport layer of the optoelectronic device provided by the fifth aspect of the present application is a mixed material, and the top energy level of the valence band of the hole transport material is all less than or equal to 5.3 eV, and the quantum dot light-emitting material with a deeper shell energy level can form a quantum dot light-emitting material greater than or equal to 0.5eV energy level difference.
  • the device ⁇ E EML-HTL ⁇ 0.5 eV. Therefore, after the QLED device enters a stable working state, the charge injection balance and the device efficiency are maintained, and the device life is optimized.
  • the hole mobility of the mixed hole transport layer can also be finely regulated by different mixing ratios by using the different hole mobilities of the hole transport layer materials that are also all of the hole transport layer materials with shallow valence band top energy levels.
  • the mass percentage of each hole transport material is 5-95%.
  • the hole mobility and injection barrier of the hole transport layer can be better controlled.
  • the mobility of at least one hole transport material is higher than 1 ⁇ 10 -3 cm 2 /Vs, and the hole transport layer material with high hole mobility has a top energy level in the valence band. relatively shallow.
  • the mobility of the hole transport material is limited, and the high mobility ensures the transport and mobility of holes, and at the same time ensures the formation of a more suitable injection barrier, so as to avoid the accumulation of holes at the interface and affect the device performance.
  • the mobility of at least one hole transport material in the hole transport layer is higher than 1 ⁇ 10 ⁇ 2 cm 2 /Vs.
  • the mobility of each hole transport material in the hole transport layer is higher than 1 ⁇ 10 ⁇ 3 cm 2 /Vs.
  • the selection of the electron transport layer of the optoelectronic device includes: surface-passivated metal oxide nanoparticles, and the selected surface is sufficient Modification of passivated metal oxide nanoparticles.
  • the top energy level of the valence band of the hole transport material in the hole transport layer is all less than or equal to 5.3 eV, it is necessary to correspond to the material with small changes in electron injection and transport. At this time, it is suitable for the device from the initial state to continuous operation to a stable state. QLED device systems with less variation in electron injection and transport changes during the process, such as metal oxide nanoparticles with adequate surface modification and passivation.
  • the hole transport material is at least one selected from the group consisting of polymers containing aniline groups and copolymers containing fluorene groups and aniline groups, and these hole transport materials have holes It has the advantages of high transmission efficiency, good stability and easy access.
  • hole transport materials with suitable energy level and mobility can be selected according to the actual application requirements, specifically:
  • a hole transport material with an absolute value of valence band top energy level less than or equal to 5.3 eV can be selected: At least one of P09 and P13. Among them, the structural formula of P13 is: The structural formula of P09 is:
  • the transmission material includes: at least one of TFB, poly-TPD, and P11.
  • the structural formula of P11 is:
  • the structural formula of poly-TPD is:
  • the structural formula of TFB is:
  • the hole transport material with an absolute value of valence band top energy level greater than or equal to 5.8 eV includes: At least one of P15 and P12. Among them, the structural formula of P12 is: The structural formula of P15 is:
  • the mobility of the hole transport material is higher than 1 ⁇ 10 -4 cm 2 /Vs, and the high mobility ensures the transport and mobility of holes and avoids the effect of charge accumulation on the device lifetime.
  • the quantum dot material of the core-shell structure further includes an inner core, and an intermediate shell layer located between the inner core and the outer shell layer; wherein, the top energy level of the valence band of the core material is shallower than the valence band of the outer shell layer material Top energy level; the top energy level of the valence band of the intermediate shell material is between the top energy level of the valence band of the core material and the top energy level of the valence band of the outer shell material.
  • the core material determines the luminescence performance
  • the shell material plays the role of protection and facilitates the injection of carriers
  • the intermediate shell layer with the valence band between the core and the shell layer plays an intermediate role.
  • the transition effect is more conducive to carrier injection.
  • the intermediate shell layer can form a stepped energy level transition from the inner core to the outer shell layer, which helps to achieve effective carrier injection, effective confinement and reduction of lattice. interface flickering.
  • the outer shell layer of the quantum dot material includes: an alloy material formed by at least one or at least two of CdS, ZnSe, ZnTe, ZnS, ZnSeS, CdZnS, and PbS.
  • These shell layer materials not only protect and facilitate the injection of carriers into the quantum dot core for light emission, but also form an energy level barrier with ⁇ E EML-HTL greater than or equal to 0.5eV with the HTL layer material.
  • the injection efficiency of holes is improved, so as to balance the injection balance of holes and electrons in the light-emitting layer, improve the luminous efficiency of the device, and avoid the influence of charge accumulation on the life of the device.
  • the inner core of the quantum dot material includes: at least one of CdSe, CdZnSe, CdZnS, CdSeS, CdZnSeS, InP, InGaP, GaN, GaP, ZnSe, ZnTe, ZnTeSe.
  • the luminescent properties of quantum dot materials are related to the core materials. These materials ensure that QLED devices can emit light in the visible light range of 400-700 nm, which not only meets the range required for the application of optoelectronic display devices, but also the beneficial effects achieved by the energy level relationship of these materials can be achieved. better reflect.
  • the intermediate shell material is selected from at least one of CdZnSe, ZnSe, CdZnS, CdZnSeS, CdS, CdSeS.
  • the composition of the intermediate shell layer in the embodiment of the present application, it is preferable to form a continuous and natural transition of the composition from the inner core to the outer layer, which helps to achieve the least lattice mismatch between the inner core, the intermediate shell layer and the outer shell layer. And the least lattice defects, so as to achieve the optimal luminescence performance of the core-shell quantum dot material itself.
  • the emission peak wavelength range of the quantum dot material is 400-700 nm. On the one hand, this wavelength range is required for the application of optoelectronic display devices; The beneficial effect can be better reflected.
  • the thickness of the outer shell layer of the quantum dot material is 0.2-6.0 nm, which covers the thickness of the conventional outer shell and can be widely used in QLED devices of different systems. If the thickness of the outer shell layer is too large, the rate at which carriers are injected into the light-emitting quantum dots through the tunneling effect will decrease; and if the thickness of the outer shell layer is too small, the outer shell material cannot sufficiently protect and passivate the core material. , which affects the luminescence and stability properties of quantum dot materials.
  • the core material determines the luminescence properties of the quantum dot material
  • the shell material plays a protective role and is conducive to carrier injection.
  • the thickness of the shell layer and the top energy level of the valence band of the hole transport material can be adjusted so that the difference in the top energy level of the valence band between the shell layer material of the quantum dot material and the hole transport material is greater than or equal to 0.5 eV, that is, to construct the expected injection barrier, E EML-HTL ⁇ 0.5 eV, optimize the balance of electron and hole injection efficiency in the light-emitting layer, and improve the device efficiency and service life.
  • the device is not limited by the device structure, and may be a device with a positive structure or a device with an inversion structure.
  • the positive structure optoelectronic device includes a stacked structure of oppositely disposed anode and cathode, a light-emitting layer disposed between the anode and the cathode, and the anode disposed on the substrate.
  • a hole functional layer such as a hole injection layer and a hole transport layer can also be set between the anode and the light-emitting layer; and an electron functional layer such as an electron transport layer and an electron injection layer can also be set between the cathode and the light-emitting layer, as shown in Figure 2 shown.
  • the optoelectronic device includes a substrate, an anode disposed on the surface of the substrate, a hole transport layer disposed on the surface of the anode, a light emitting layer disposed on the surface of the hole transport layer, An electron transport layer on the surface of the layer and a cathode disposed on the surface of the electron transport layer.
  • the inversion structure optoelectronic device comprises a stacked structure of oppositely disposed anode and cathode, a light-emitting layer disposed between the anode and the cathode, and the cathode disposed on the substrate.
  • a hole functional layer such as a hole injection layer and a hole transport layer can also be set between the anode and the light-emitting layer; and an electron functional layer such as an electron transport layer and an electron injection layer can also be set between the cathode and the light-emitting layer, as shown in Figure 3 shown.
  • the optoelectronic device includes a substrate, a cathode disposed on the surface of the substrate, an electron transport layer disposed on the surface of the cathode, a light emitting layer disposed on the surface of the electron transport layer,
  • the hole transport layer is an anode disposed on the surface of the hole transport layer.
  • the choice of the substrate is not limited, and a rigid substrate or a flexible substrate may be used.
  • the rigid substrate includes, but is not limited to, one or more of glass and metal foil.
  • the flexible substrate includes, but is not limited to, polyethylene terephthalate (PET), polyethylene terephthalate (PEN), polyetheretherketone (PEEK), polystyrene (PS), polyethersulfone (PES), polycarbonate (PC), polyarylate (PAT), polyarylate (PAR), polyimide (PI), polyvinyl chloride (PV), poly One or more of ethylene (PE), polyvinylpyrrolidone (PVP), and textile fibers.
  • PET polyethylene terephthalate
  • PEN polyethylene terephthalate
  • PEEK polyetheretherketone
  • PS polystyrene
  • PS polyethersulfone
  • PC polycarbonate
  • PAT polyarylate
  • PAR polyarylate
  • PI polyimide
  • PV polyviny
  • the choice of anode material is not limited and can be selected from doped metal oxides, including but not limited to indium doped tin oxide (ITO), fluorine doped tin oxide (FTO), antimony doped tin oxide (ATO), Aluminum-Doped Zinc Oxide (AZO), Gallium-Doped Zinc Oxide (GZO), Indium-Doped Zinc Oxide (IZO), Magnesium-Doped Zinc Oxide (MZO), Aluminum-Doped Magnesium Oxide (AMO) one or more.
  • doped metal oxides including but not limited to indium doped tin oxide (ITO), fluorine doped tin oxide (FTO), antimony doped tin oxide (ATO), Aluminum-Doped Zinc Oxide (AZO), Gallium-Doped Zinc Oxide (GZO), Indium-Doped Zinc Oxide (IZO), Magnesium-Doped Zinc Oxide (MZO), Aluminum-Doped Magnesium Oxide (AMO)
  • the cathode material may be one or more of various conductive carbon materials, conductive metal oxide materials, and metallic materials.
  • conductive carbon materials include, but are not limited to, doped or undoped carbon nanotubes, doped or undoped graphene, doped or undoped graphene oxide, C60, graphite, carbon fiber, many Empty carbon, or a mixture thereof.
  • the conductive metal oxide material includes, but is not limited to, ITO, FTO, ATO, AZO, or mixtures thereof.
  • the metal materials include, but are not limited to, Al, Ag, Cu, Mo, Au, or their alloys; among the metal materials, their forms include but are not limited to dense films, nanowires, nanospheres, nanometers Rods, nano cones, nano hollow spheres, or their mixtures; the cathode is Ag, Al.
  • the quantum dot light-emitting layer has a thickness of 8-100 nm.
  • the hole transport layer has a thickness of 10-150 nm.
  • the electron transport layer has a thickness of 10-200 nm.
  • the electronic functional layer, the light-emitting layer, and the hole functional layer in the device can be designed with appropriate functional layers according to the characteristics of the device in the above embodiments.
  • a hole injection layer is grown on the surface of the anode
  • an electron transport layer is deposited on the quantum dot light-emitting layer, and a cathode electrode is evaporated on the electron transport layer to obtain an optoelectronic device.
  • step S10 the ITO substrate needs to undergo a pretreatment process, and the steps include: cleaning the ITO conductive glass with a detergent to preliminarily remove the stains existing on the surface, and then sequentially soaking in deionized water, acetone, anhydrous ethanol, and deionized water. Ultrasonic cleaning was carried out for 20 min to remove impurities on the surface, and finally dried with high-purity nitrogen to obtain the ITO positive electrode.
  • the step of growing the hole injection layer includes: preparing a metal oxide and other materials into a thin film in the QLED device by a solution method, a vacuum sputtering method, and a vacuum evaporation method; wherein, the solution method method Including inkjet printing, spin coating, spray printing (spray printing), slot-die printing (slot-die printing) or screen printing (screen printing) and the like.
  • the step of growing the hole transport layer includes: placing the ITO substrate on a spin coater, and using the prepared solution of the hole transport material to spin to form a film; adjusting the concentration of the solution and the spin coating speed and spin coating time to control the film thickness, followed by thermal annealing at an appropriate temperature.
  • the step of depositing the quantum dot light-emitting layer on the hole transport layer includes: placing the substrate on which the hole transport layer has been spin-coated on a spin coater, and spinning a solution of a prepared light-emitting substance with a certain concentration. Coating into a film, controlling the thickness of the light-emitting layer by adjusting the concentration of the solution, the spin coating speed and the spin coating time, about 20-60 nm, and drying at an appropriate temperature.
  • the step of depositing the electron transport layer on the quantum dot light-emitting layer includes: placing the substrate on which the quantum dot light-emitting layer has been spin-coated on a spin coater, and preparing a certain concentration of electron transport composite material
  • the solution is spin-coated to form a film by drip coating, spin coating, soaking, coating, printing, evaporation and other processes, and is controlled by adjusting the concentration of the solution, the spin coating speed (for example, the rotation speed is between 3000 and 5000 rpm) and the spin coating time.
  • the thickness of the electron transport layer is about 20 to 60 nm, and then annealed under the conditions of 150 ° C to 200 ° C to form a film, and the solvent is fully removed.
  • the steps of preparing the cathode include: placing the substrate on which each functional layer has been deposited into an evaporation chamber and thermally vapor-depositing a layer of 60-100 nm metal silver or aluminum as a cathode through a mask.
  • the method for preparing an optoelectronic device further includes encapsulating the laminated optoelectronic device; the curing resin used in the encapsulation is acrylic resin, acrylate resin or epoxy resin; resin curing adopts UV irradiation, Heat or a combination of both.
  • the encapsulation process can be done by conventional machine encapsulation or manual encapsulation. In the packaging process environment, the oxygen content and water content are both lower than 0.1ppm to ensure the stability of the device.
  • the method for preparing an optoelectronic device further includes, after encapsulating the optoelectronic device, introducing one or more processes including ultraviolet irradiation, heating, positive and negative pressure, applied electric field, and applied magnetic field; applying a process
  • the atmosphere can be air or an inert atmosphere.
  • the devices in the embodiments of the present application all adopt the ITO/HIL/HTL/QD/ETL/AL structure, and a certain heating treatment is performed after packaging.
  • the advantages of the technical solutions of the present application are explained in detail by comparing the collocation of different functional layers in the device.
  • the life test adopts the constant current method, under the constant current of 50mA/ cm2 , the silicon photosystem is used to test the brightness change of the device, and the time when the brightness of the device starts from the highest point and decays to 95% of the highest brightness is recorded LT95, Then extrapolate the 1000nit LT95S life of the device through the empirical formula.
  • This method is convenient for comparing the lifetime of devices with different brightness levels, and has a wide range of applications in practical optoelectronic devices.
  • the energy level test method of each material in the examples of the present application after spin-coating each functional layer material to form a film, the energy level test is carried out by UPS (ultraviolet photoelectron spectroscopy) method.
  • UPS ultraviolet photoelectron spectroscopy
  • Valence band top VB(HOMO): E HOMO E F-HOMO + ⁇ , where E F-HOMO is the difference between the material HOMO(VB) and the Fermi level, corresponding to the first occurrence of the low binding energy end in the binding energy spectrum the starting edge of a peak;
  • E LOMO E HOMO -E HOMO-LOMO
  • E HOMO-LOMO is the band gap of the material, obtained from UV-Vis (ultraviolet absorption spectrum).
  • this application sets up Examples 1 to 11, and compares the combinations of different HTLs and QDs to illustrate the empty space.
  • the effect of hole injection barrier on performance such as device lifetime.
  • the two kinds of quantum dots used in Examples 1 to 11 of the present application are: blue QD1 whose outer shell is CdZnS (the inner core is CdZnSe, the middle shell is ZnSe, the outer shell thickness is 1.5 nm, and the top energy level of the valence band is 6.2 eV),
  • the outer shell is a blue QD2 of ZnS (the inner core is CdZnSe, the intermediate shell is ZnSe, the ZnS shell thickness is 0.3 nm, and the valence band top energy level is 6.5 eV).
  • the blue QD3 with ZnSeS shell (the inner core is CdZnSe, the middle shell is ZnSe), the hole transport materials are P9 (E HOMO : 5.1 eV), P15 (E HOMO : 5.8 eV), and the hole injection layer is PEDOT:PSS (E HOMO : 5.1eV), the electron transport layer adopts a zinc oxide film layer with a surface hydroxyl content of less than or equal to 0.4, as shown in Table 1 below:
  • the ⁇ E EML-HTL barrier difference increases from 0.4eV to 0.7eV, and the device lifetime is significantly improved
  • the 1000nit LT95S life is increased from 0.72 to 6.29.
  • the device injection balance is optimized, and the device lifetime can be enhanced. It shows that reducing the hole injection efficiency by increasing the hole injection barrier can better balance the injection balance of holes and electrons in the light-emitting layer, and improve the luminous efficiency and luminous life of the device. In addition, it can be seen from Examples 7 to 11 that when the amount of hydroxyl groups on the surface of the ZnO thin film is less than or equal to 0.4, the device performance is better promoted.
  • this application sets up Examples 12 to 15, through the comparison of different HTL and HTL, to illustrate the effect of the ⁇ E HTL-HIL hole injection barrier on the device life. and other performance effects.
  • blue quantum dots with ZnS outer shells are used, and in Examples 14 to 15
  • the red quantum dots with the outer shell of ZnS are used, and the hole transport materials are P9 (E HOMO : 5.5 eV), P11 (E HOMO : 5.5 eV), P13 (E HOMO : 4.9 eV), PEDOT:PSS (E HOMO : 5.1 eV) and HIL2 (work function: 5.6 eV) are used for the hole injection layer, and surface hydroxyl groups are used for the electron transport layer 0.18 zinc oxide film layer, as shown
  • blue quantum dots whose outer shells are ZnS are ZnS (the inner core is CdZnSe, the middle shell is ZnSe, the outer shell thickness is 0.3 nm, and the top energy level of the valence band is 6.5 eV) are used, and in Examples 19 to 23
  • the red quantum dots with the outer shell of ZnS (the core is CdZnSe, the middle shell is ZnSe, the shell thickness is 0.3 nm, and the top energy level of the valence band is 6.5 eV) are used, and the hole transport materials are P9 (E HOMO : 5.5 eV), P13 (E HOMO : 4.9 eV), TFB (E HOMO : 5.4 eV), the hole injection layer adopts PEDOT: PSS (E HOMO : 5.1 eV), HIL1-1 (work function: 5.4 eV) and HIL1-2 (work function: 5.4 eV) letter: 5.3eV), and
  • red quantum dots whose outer shells are ZnS are used.
  • red quantum dots whose outer shells are ZnS are used.
  • red quantum dots whose outer shells are ZnS are used.
  • the electron transport layer adopts a zinc oxide film layer with a surface hydroxyl content of 0.18, as shown in Table 4:
  • the damage of the hole injection material of MoO 3 is effectively suppressed, so that the voltage rise of the device in the working process is compared with that of the organic material.
  • the hole injection layer material device has a significant reduction, and the measured time of the device life has also been effectively improved.

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  • Electroluminescent Light Sources (AREA)

Abstract

La présente demande divulgue un dispositif photoélectrique, comprenant une anode, une couche de transport de trous, une couche électroluminescente à points quantiques, une couche de transport d'électrons et une cathode qui sont empilées en séquence, la couche électroluminescente à points quantiques comprenant un matériau à points quantiques ayant une structure cœur-écorce, et un matériau de couche de coque externe du matériau à points quantiques et un matériau transporteur de trous ayant une différence de niveau d'énergie supérieure de bande de valence supérieure ou égale à 0,5 eV ; et la couche de transport d'électrons comprend une couche de film mince d'oxyde de zinc ayant une quantité d'hydroxyle de surface inférieure ou égale à 0,4. Dans le dispositif photoélectrique décrit dans la présente demande, une barrière ≥ 0,5 eV est construite entre le matériau de couche de coque externe du matériau à points quantiques et le matériau transporteur de trous pour réduire l'efficacité d'injection de trous, et les rendements de transport et d'injection d'électrons sont améliorés par la couche de film mince de transport d'électrons d'oxyde de zinc avec une quantité d'hydroxyle de surface ≤ 0,4, de telle sorte que les taux d'injection de trous et d'électrons dans le dispositif électroluminescent sont équilibrés, l'efficacité de recombinaison des électrons et des trous est améliorée, l'accumulation de charge provoquée par une injection non équilibrée de porteuses est évitée, et l'efficacité électroluminescente et la durée de vie du dispositif électroluminescent sont améliorées.
PCT/CN2021/141798 2020-12-31 2021-12-27 Dispositif photoélectrique WO2022143567A1 (fr)

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