CN111740019A - Halide perovskite optoelectronic devices based on polar interfaces - Google Patents

Abstract

A halide perovskite photoelectric device based on a polar interface belongs to the technical field of novel energy, materials and electronics. The present invention is directed to a polar interface based halide perovskite optoelectronic device that efficiently matches perovskite material and charge transport material together through a polar interface material. The preparation process of the perovskite luminescent thin film luminescent device comprises the following steps: preparing a substrate with a polar interface; and transferring the substrate with the evaporated polar interface to a glove box filled with high-purity nitrogen to spin-coat the perovskite thin film to obtain the perovskite light-emitting thin film light-emitting device. The invention introduces a polar interface in the preparation process of the perovskite material and the photoelectric device, so that the charge transport material with excellent performance and the perovskite material are mutually compatible and effectively matched, the interface can regulate and control the potential barrier of the charge transport material and the perovskite, and can regulate and control the crystallization process of the perovskite on the substrate or the transport material to regulate and control the crystallization quality, and finally, the performance of the perovskite material and the photoelectric device is optimized or regulated and controlled.

Description

Halide perovskite optoelectronic devices based on polar interfaces

technical field

The invention belongs to the technical fields of novel energy, materials and electronics.

Background technique

Metal halide perovskites, as a solution-processed material, exhibit remarkable optoelectronic properties, including high carrier mobility, long carrier diffusion length, tunable band gap, high luminescence efficiency, and ultra-high luminous efficiency. Narrow light-emitting bandwidth and other advantages. With the rapid development of halide perovskite materials, the excellent properties of perovskites have made great progress in many applications, such as solar cells, photodetectors, light-emitting diodes and other optoelectronic devices. After the first perovskite solar cell was reported in 2009, perovskite materials have developed rapidly in the field of solar cells, and their energy conversion efficiency has exceeded 25% in 2019. After the first perovskite light-emitting device was reported in 2014, the performance of perovskite-based light-emitting devices has rapidly improved in less than 5 years, and its external quantum efficiency has exceeded 20% in 2018. The rapid development of its device performance is due to the fact that perovskite has received extensive attention from researchers in many fields, and people are committed to improving the overall performance of perovskite materials. At present, perovskite devices have absorbed valuable experience in many research fields, including organic In many fields such as light-emitting diodes, quantum dot light-emitting diodes, semiconductor polysilicon batteries, lithium batteries, polymer materials, etc., the surface passivation and modification of perovskite and transmission materials have been made through various efforts, so that the device can effectively suppress the non-radiation inside the device. Recombination and enhanced radiation recombination, so as to achieve a substantial increase in the performance of the device.

At present, the structure of the device has also evolved from the original sandwich functional layer to a multi-layer functional layer. Taking the five-layer structure as an example, it includes electrodes, hole transport materials (electron blocking materials), light-emitting materials (absorbing materials in batteries), electron Transport materials (hole blocking materials), electrodes. The selection of functional materials has a positive effect on the improvement of device performance. For materials with excellent performance in other fields, they cannot be directly applied to the structure of perovskite devices. Active improvements are still needed to adapt to the structure of perovskite devices. For example, in the solution method Dealing with the mutual solubility of solvent and solute among multiple functional materials involved in perovskite light-emitting devices is a problem that is expected to be solved.

For the currently reported functional materials with outstanding performance in the OLED field, there are still many materials that cannot directly prepare high-performance perovskite LEDs by solution methods, and further optimization is required to apply them in the perovskite field. For example, in the process of fabricating light-emitting diodes, it is difficult for halide perovskites to be deposited on it by solution method for the highly hydrophobic hole transport materials conjugated polymers TFB, Poly-TPD and PFO. The researchers used a variety of methods to achieve efficient deposition of perovskites onto conjugated polymers. One method is to pass a Plasma plasma cleaner or a plasma cleaner on the surface of hole transport materials such as TFB, Poly-TPD, etc., before depositing the perovskite. UV-Ozone cleaning machine performs surface treatment, thereby changing the surface of the hole transport material from hydrophobic to hydrophilic. However, the use of plasma surface treatment can cause damage to the polymer surface resulting in degradation of the conductive properties. Another method is to deposit a very thin PVK onto a conjugated polymer and then deposit the perovskite, but PVK can be dissolved in DMF and DMSO, which are very commonly used perovskite precursor solutions. It will lead to the dissolution of part of PVK when perovskite is deposited on PVK, resulting in the formation of a blended interface between PVK and perovskite, which will affect the growth quality of perovskite, introduce interface defects and crystal growth defects, and then limit the reliability of the device preparation process. sex, stability.

SUMMARY OF THE INVENTION

The object of the present invention is a polar interface-based halide perovskite optoelectronic device that efficiently matches a perovskite material and a charge transport material together through a polar interface material.

The preparation process of the perovskite light-emitting thin film light-emitting device of the present invention:

Preparation of the substrate: firstly, ultrasonic cleaning was carried out for 15 minutes in seven steps of deionized water, acetone, isopropanol, deionized water, isopropanol, deionized water, and isopropanol, and then the substrate was placed in UV- Ozone cleaning was performed for 15 minutes in an Ozone ozone cleaning machine, and then the substrate was transferred to a vacuum coating machine for polar interface evaporation. The evaporation process in the vacuum coating machine was all completed in a glove box. Substrates coated with polar interfaces;

The substrate with polar interface was evaporated and then transferred to a glove box filled with high-purity nitrogen. The perovskite precursor solution sucked by the pipette is dropped onto the substrate with polar interface, and the vacuum spin coater spins at 3000 rpm/s for 60 s, and then spins to complete the perovskite lining. The bottom was placed on a hot stage for annealing at 60 °C for 10 min to obtain a perovskite light-emitting thin film light-emitting device.

The polar interface material of the present invention is composed of a variety of compounds, including polar interface materials that can form compounds in different periods, polar interface materials that can form compounds between different groups, strong polar interface materials that can form compounds between different groups, Other interface materials that cooperate with perovskite materials.

The polar interface materials that can form compounds during different periods of the present invention include metal oxide material interfaces ZrO ₂ , V ₂ O ₅ , Al ₂ O ₃ , NiO, MoO ₃ , ZnO, MgO, NiO, SnO ₂ ; The polar interface materials that form compounds include carbonate metal compound materials Li ₂ CO ₃ , Na ₂ CO ₃ , Cs ₂ CO ₃ ; the strongly polar interface materials that can form compounds between different groups include metal fluoride material interfaces LiF, NaF, KF, RbF, CsF, MgF ₂ , CaF ₂ ; other interface materials that cooperate with perovskite materials include PTFE, piezoelectric films, and piezoelectric ceramics.

The present invention prepares a conductive perovskite light-emitting thin film light-emitting device with ITO:

a. Conductive substrate with ITO: ITO sputters the ITO raw material onto the substrate through magnetron sputtering technology, places the substrate on the substrate stage with a mask, and uses the mask to align the substrate Partial shading is carried out, and part of the exposed ITO material is sputtered;

b. Cleaning treatment of conductive substrates: For conductive substrates, pretreatment is required. First, use deionized water, acetone, isopropanol, deionized water, isopropanol, deionized water, and isopropanol. Each step is ultrasonically cleaned for 15 minutes, and then the conductive substrate is placed in a UV-Ozone ozone cleaning machine for 15 minutes of ozone cleaning;

c. Preparation of charge transport material film: place the cleaned conductive substrate in a glass petri dish, and transfer the glass petri dish into a nitrogen glove box through the transition chamber of the glove box, and then place the conductive substrate in a glass petri dish. On the vacuum spin coater in the nitrogen glove box, the charge transport material is dissolved in the solvent, and the charge transport material solution is drawn with a pipette and uniformly coated on the conductive substrate, and the charge transport material completely coats the ITO. Turn on the vacuum spin coater button and spin at 3000rpm for 60s to form a film of the charge transport material. After the spin coating of the charge transport material film is completed, place the conductive substrate covered with the charge transport material on a hot stage for a high temperature of 120°C. Annealing for 10 minutes, and finally forming a thin film of charge transport material coated with ITO on the conductive substrate;

d. Evaporation of polar interface materials: Open the door of the vacuum coating machine in the glove box in step 1, and place the conductive substrate prepared with the charge transport material removed from the hot stage into a glass petri dish. The transition bin is transferred into the glove box with the vacuum coating machine, and the conductive substrate prepared with the charge transport material is taken out, placed on the evaporation substrate stage in the vacuum coating machine, adjusted the position of the evaporation substrate stage, and closed. baffle plate below the substrate stage;

e. Spin-coating halide perovskite thin film: During spin-coating, place the conductive substrate evaporated with polar interface material and covered with charge-transporting material on a vacuum spin-coater, and use a pipette to absorb calcium halide. The titanium ore precursor solution was uniformly coated on the conductive substrate evaporated with polar interface material and covered with charge transport material, and the button of the vacuum spin coater was turned on and spun at 5000 rpm for 60 s to form halide perovskite. The conductive substrate covered with halide perovskite, evaporated with polar interface material, and covered with charge transport material was placed on a hot stage for high temperature annealing at 90°C for 10 minutes;

f. Evaporation of cathode charge transport material: The annealed conductive substrate covered with halide perovskite, evaporated with polar interface material, and covered with charge transport material is placed in a glass petri dish and transferred The warehouse is transported into a glove box with a vacuum coating machine, taken out from a glass petri dish and placed on the evaporation substrate stage in the vacuum coating machine, adjust the position of the evaporation substrate stage, and close the baffle below the substrate stage; The film thickness meter shows the evaporation rate of the charge transport material detected by the quartz crystal oscillator. After waiting for the evaporation rate of the charge transport material displayed by the film thickness meter to stabilize, the evaporation rate is stabilized at 0.05nm/s, and the substrate stage in the vacuum coating machine is turned on. The baffle below, the charge transport material with uniform evaporation rate can be uniformly deposited on the conductive substrate covered with halide perovskite, evaporated with polar interface material, and covered with charge transport material;

g. Evaporation electrode: After the charge transport material is evaporated, place it on the metal mask in the vacuum coating machine, and display the evaporation rate of the electrode detected by the quartz crystal oscillator through the film thickness meter. Wait for the film thickness meter After the evaporation rate of the displayed electrode is stabilized, the evaporation rate is stabilized at 0.2 nm/s, and the baffle below the substrate stage in the vacuum coating machine is opened, and the electrode with uniform evaporation rate is uniformly deposited to the surface covered with charge transport material, halide perovskite , Evaporated on a conductive substrate with polar interface materials and covered with charge transport materials.

The preparation method of the polar interface on the substrate of the present invention adopts magnetron sputtering, MOCVD, ALD, spraying, printing or chemical synthesis method, and the thickness ranges from 0.1 nm to 1000 nm.

The invention changes the polarity of the polar interface material by regulating materials with different electronegativity differences, or regulates the non-polar interface to be a polar interface, and finally regulates the final performance of the device by changing the polarity of the material interface.

The polar material interface of the present invention is applied to various optoelectronic devices, including solar cells, light-emitting diodes, detectors, fluorescent films, phosphors, semiconductor transistors, lasers and other optoelectronic devices and materials.

The polar material interface of the present invention can be applied to define the effective working area of perovskite materials or devices, and then define different working patterns, which can be extended to perovskite materials and optoelectronic devices based on different patterns.

The invention introduces a polar interface in the preparation process of the perovskite material and the optoelectronic device, so that the charge transport material with excellent performance and the perovskite material are compatible and effectively matched with each other, and the interface can not only regulate the potential barrier between the charge transport material and the perovskite , the crystallization process of perovskite on substrates or transport materials can also be regulated to control the crystallization quality, and finally optimize or tune the performance of perovskite materials and optoelectronic devices. The method of controlling perovskite materials and optoelectronic devices using polar interfaces can be extended to a variety of optoelectronic devices and materials, including solar cells, light-emitting diodes, detectors, fluorescent films, phosphors, semiconductor transistors, lasers and other optoelectronic devices in terms of materials.

Description of drawings

Fig. 1 is the perovskite structure of the polar interface of common substrate of the present invention;

Fig. 2 is the polar interface perovskite photoelectric device structure of the conductive substrate with ITO of the present invention;

Fig. 3 is the hydrophilic experiment preparation flow chart of the polar interface of the present invention;

Fig. 4 is the surface tension contrast figure before and after adding interface of the present invention;

Fig. 5 is the present invention adopts polar interface and plasma to carry out surface treatment flow chart respectively;

Fig. 6 is the topography of the charge transport material using polar interface and plasma surface treatment in the present invention;

Fig. 7 is the SEM flow chart of the spin-coated perovskite luminescent film of the present invention;

8 is a SEM image of the film-forming morphology of the perovskite of the present invention on different interfaces;

Fig. 9 is the Wavelength flow chart of the spin-coated perovskite luminescent film test of the present invention;

Figure 10 is a perovskite luminescence spectrum when different materials are used as an interface;

Figure 11 is the flow chart of the Absorbance test of the spin-coated perovskite luminescent film;

Figure 12 is a schematic diagram of the effect of different materials on the absorption spectrum of perovskite when used as an interface;

Fig. 13 is the XRD flow chart of the spin-coated perovskite luminescent film test;

Fig. 14 is the thin film XRD patterns of perovskite on different interfaces;

Figure 15 is a flow chart of the photo-induced quantum efficiency PLQE test at different interfaces;

Fig. 16 is a graph showing the change of PLQE of perovskite with interfacial electronegativity of different polarities;

Figure 17 is a flow chart of the preparation steps of perovskite on different charge transport materials;

Figure 18 is a graph showing the fluorescence lifetime of perovskite on different charge transport materials;

Fig. 19 is the preparation flow chart of the interface of different thickness;

Fig. 20 is a graph showing the effect of interfaces of different thicknesses on charge injection capability;

FIG. 21 is a flow chart of the fabrication of light-emitting diode devices;

Figure 22 is a graph of device efficiency based on polar interface transport materials and other transport materials.

Detailed ways

The preparation process of the perovskite light-emitting thin film light-emitting device of the present invention:

Preparation of the substrate: firstly, ultrasonic cleaning was carried out for 15 minutes in seven steps of deionized water, acetone, isopropanol, deionized water, isopropanol, deionized water, and isopropanol, and then the substrate was placed in UV- Ozone cleaning was performed for 15 minutes in an Ozone ozone cleaning machine, and then the substrate was transferred to a vacuum coating machine for polar interface evaporation. The evaporation process in the vacuum coating machine was all completed in a glove box. Substrates coated with polar interfaces;

The substrate with polar interface was evaporated and then transferred to a glove box filled with high-purity nitrogen. The perovskite precursor solution sucked by the pipette is dropped onto the substrate with polar interface, and the vacuum spin coater spins at 3000 rpm/s for 60 s, and then spins to complete the perovskite lining. The bottom was placed on a hot stage for annealing at 60 °C for 10 min to obtain a perovskite light-emitting thin film light-emitting device.

The polar interface material of the present invention is composed of a variety of compounds, including polar interface materials that can form compounds in different periods, polar interface materials that can form compounds between different groups, strong polar interface materials that can form compounds between different groups, Other interface materials that cooperate with perovskite materials.

The polar interface materials that can form compounds during different periods of the present invention include metal oxide material interfaces ZrO ₂ , V ₂ O ₅ , Al ₂ O ₃ , NiO, MoO ₃ , ZnO, MgO, NiO, SnO ₂ ; The polar interface materials that form compounds include carbonate metal compound materials Li ₂ CO ₃ , Na ₂ CO ₃ , Cs ₂ CO ₃ ; the strongly polar interface materials that can form compounds between different groups include metal fluoride material interfaces LiF, NaF, KF, RbF, CsF, MgF ₂ , CaF ₂ ; other interface materials that cooperate with perovskite materials include PTFE, piezoelectric films, and piezoelectric ceramics.

In order to solve the problem of mismatch between the two materials in perovskite, the relevant research experience in the field of inorganic semiconductors and materials is used for reference. At present, when epitaxial growth is carried out in group III and V inorganic semiconductors, for two different semiconductor materials, when the lattice parameters of the two materials differ greatly, it will lead to difficulty in direct matching. In the heterojunction, a large number of interface states will be generated at the interface due to the difference of the lattice constant, which has a great influence on the band structure and electron transport of the heterojunction. Therefore, in order to eliminate the problem of difficult growth of materials caused by interface defects, and to make the two functional materials in good contact, the Schottky contact between the two materials can be improved by introducing polar materials or activated materials between the two materials. for ohmic contact. The introduction of polar materials or active materials makes the lattice mismatch of the two functional materials low, the interface state density is low, and the interface barrier is low, thereby increasing the electron injection and transport capabilities. cooperate effectively. In the preparation process of metallic glass, due to the mismatch between the lattices of glass and metal, the stability of the prepared metallic glass will not be good enough. Therefore, a small amount of transition metal or graphene is introduced between the glass and the metal for lattice matching, which can improve the stability of the prepared metallic glass. A more stable lattice structure is achieved. Based on this, in view of the mismatch between perovskite and perovskite materials with excellent performance, we can consider introducing functional materials or activation materials to effectively match perovskite and charge transport materials to reduce the interface barrier. , to increase the electronic transport capacity.

Since perovskite is a strong polar material, according to the similar compatibility principle, perovskite can cooperate well with strong polar materials, and the new material introduced at the same time cannot change the inherent composition of perovskite, so some different strong polar materials are selected. The interfacial material is introduced into the charge transport material and the perovskite material for lattice matching. Different transport materials are required for in situ growth of perovskites, but the transport materials with excellent performance are incompatible with perovskites, resulting in the barrier of charge transport at the interface between perovskite and transport materials. By using ultra-thin strong polar materials Deposition on the polymer hole transport material can ensure that the perovskite is effectively grown on the polymer hole transport material covered with the polar interface, and the use of the polar material interface can increase or control the quality of the crystal growth and control the perovskite The carrier lifetime of the ore thin film, thereby regulating the stability of the thin film and the performance of perovskite-based devices. The method of using polar interfaces to modulate the performance of perovskite films or devices can be extended to other optoelectronic devices, including solar cells, light-emitting diodes, detectors, fluorescent films, phosphors, semiconductor transistors, lasers and other optoelectronic devices and materials. , in order to prepare devices with better performance.

At present, perovskite materials and optoelectronic devices are still insufficient in terms of optoelectronic properties and stability. The specific reasons are two aspects. On the one hand, the outstanding performance of substrates, charge transport materials and perovskite materials cannot be perfectly matched, which limits the preparation. The optimal performance of perovskite optoelectronic devices, for example, for optoelectronic devices prepared by solution method, the charge transport material and perovskite material have interfacial mutual dissolution phenomenon, resulting in imperfect interface and affecting the performance of each functional material; on the other hand, The perovskite material itself has problems, which are manifested in poor crystal growth quality, many grain boundaries and interface defects, which ultimately limit the performance of perovskite materials and optoelectronic devices. At present, various methods can be used in the preparation process to optimize the perovskite crystal quality. , and ultimately improve or tune the performance of perovskite materials and optoelectronic devices. In view of the incompatibility between perovskite materials and charge transport materials, a commonly used method is to use a Plasma surface cleaner or a UV-Ozone surface cleaner to activate the surface of the charge transport material, and the treated surface of the charge transport material It is activated, but the surface treatment will destroy the group structure on the surface of the transport material. Although it can be better combined with the perovskite surface groups, the problem is that the perovskite is deposited on the surface of the activated charge transport material. The properties of titanium ore itself, such as PLQE , will decrease to varying degrees, and the charge transport ability of charge transport materials will also decrease to varying degrees. Another method is to use a non-orthogonal solvent to introduce an intermediate material as a transition material between the perovskite material and the charge transport material. Since the dissolution of the orthogonal solvent and the perovskite material will cause the performance of the perovskite to decrease, the perovskite solvent dissolves. The charge transport material will lead to the decrease of the charge transport ability of the transport material. No matter which solvent it is, the material will be damaged to varying degrees, which means that for different researchers and different operating methods, the prepared devices and the target performance are very different. , the result is poor device repeatability, high fabrication complexity, and large batch difficulty.

The technical problem to be solved by the present invention is that, on the one hand, the effective matching of the perovskite material and the charge transport material is achieved, which is embodied in the low interface barrier and the good charge transport ability; The transport material or perovskite material dissolves in each other, which is embodied in avoiding mutual dissolution between functional materials. The use of polar interfaces as a means of regulating perovskite materials and optoelectronic devices can affect the final device performance through two aspects. At the same time, each functional material can exert its outstanding advantages and ultimately regulate the performance of the device; on the other hand, it is to regulate the crystal growth process. By regulating the morphology of the perovskite, the density of defect states, etc., it can improve or regulate the luminescence performance, photovoltaic performance, and carrier injection. , the purpose of carrier transport, and ultimately control the overall performance of the device. The purpose of the present invention is to propose a method for regulating perovskite materials and optoelectronic devices based on polar interfaces, which can achieve two purposes. , the interface material introduced by it makes the charge transport material with excellent performance and perovskite material compatible with each other, and will not bring about performance degradation; Thermal evaporation, magnetron sputtering, MOCVD, ALD, spraying, printing, chemical synthesis and other physical or chemical methods, deposited on perovskite or charge transport materials, the deposited material will not dissolve its deposition interface, while isolating The charge transport material and the perovskite material are in direct contact with the solvent, so there is no mutual dissolution process of the charge transport material and the perovskite material, so that the charge transport material and the perovskite material are effectively matched to ensure their excellent properties.

Figure 1 shows the perovskite structure at the polar interface of the common substrate. The perovskite is deposited on the substrate covered with the polar interface, where L1 is the perovskite film, L2 is the polar interface, and L3 is the substrate ( In the following, the quartz plate is used as the substrate material to be described).

The size of the quartz wafer substrate L3 is 12mm*12mm. The quartz wafer is ultrasonically cleaned with 7 steps of deionized water, acetone, isopropanol, deionized water, isopropanol, deionized water, and isopropanol for 15 minutes before use. . The cleaned quartz wafers were placed in a UV-Ozone ozone cleaning machine for 15 minutes of ozone cleaning, and then the quartz wafer substrates were transferred to a glove box filled with high-purity nitrogen, and then transferred to a vacuum coating machine for polar interface evaporation experiments. .

The polar interfaces L_2 are NiO, MoO ₃ , ZnO, MgO, Li ₂ CO ₃ , Na ₂ CO ₃ , LiF, CaF ₂ , NaF, KF, CsF, MgO (in the specific examples, the comparative distillation of these materials was carried out). Plating experiments, all listed here), as a comparison quartz wafer substrate does not evaporate the polar interface. The pressure of vacuum evaporation is 5 x 10 ^-4 Pa, the evaporation rate is measured by a quartz crystal oscillator, the evaporation rate is 0.01 nm/s, the thickness of the polar interface evaporation is 1 nm, and the quartz with polar interface is evaporated The sheets were then transferred to a glove box filled with high purity nitrogen for spin-coated perovskite films.

The L1 component of the perovskite film is halide perovskite, and the perovskite precursor solution is PEA _n CsPb _n Br _3n+1 , which consists of 110 mg of PbBr ₂ (lead bromide), 64 mg of CsBr (cesium bromide) and 24 mg of PEABr (2-phenethylammonium bromide), dissolved in 1 mL of DMSO (dimethyl sulfoxide) solution at a molar ratio of 1:1:0.4, the solution concentration was 0.3 mol/L, The solution was placed on a 60°C hot stage and stirred for 1 h. When spin-coating perovskite, put the evaporated quartz sheet with polar interface on the vacuum spin coater, suck 30uL of perovskite precursor solution with a 100uL pipette, and drop it onto the evaporated quartz sheet with polar interface, The vacuum spin coater was used for spin coating at 3000 rpm/s for 60 s, and then the perovskite-coated quartz sheet was placed on a hot stage for annealing at 60 °C for 10 min to obtain a perovskite luminescent film with a thickness of 35 nm.

Finally, the perovskite thin film L1, the polar interface L2, and the substrate L3 constitute a light-emitting device, but this structure is a non-conductive substrate.

Figure 2 shows the structure of a polar interface perovskite optoelectronic device with a conductive substrate with ITO.

The substrate selected for the preparation of the polar interface-based perovskite light-emitting device is a quartz plate without ITO (indium tin oxide), and the substrate selected for the preparation of the polar interface-based perovskite optoelectronic device is a substrate with ITO (oxide). Indium tin) quartz wafer, the preparation process of the two device structures are as follows:

1. Preparation of perovskite light-emitting devices based on polar interfaces.

The substrate selected for the polar interface-based perovskite light-emitting device is a quartz wafer substrate L3 without ITO (indium tin oxide) L6. The device preparation process is as follows:

Step 1, cleaning the non-conductive substrate L3: the non-conductive substrate quartz plate L3 is composed of SiO ₂ , the size is 12mm*12mm, and the thickness is 1mm. The non-conductive substrate L3 needs to be pre-treated before use. First, use seven steps of deionized water, acetone, isopropanol, deionized water, isopropanol, deionized water, and isopropanol for 15 minutes of ultrasound respectively. After cleaning, the substrate was placed in a UV-Ozone ozone cleaning machine for 15 minutes of ozone cleaning.

Step 2: Evaporate polar interface material L2: place the cleaned non-conductive substrate L3 in a glass petri dish, and transfer the glass petri dish into a nitrogen glove box with a vacuum coater through the transition chamber of the glove box . Open the door of the vacuum coating machine in the glove box, take out the non-conductive substrate L3 from the glass petri dish, and place it on the evaporation substrate stage in the vacuum coating machine, adjust the position of the evaporation substrate stage, and close the substrate Baffle below the table.

Transfer the polar interface material L2 into the vacuum coating machine, put it into the thermal evaporation crucible, adjust the position of the thermal evaporation crucible, align the evaporation substrate table on which the non-conductive substrate L3 is placed, and close the door of the vacuum coating machine. . Because the polar interface material is easily affected by water vapor, oxygen and other gases in the atmosphere, resulting in a decrease in purity and performance, the polar interface material L2 is stored in a glove box filled with high-purity nitrogen, and the polar interface material L2 is stored in a glove box filled with high-purity nitrogen. The interface material L2 is conveyed into the vacuum coater.

The baffle below the substrate stage is to prevent the polar interface material from being directly evaporated on the non-conductive substrate L3. During the evaporation process, the evaporation rate and material purity of the material have a great influence on the prepared polar interface film L2. Therefore, it is necessary to wait for the detection rate of the quartz crystal in the vacuum coating machine to stabilize before opening the baffle below the substrate stage. The polar interface material L2 with a stable evaporation rate can be uniformly evaporated onto the non-conductive substrate L3.

After turning on the mechanical pump and molecular pump connected to the vacuum coating machine, wait for the pressure of vacuum evaporation to drop to 5 x 10 ^-4 Pa, then turn on the power supply of the thermal evaporation crucible, and the power supply of the thermal evaporation crucible will gradually heat the thermal evaporation crucible to prevent loading into the thermal evaporation crucible. The heating of the thermal evaporation crucible is too fast, resulting in the splash of the polar interface material L2. Gradual heating of the thermal evaporation crucible helps to form a uniform evaporation rate of the polar interface material L2, so it is necessary to gradually heat the thermal evaporation crucible.

The evaporation rate of the polar interface material L2 detected by the quartz crystal oscillator is displayed by the film thickness meter. After the evaporation rate of the polar interface material L2 displayed by the film thickness meter is stabilized, the evaporation rate is stabilized at 0.01nm/s, and the vacuum is turned on. In the baffle plate below the substrate stage in the coating machine, the polar interface material L2 with uniform evaporation rate can be uniformly evaporated onto the non-conductive substrate L3, and the polar interface evaporation thickness is 1 nm.

After evaporating the polar interface material L2, close the baffle plate below the substrate stage in the vacuum coating machine, close the molecular pump and mechanical pump connected to the vacuum coating machine, and then wait for the pressure in the vacuum coating machine to return to atmospheric pressure, and turn on the vacuum coating machine. The door is opened, and the non-conductive substrate L3 on which the polar interface material L2 is vapor-deposited is taken out from the substrate stage. It was then placed into a glass petri dish, which was transferred through a transition chamber to a glove box with a vacuum spin coater, followed by spin coating of the halide perovskite thin film L1.

Step 3, spin coating halide perovskite L1: the non-conductive substrate L3 with polar interface material L2 is evaporated and then transferred to a glove box with a vacuum spin coater through a glass petri dish to spin a halide perovskite film , when spin coating perovskite, put the substrate with polar interface on the vacuum spin coater, suck the perovskite precursor solution with a pipette, drop it on the substrate with polar interface, vacuum The spin-coater spins at 3000 rpm/s for 60 s, and then the spin-coated perovskite substrate is placed on a hot stage for annealing at 60 °C for 10 min to obtain a perovskite thin film device.

Finally, a halide perovskite light-emitting device based on a polar interface is formed. The halide perovskite light-emitting film is excited by excitation light higher than the luminescence energy of the halide perovskite, and the halide perovskite can emit fluorescence. Based on this method Fluorescent films can also be prepared that can also be used on flexible substrates.

2. Preparation of perovskite optoelectronic devices based on polar interfaces.

The substrate selected for the polar interface-based perovskite optoelectronic device is a quartz sheet with ITO (indium tin oxide) L6, and the preparation process leaves:

Step 1, prepare a conductive substrate with ITO (indium tin oxide) L6: the conductive substrate is composed of ITO (indium tin oxide) L6 and a quartz wafer substrate L3, the composition of the quartz wafer is SiO ₂ , and the size It is 12mm*12mm, and its thickness is 1mm. ITO can sputter the ITO raw material onto the quartz wafer by the magnetron sputtering technology. The thickness of ITO is 185nm. When sputtering ITO (indium tin oxide) L6, the quartz wafer substrate L3 is placed on the substrate stage with the mask. The quartz wafer substrate L3 can be partially shielded by a mask. The exposed part can be sputtered with ITO material, and the unexposed part cannot be sputtered with ITO material. The mask can be used to achieve center sputtering on the quartz wafer substrate L3. The shape of 8*12mm rectangular ITO (indium tin oxide) L6 is shot, with 2mm blank space on each side, and the blank position is not covered by ITO.

Step 2, the cleaning treatment of the conductive substrate: the conductive substrate needs to be pre-treated, firstly use deionized water, acetone, isopropanol, deionized water, isopropanol, deionized water, isopropanol The seven steps were ultrasonically cleaned for 15 minutes respectively, and then the conductive substrate was placed in a UV-Ozone ozone cleaning machine for 15 minutes of ozone cleaning.

Step 3: Prepare the charge transport material L7 film: place the cleaned conductive substrate into a glass petri dish, and transfer the glass petri dish into the nitrogen glove box through the transition chamber of the glove box, and then transfer the conductive substrate to the glass petri dish. Placed on a vacuum spin coater in a nitrogen glove box. The charge transport material L7 is dissolved in the solvent, and 30uL of the charge transport material solution is drawn with a 100uL pipette and evenly coated on the conductive substrate. The charge transport material L7 can completely coat the ITO (indium tin oxide) L6. , turn on the vacuum spin coater button and spin at 3000rpm for 60s to form a thin film of the charge transport material L7. After the spin coating of the charge transport material L7 film is completed, place the conductive substrate covered with the charge transport material L7 on the hot stage. A high temperature annealing at 120°C is performed for 10 min, and finally a charge transport material film L7 coated with ITO (indium tin oxide) L6 is formed on the conductive substrate.

Step 4: Evaporating the polar interface material L2: Open the door of the vacuum coating machine in the glove box, place the conductive substrate prepared with the charge transport material L7 removed from the hot stage into a glass petri dish, and pass The transition bin is transferred into the glove box with the vacuum coating machine, and the conductive substrate prepared with the charge transport material L7 is taken out, placed on the evaporation substrate stage in the vacuum coating machine, and the position of the evaporation substrate stage is adjusted. Close the shutter under the substrate stage.

Transfer the polar interface material L2 into the vacuum coating machine, put it into the thermal evaporation crucible, adjust the position of the thermal evaporation crucible, align the evaporation substrate stage with the conductive substrate on which the charge transport material L7 is placed, and turn off the vacuum The door of the coating machine. Since the polar interface material is easily affected by water vapor, oxygen and other gases in the atmosphere, resulting in a decrease in purity and performance, the polar interface material is stored in a glove box filled with high-purity nitrogen, and the material is transferred into the in the vacuum coating machine.

The baffle below the substrate stage is to prevent the polar interface material L2 from being directly evaporated on the conductive substrate prepared with the charge transport material L7, because during the evaporation process, the evaporation rate and material purity of the material have an impact on the polarity of the preparation. The interface material L2 has a great influence, so it is necessary to wait for the detection rate of the quartz crystal oscillator in the vacuum coating machine to stabilize before opening the baffle under the substrate stage. The polar interface material L2 with a stable evaporation rate can be uniformly evaporated to cover the charge transport material. on the conductive substrate of L7.

After turning on the mechanical pump and molecular pump connected to the vacuum coating machine, wait for the pressure of vacuum evaporation to drop to 5 x 10 ^-4 Pa, then turn on the power supply of the thermal evaporation crucible, and the power supply of the thermal evaporation crucible will gradually heat the thermal evaporation crucible to prevent loading into the thermal evaporation crucible. The heating of the thermal evaporation crucible is too fast, resulting in the splash of the polar interface material L2. Gradual heating of the thermal evaporation crucible helps to form a uniform evaporation rate of the polar interface material L2, so it is necessary to gradually heat the thermal evaporation crucible.

The evaporation rate of the polar interface material L2 detected by the quartz crystal oscillator is displayed by the film thickness meter. After the evaporation rate of the polar interface material L2 displayed by the film thickness meter is stabilized, the evaporation rate is stabilized at 0.01nm/s, and the vacuum is turned on. The baffle plate under the substrate stage in the coating machine, the polar interface material L2 with uniform evaporation rate can be uniformly deposited on the conductive substrate covered with the charge transport material L7, and the polar interface evaporation thickness is 1nm, and finally the polar interface material is formed. Interface material film L2.

After evaporating the polar interface material L2, close the baffle plate below the substrate stage in the vacuum coating machine, close the molecular pump and mechanical pump connected to the vacuum coating machine, and then wait for the pressure in the vacuum coating machine to return to atmospheric pressure, and turn on the vacuum coating machine. The chamber door is removed from the substrate stage, and the conductive substrate on which the polar interface material L2 is vapor-deposited and covered with the charge transport material L7 is taken out. It was then placed into a glass petri dish, which was transferred through a transition chamber to a glove box with a vacuum spin coater.

Step 5, spin coating the halide perovskite thin film L1: the perovskite thin film is a halide perovskite, and the halide perovskite is composed of different components, which can be dissolved in a polar solvent to form a precursor solution with different characteristics. During spin coating, the conductive substrate evaporated with polar interface material L2 and covered with charge transport material L7 is placed on a vacuum spin coater, and 30uL of halide perovskite precursor solution is drawn with a 100uL pipette to evenly coat it. Coated on the conductive substrate evaporated with polar interface material L2 and covered with charge transport material L7, turned on the button of the vacuum spin coater and spin-coated at 5000 rpm for 60 s to form a thin film of halide perovskite L1. The conductive substrate covered with halide perovskite L1, evaporated with polar interface material L2, and covered with charge transport material L7 was placed on a hot stage for annealing at a high temperature of 90 °C for 10 min, and a uniform halogenation was finally formed. material perovskite thin film L1.

Step 6: Evaporate cathode charge transport material L5: place the annealed conductive substrate covered with halide perovskite L1, evaporated with polar interface material L2, and covered with charge transport material L7 into a glass petri dish , and transfer it into the glove box with the vacuum coating machine through the transition bin, take it out from the glass petri dish and place it on the evaporation substrate stage in the vacuum coating machine, adjust the position of the evaporation substrate stage, and close the substrate stage. Bottom bezel.

Transfer the charge transport material L5 into the vacuum coating machine, put it into the thermal evaporation crucible, adjust the position of the thermal evaporation crucible, and align the L1 covered with halide perovskite, evaporated with polar interface material L2, and covered with charge transport. The conductive substrate of material L7, close the door of the vacuum coater. Since the charge transport material is easily affected by water vapor, oxygen and other gases in the atmosphere, resulting in a decrease in purity and performance, the charge transport material L5 is stored in a glove box filled with high-purity nitrogen, and then transferred into a vacuum when used. in the coating machine.

After turning on the mechanical pump and molecular pump connected to the vacuum coating machine, wait for the pressure of vacuum evaporation to drop to 5 x 10 ^-4 Pa, then turn on the power supply of the thermal evaporation crucible, and the power supply of the thermal evaporation crucible will gradually heat the thermal evaporation crucible to prevent loading into the thermal evaporation crucible. The heating of the thermal evaporation crucible is too fast, resulting in the sputtering of the charge transport material L5. Gradual heating of the thermal evaporation crucible helps to form a uniform evaporation rate of the charge transport material L5, so it is necessary to gradually heat the thermal evaporation crucible.

The evaporation rate of the charge transport material L5 detected by the quartz crystal oscillator is displayed by the film thickness meter. After the evaporation rate of the charge transport material L5 displayed by the film thickness meter is stabilized, the evaporation rate is stabilized at 0.05nm/s, and the vacuum coating machine is turned on. The baffle below the middle substrate stage, the charge transport material L5 with uniform evaporation rate can be uniformly deposited on the conductive substrate covered with halide perovskite L1, evaporated with polar interface material L2, and covered with charge transport material L7 On the above, the charge transport material L5 is evaporated to a thickness of 40 nm, and finally a thin film of the charge transport material L5 is formed.

Step 7: Evaporate the electrode L4: After the charge transport material L5 is evaporated, it is placed on the metal mask in the vacuum coating machine. The area of the formed halide perovskite film is 5.25 mm ² , and the electrode materials are composed of different kinds of metals and fluorides.

The evaporation rate of the electrode L4 detected by the quartz crystal oscillator is displayed by the film thickness meter. After the evaporation rate of the electrode L4 displayed by the film thickness meter is stabilized, the evaporation rate is stabilized at 0.2 nm/s, and the vacuum coating machine is turned on under the substrate stage. The baffle plate, the electrode L4 with uniform evaporation rate can be uniformly deposited on the conductive substrate covered with charge transport material L5, halide perovskite L1, evaporated with polar interface material L2, and covered with charge transport material L7. , the electrode L4 is vapor-deposited to a thickness of 100 nm, and finally a thin film of the electrode L4 is formed.

Finally, a halide perovskite optoelectronic device based on a polar interface is formed. By loading positive and negative voltages on ITO (indium tin oxide) L6 and electrode L4, the device can finally work under current driving.

The interface of polar materials is formed by different methods, such as thermal evaporation, magnetron sputtering, MOCVD, ALD, spraying, printing, chemical synthesis and other physical or chemical methods. The typical deposition thickness ranges from 0.1 nm to 1000 nm. Most functional materials are nanoscale devices, which can meet the functional requirements of current optoelectronic devices.

Compared with the perovskite films deposited directly on quartz or glass (SiO ₂ ), ITO, Si, FTO, PTFE and other substrates, there are many defects and poor crystal orientation, while those deposited on polar interfaces have fewer defects and higher film coverage. , which can realize the effective transition between the substrate or the transport material and the perovskite, and the polar interface plays the role of regulating the crystal growth process, which can control the crystal growth morphology, the crystal quality, and the luminous efficiency.

For compounds formed by elements of different groups in the periodic table, the material interface with the difference in electronegativity of the material between 0 and 2 is a polar material, and for the material with a difference in electronegativity greater than 2, it is a strongly polar material. The formed material interface can play a role in regulating the performance of perovskite materials and optoelectronic devices, such as regulating the growth size of perovskite crystals, luminescence wavelength, photoinduced external quantum efficiency PLQE , solar cell open-circuit voltage V _OC , short-circuit current J _SC , power conversion efficiency PCE and other parameters. The material interface can be composed of a variety of compounds, such as polar material interfaces that can form compounds during different periods, such as ZrO ₂ , V ₂ O ₅ , Al ₂ O ₃ , NiO, MoO ₃ , ZnO, MgO, NiO, SnO ₂ , etc. Metal oxide material interface. The polar material interface of compounds can be formed between different groups, such as Li ₂ CO ₃ , Na ₂ CO ₃ , Cs ₂ CO ₃ and other carbonate metal compound materials. Strongly polar material interfaces of compounds can be formed between different groups, such as LiF, NaF, KF, RbF, CsF, MgF ₂ , CaF ₂ and other metal fluoride material interfaces. Including other material interfaces that can cooperate with perovskite materials, such as PTFE, piezoelectric films, piezoelectric ceramics and other material interfaces.

The polarity of the material interface can be changed by adjusting, such as adjusting the polar interface to a non-polar interface, or adjusting the non-polar interface to a polar interface, and finally adjusting the final performance of the device by changing the polarity of the material interface.

The polar interface can regulate the luminescence properties of perovskite materials, reduce the fluorescence quenching of perovskite films by substrates or transport materials, and can control the fluorescence lifetime and photoinduced external quantum efficiency PLQE of the films.

The polar interface can effectively match the perovskite material and the charge transport material. For optoelectronic devices prepared based on the polar interface, the interface can regulate the injection barrier between various functional materials, and regulate or increase the charge transport capability, no matter in the PN type. Neither the material nor the PIN-type material restricts the flow of carriers, and can improve or regulate the carrier transport characteristics.

The introduction of polar interfaces can balance the transport rate of electrons and holes, and regulate the performance of perovskite optoelectronic devices, such as reducing the turn _- on voltage VT of light-emitting diodes, improving luminous brightness, and improving the fill factor FF , open-circuit voltage V OC _, Short-circuit current J _SC , power conversion efficiency PCE and other parameters, increase the detection sensitivity of the photodetector, etc.

Polar material interfaces can be applied to a variety of optoelectronic devices, including solar cells, light-emitting diodes, detectors, fluorescent films, phosphors, semiconductor transistors, lasers and other optoelectronic devices and materials.

working principle

At present, perovskite materials and optoelectronic devices are still insufficient in terms of optoelectronic properties and stability, because perovskites are polar ionic crystals. According to the principle of similarity compatibility, if there is a phenomenon of lattice mismatch, it will bring many problems. . The main reasons are two aspects. On the one hand, the outstanding performance of substrates, charge transport materials and perovskite materials cannot be perfectly matched, which limits the performance of the prepared perovskite optoelectronic devices. For example, for optoelectronic devices prepared by solution methods, the charge Transport materials and perovskite materials have interfacial dissolution phenomenon, which leads to imperfect interface and affects the performance of various functional materials; on the other hand, perovskite materials have problems, which are manifested in poor crystal growth quality, many grain boundaries and interface defects The performance of perovskite materials and optoelectronic devices is ultimately limited. At present, various methods can be used to control the crystal quality of perovskite in the preparation process, and ultimately improve or regulate the performance of perovskite materials and optoelectronic devices. Based on these two issues, when optimizing perovskite materials and optoelectronic devices, it is necessary to consider not to introduce new components to destroy the original perovskite components, and at the same time, it is also necessary to effectively match perovskite materials and charge transport materials. In the present invention, the polar interface is used as a means of regulating perovskite materials and optoelectronic devices, which can affect the performance of the final device through two aspects. The combination of materials makes each functional material play a role in ultimately regulating the performance of the device; on the other hand, it regulates the crystal growth process. By regulating the morphology of the perovskite, the density of defect states, etc., the luminescence performance, photovoltaic performance, current carrying performance, etc. can be improved or regulated. The purpose of sub-injection and carrier transport is to ultimately optimize or regulate the overall performance of the device.

For example, strong polar materials are used as interface materials of perovskite devices. Since perovskites are strong polar materials, perovskites can cooperate well with polar materials, so some different polar materials are selected as interface materials to introduce Lattice matching between charge transport materials and perovskite materials. By depositing ultrathin polar materials on polymer hole transport materials, the perovskite can be effectively grown on the polymer charge transport materials covered with polar interfaces, and the use of strong polar materials can increase the perovskite The quality of crystal growth is manifested in increasing the carrier lifetime of the perovskite film, increasing the external quantum efficiency PLQE of the perovskite film, and thus increasing the film stability and perovskite-based device performance.

The polar interface is deposited on the perovskite or charge transport material by physical or chemical methods such as thermal evaporation, magnetron sputtering, MOCVD, ALD, spraying, printing, chemical synthesis, and the typical deposition thickness ranges from 0.1 nm to 1000 nm. , for most of the current functional materials are nanoscale devices, which can meet the functional requirements of most of the current optoelectronic devices. Compared with the perovskite film deposited directly on the _SiO2 substrate, there are many defects and poor crystal orientation, and the polar interface plays a role in regulating the crystal growth. The matching of the polar interface with the polar perovskite can increase the film quality. It can increase the growth size of crystalline perovskite, reduce the density of surface defects and bulk defects, and will not affect the spectral characteristics and components of the film itself, so that the perovskite film can effectively inhibit non-radiative recombination, increase radiative recombination, and then increase the film loading. The lifetime of the carrier fluorescence is higher, and the higher photo-induced external quantum efficiency is achieved. The polar interface can reduce the fluorescence quenching of the perovskite film by the substrate or the transport material due to the isolation of the charge transport material and the perovskite material.

The polar interface can effectively match the perovskite material and the charge transport material. In optoelectronic devices prepared based on the polar interface, the interface can regulate the injection barrier between the charge transport material and the perovskite material, and regulate or increase the charge transport capability. As a very thin tunneling material, the polar interface will not restrict the flow of carriers in either PN-type or PIN-type materials. If a thicker polar interface material is used, its bipolar properties can be used to partially block holes or electrons to achieve charge balance in the device, and to achieve charge transfer regulation to balance the electron-hole transport rate, which can improve perovskite. The performance of optoelectronic devices, such as reducing the turn _- on voltage VT of light-emitting diodes, increasing the fill factor FF of solar cells, short-circuit current J _SC , open-circuit voltage V _OC , power conversion efficiency PCE , increasing the detection sensitivity of photodetectors and other parameters.

According to one aspect of the present invention, a method for optimizing perovskite films and light-emitting devices based on polar interfaces is proposed. Taking light-emitting films and light-emitting diodes as examples, the introduction of polar interfaces into substrates or charge transport materials and calcium The method between the titanite materials, and the performance of the perovskite thin film and the perovskite device can be regulated or optimized after the introduction of the polar interface through the test instrument.

1. Polar interfaces can tune or optimize the working principle of perovskite thin films

Perovskites are polar ionic crystals and can generally be synthesized by solution methods, thermal deposition methods, etc. In perovskite-based light-emitting films or optoelectronic devices, perovskites are composed of many nm or μm-sized perovskite blocks. Dense films are formed, and these blocks are formed by crystallization of many nm-sized perovskite crystals. In the process of perovskite forming crystalline blocks from raw materials, the external environment will have a great influence on the crystallization. When perovskite is combined with substrate and charge transport material, if there is a phenomenon of lattice mismatch, it will bring many problems. The main reasons are two aspects. On the one hand, the outstanding performance of substrates, charge transport materials and perovskite materials cannot be perfectly matched, which limits the performance of the prepared perovskite optoelectronic devices. For example, for optoelectronic devices prepared by solution methods, the charge Transport materials and perovskite materials have interfacial dissolution phenomenon, which leads to imperfect interface and affects the performance of various functional materials; on the other hand, perovskite materials have problems, which are manifested in poor crystal growth quality, many grain boundaries and interface defects Ultimately limit the performance of perovskite materials and optoelectronic devices.

In the present invention, the polar material is used as the interface material of the perovskite thin film and the optoelectronic device, and the main reason is to regulate or optimize the performance of the perovskite thin film or optoelectronic device through the polar interface. The main structural formula of the perovskite is ABX ₃ , where A is an organic or inorganic cation, B is a metal cation, and X is a halide anion. The combination of different materials A, B, and X leads to perovskite crystals that are also polar materials. According to the similar compatibility principle, perovskites can cooperate well with polar materials. The difference in the electronegativity of elements contained in different materials in nature will lead to the formation of materials with different polarities. In chemistry, polarity refers to a covalent bond or a covalent molecule due to the inhomogeneity of charge distribution. The resulting positive and negative charge centers do not coincide. If the charge distribution is uneven, the bond or molecule appears polar; if the charge distribution is very even, the bond or molecule appears nonpolar. Some physical properties of substances (such as solubility, melting point, etc.) are related to the polarity of the molecule. For polar covalent molecules, it means that the internal charge distribution is not uniform or the positive and negative charge centers do not overlap. The polarity of the molecule depends on the polarity of each bond in the molecule and their arrangement, and the polarity will affect the adjacent ones. The movement of the positive and negative charge centers of a material.

The difference in polarity of materials affects the surface energy of the material, which is a measure of the breakdown of chemical bonds between molecules when the surface of a substance is formed. In the theory of solid state physics, atoms on the surface have more energy than atoms inside the material, so according to the principle of minimum energy, atoms will spontaneously tend to the inside of the material rather than the surface. Another definition of surface energy is the excess energy on the surface of a material relative to the interior of the material. Breaking a solid material into smaller pieces requires breaking the chemical bonds within it, so it takes energy. If this decomposition process is reversible, then the energy required to decompose the material into small pieces is equal to the energy added to the surface of the small pieces of material, that is, the surface energy increases. But in fact, only surfaces that have just formed in a vacuum obey the law of conservation of energy. Because the newly formed surfaces are very unstable, they reduce the surface energy through the reorganization of surface atoms and their reactions with each other, or the adsorption of other molecules or atoms around them. For materials, since the bond energy of the surface layer atoms toward the outside is not compensated, the surface particles have additional potential energy than the internal particles, and the internal energy changes due to the change of the surface area of the object, the value of the surface energy per unit area is the same as the surface tension , but the two have different physical meanings, but the surface energy can be indirectly studied through surface tension.

Due to the low surface energy of some substrates and charge transport materials, the non-polar organic groups existing on the surface of some charge transport materials will also reduce the surface energy, which is not conducive to the spreading of perovskite materials, resulting in the growth of perovskite materials. It is not dense, the coverage is low, and the density of surface defects and bulk defects is high, which leads to a decrease in the molecular adsorption force, which will eventually lead to the phenomenon that the perovskite material is easy to fall off, bloom, and partially uncovered. In these, by introducing polar interfaces on the surface of substrates and charge transport materials with low surface energy, it can play a role in modifying the surfaces of substrates and charge transport materials, and at the same time, it can be properly matched with perovskite materials, which can reduce calcium The contact angle of the perovskite material on these substrates and charge transport materials further increases the wettability of the perovskite material on the surfaces of these substrates and charge transport materials, making the perovskite material more closely combined with the substrate and the charge transport material. It is firm and not easy to peel off, which makes the perovskite material grow denser, increase the coverage, and reduce the density of surface defects and bulk defects.

Through the interface materials of different polarities, the density, surface coverage, surface defect and bulk defect density of perovskite growth can be regulated. At the same time, the perovskite on the polar interface can be effectively grown to polymers with poor wettability. on charge transport materials. The use of a strongly polar interface material can induce the growth direction of the perovskite material, thereby increasing the directionality and density of the perovskite crystal material growth, which is manifested as increasing the carrier lifetime of the perovskite film and increasing the perovskite film. The external quantum efficiency PLQE, which in turn increases the stability of perovskite films and the performance of perovskite-based optoelectronic devices.

The polar interface is deposited on the perovskite or charge transport material by physical or chemical methods such as thermal evaporation, magnetron sputtering, MOCVD, ALD, spraying, printing, chemical synthesis, and the typical deposition thickness ranges from 0.1 nm to 1000 nm. , for most of the current functional materials are nanoscale devices, which can meet the functional requirements of most of the current optoelectronic devices. Compared with the perovskite film deposited directly on the _SiO2 substrate, there are many defects and poor crystal orientation, and the polar interface plays a role in regulating the crystal growth. The matching of the polar interface with the polar perovskite can increase the film quality. It can increase the growth size of crystalline perovskite, reduce the density of surface defects and bulk defects, and will not affect the spectral characteristics and components of the film itself, so that the perovskite film can effectively inhibit non-radiative recombination, increase radiative recombination, and then increase the film loading. The lifetime of the carrier fluorescence is higher, and the higher photo-induced external quantum efficiency is achieved. The polar interface can reduce the fluorescence quenching of the perovskite film by the substrate or the transport material due to the isolation of the charge transport material and the perovskite material.

The polar interface can effectively match the perovskite material and the charge transport material. In optoelectronic devices prepared based on the polar interface, the interface can regulate the injection barrier between the charge transport material and the perovskite material, and regulate or increase the charge transport capability. As a very thin tunneling material, the polar interface will not restrict the flow of carriers in either PN-type or PIN-type materials. If a thicker polar interface material is used, its bipolar properties can be used to partially block holes or electrons to achieve charge balance in the device, and to achieve charge transfer regulation to balance the electron-hole transport rate, which can improve perovskite. The performance of optoelectronic devices, such as reducing the turn _- on voltage VT of light-emitting diodes, increasing the fill factor FF of solar cells, short-circuit current J _SC , open-circuit voltage V _OC , power conversion efficiency PCE , increasing the detection sensitivity of photodetectors and other parameters.

2. Preparation method and characterization of hydrophilicity experiment after introducing polar interface

Figure 3 shows the flow chart of the hydrophilic experimental preparation of the polar interface. The polar interface is deposited on a quartz piece without conductive glass ITO. The size of the quartz piece is 12mm*12mm. The quartz piece is sonicated for 15 minutes with deionized water, acetone, isopropanol, deionized water, and isopropanol before use. cleaning. The cleaned quartz wafer was placed in a UV-Ozone ozone cleaning machine for 15 minutes of ozone cleaning, and then the quartz wafer was transferred to a glove box filled with high-purity nitrogen, and the polar interface material to be evaporated was selected, and then transferred The polar interface evaporation is carried out in a vacuum coating machine until the evaporation is completed. The pressure of vacuum evaporation was 5 x 10 ^-4 Pa, the evaporation rate was measured by quartz crystal, the evaporation rate was 0.01 nm/s, and the thickness of LiF evaporation at the polar interface was 1 nm.

Figure 4 shows the comparison of the hydrophilic wetting experiments before and after adding the interface. The test solution used is DMSO. It can be seen that the wettability of the substrate after adding the interface is enhanced, indicating that after adding the interface, the solvent is easier Spread out, and the perovskite is dissolved in the DMSO solvent, so the perovskite will be more closely combined with the substrate at the polar interface.

3. Comparative characterization of charge transport materials with polar interface and plasma surface treatments, respectively

Figure 5 is a flow chart of surface treatment using polar interface and plasma, respectively. Due to the relatively low surface energy of the selected charge transport material, the name of the charge transport material is poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) (abbreviated as TFB). The perovskite material is not easy to spread, resulting in incomplete film coverage. Generally, plasma surface treatment is used to increase the surface energy, making the perovskite coating more complete. The charge transport material TFB is prepared on quartz glass, the size of the quartz glass is 12mm*12mm, and the quartz glass is sonicated for 15 minutes with 5 steps of deionized water, acetone, isopropanol, deionized water, and isopropanol before use. cleaning. The cleaned quartz glass was placed in a UV-Ozone ozone cleaning machine for 15 minutes of ozone cleaning, then the quartz glass was transferred to a glove box filled with high-purity nitrogen, and the quartz glass was placed on a vacuum spin coater for spin coating of charge transport materials. The charge transport material TFB is dissolved in chlorobenzene solution (CB for short) with a concentration of 6mg/ml. When coating the charge transport material TFB, use a pipette with a range of 100uL to draw 30uL of charge transport solution and coat it on the ITO conductive glass , turn on the vacuum spin coater and spin at 3000 rpm/s for 60 s, and place the ITO conductive glass with the charge transport material after spin coating on a hot stage for annealing at 120 °C for 10 min to obtain a flat charge transport material TFB film with a thickness of 10 nm. .

The quartz glass covered with charge transport material was then transferred into a vacuum coater for polar interfacial LiF evaporation. The pressure of vacuum evaporation was 5 x 10 ^-4 Pa, the evaporation rate was measured by a quartz crystal oscillator, the evaporation rate was 0.01 nm/s, and the thickness of LiF evaporation at the polar interface was 1 nm until the evaporation was completed.

The charge transport material substrate used as a comparative experiment was directly treated with a plasma cleaner for 5 s.

Figure 6 shows the SEM image of the surface morphology of the charge transport material treated with LiF polar interface and plasma. Because TFB and its derivatives are used as hole transport materials with outstanding transport properties, but calcium ion using DMSO as a solvent Titanium is not compatible with TFB, and perovskite cannot be directly deposited on functional materials based on TFB and its derivatives. The general practice is to use Plasma plasma surface cleaner and UV-Ozone surface cleaner for surface treatment, but after surface treatment It will destroy the surface morphology and form more holes, which will increase the injection barrier or form surface defects or bulk defects at the interface when in contact with the perovskite, resulting in the degradation of device performance. The TFB hole transport material treated with LiF interface is more dense, which reduces the possibility of device leakage without changing the performance of the charge transport material. At the same time, the polar interface represented by LiF acts as a tunneling layer, which will reduce the charge injection barrier, so that the charge transport material with excellent performance and perovskite material can be friendly matched, and the overall performance of the device can be improved.

4. SEM test comparison and characterization of perovskite on interfaces of different polarities

Figure 7 shows the SEM flow chart of the spin-coated perovskite luminescent film. The luminescent film is deposited on a quartz sheet without conductive glass ITO, the size of the quartz sheet is 12mm*12mm, and the quartz sheet is treated with deionized water, acetone, isopropanol, deionized water, isopropanol, deionized water, isopropanol before use. The propanol step was sonicated for 15 min. The cleaned quartz wafer was placed in a UV-Ozone ozone cleaning machine for 15 minutes of ozone cleaning, and then the quartz wafer was transferred to a glove box filled with high-purity nitrogen, and the polar interface material to be evaporated was selected, and then transferred In the vacuum coating machine, the polar interface evaporation experiments were carried out, and the polar interface materials were LiF, CaF ₂ , NaF, CsF, and MgO. As a comparison, the quartz glass SiO ₂ was not subjected to evaporation experiments. The pressure of vacuum evaporation is 5 x 10 ^-4 Pa, the evaporation rate is measured by a quartz crystal oscillator, the evaporation rate is 0.01 nm/s, and the evaporation thickness of the polar interface is 1 nm. The sheets were then transferred to a glove box filled with high-purity nitrogen to spin-coat the perovskite material.

The perovskite precursor solution is PEA _{n CsPbn} Br _3n+1 , which consists of 110 mg of lead bromide (PbBr ₂ ), 64 mg of cesium bromide (CsBr) and 24 mg of 2-phenethylammonium bromide (PEABr) Dissolved in 1 mL of dimethyl sulfoxide (DMSO) solution, the concentration of the solution was 0.3 mol/L, and the solution was placed on a hot stage at 60 °C and stirred for 1 h. When spin coating, put the quartz sheet on the vacuum spin coater, apply the prepared precursor perovskite solution to the quartz sheet with polar interface, spin at 3000 rpm/s for 60 s, and complete the spin coating. The quartz glass of titanium ore material was placed on a hot stage for annealing at 60 °C for 10 min, and a flat perovskite material film with a thickness of 35 nm was obtained.

Figure ₈ shows the SEM morphologies of perovskite films formed on different interfaces. The substrate used is quartz sheet SiO ₂ . The ability to form dense films means that devices based on polar interfaces will have a good interface and reduce the probability of leakage. Perovskite deposited on quartz sheet SiO ₂ and weakly polar interface MgO has more holes, The leakage phenomenon will be caused in the formed device, so the strong polar interface can play a role in regulating the growth of perovskite, inducing the process of perovskite crystallization, and then changing the morphology of perovskite growth.

5. Wavelength test comparison and characterization of perovskite on interfaces of different polarities

Figure 9 is a flow chart of the Wavelength test of spin-coated perovskite luminescent thin films. The luminescent film is deposited on a quartz sheet without conductive glass ITO, the size of the quartz sheet is 12mm*12mm, and the quartz sheet is treated with deionized water, acetone, isopropanol, deionized water, isopropanol, deionized water, isopropanol before use. The propanol step was sonicated for 15 min. The cleaned quartz wafer was placed in a UV-Ozone ozone cleaning machine for 15 minutes of ozone cleaning, and then the quartz wafer was transferred to a glove box filled with high-purity nitrogen, and the polar interface material to be evaporated was selected, and then transferred Go to the vacuum coating machine to carry out the evaporation experiments of polar interfaces respectively. The polar interface materials are Cs ₂ CO ₃ , LiF, CaF ₂ , NaF, KF, CsF, respectively. As a comparison, the quartz glass SiO ₂ (named as None) is not. Evaporation experiments were carried out. The pressure of vacuum evaporation is 5 x 10 ^-4 Pa, the evaporation rate is measured by a quartz crystal oscillator, the evaporation rate is 0.01 nm/s, and the evaporation thickness of the polar interface is 1 nm. The sheets were then transferred to a glove box filled with high-purity nitrogen to spin-coat the perovskite material.

The perovskite precursor solution is PEA _{n CsPbn} Br _3n+1 , which consists of 110 mg of lead bromide (PbBr ₂ ), 64 mg of cesium bromide (CsBr) and 24 mg of 2-phenethylammonium bromide (PEABr) Dissolved in 1 mL of dimethyl sulfoxide (DMSO) solution, the concentration of the solution was 0.3 mol/L, and the solution was placed on a hot stage at 60 °C and stirred for 1 h. When spin coating, put the quartz sheet on the vacuum spin coater, apply the prepared precursor perovskite solution to the quartz sheet with polar interface, spin at 3000 rpm/s for 60 s, and complete the spin coating. The quartz glass of titanium ore material was placed on a hot stage for annealing at 60 °C for 10 min, and a flat perovskite material film with a thickness of 35 nm was obtained.

The spectral measurement of the luminescent film is realized by a luminance meter. The perovskite-deposited quartz sheet is placed on the luminance meter test bench, and the fluorescent film is excited by 365 nm ultraviolet light. Complete coverage of the sample luminescence range.

Figure 10 shows the PL spectra of materials grown on interfaces of different polarities. The spectral measuring instrument is a luminance meter, the horizontal axis is the wavelength Wavelength, in nm, and the vertical axis is the normalized spectral intensity Normalized PL. The luminescence spectrum of the perovskite in Figure 5 is basically unchanged, indicating that the polar interface does not change the crystalline composition of the perovskite.

6. Absorbance test steps and characterization of perovskite on interfaces of different polarities

Figure 11 is the flow chart of the Absorbance test of the spin-coated perovskite luminescent film. The luminescent film is deposited on a quartz sheet without conductive glass ITO, the size of the quartz sheet is 12mm*12mm, and the quartz sheet is treated with deionized water, acetone, isopropanol, deionized water, isopropanol, deionized water, isopropanol before use. The propanol step was sonicated for 15 min. The cleaned quartz wafer was placed in a UV-Ozone ozone cleaning machine for 15 minutes of ozone cleaning, and then the quartz wafer was transferred to a glove box filled with high-purity nitrogen, and the polar interface material to be evaporated was selected, and then transferred The polar interface was vapor-deposited in a vacuum coating machine, and the polar interface materials were LiF, CaF ₂ , NaF, KF, and CsF, which were used as the quartz glass SiO ₂ non-polar interface material for the comparative test. The pressure of vacuum evaporation is 5 x 10 ^-4 Pa, the evaporation rate is measured by a quartz crystal oscillator, the evaporation rate is 0.01 nm/s, and the evaporation thickness of the polar interface is 1 nm. The sheets were then transferred to a glove box filled with high-purity nitrogen to spin-coat the perovskite material.

The perovskite precursor solution is PEA _{n CsPbn} Br _3n+1 , which consists of 110 mg of lead bromide (PbBr ₂ ), 64 mg of cesium bromide (CsBr) and 24 mg of 2-phenethylammonium bromide (PEABr) Dissolved in 1 mL of dimethyl sulfoxide (DMSO) solution, the concentration of the solution was 0.3 mol/L, and the solution was placed on a hot stage at 60 °C and stirred for 1 h. When spin coating, put the quartz sheet on the vacuum spin coater, apply the prepared precursor perovskite solution to the quartz sheet with polar interface, spin at 3000 rpm/s for 60 s, and complete the spin coating. The quartz glass of titanium ore material was placed on a hot stage for annealing at 60 °C for 10 min, and a flat perovskite material film with a thickness of 35 nm was obtained.

The absorption measurement of the thin film is realized by a UV-visible spectrophotometer. The perovskite-deposited quartz sheet is placed on the test bench of the spectrophotometer. The excitation spectrum ranges from 190 nm to 1100 nm, which can completely cover the emission range of the sample. Place the quartz plate covered with perovskite on the UV spectrophotometer test stand, and use the standard quartz plate to perform one-step spectral calibration before testing to obtain a more accurate measurement. The UV spectrophotometer can completely cover the light absorption range of the sample.

Figure 12 shows the absorption spectra of perovskite materials grown on interfaces of different polarities. From top to bottom, the polar interface materials are LiF, CaF ₂ , NaF, KF, CsF and SiO ₂ , among which LiF, CaF ₂ , _NaF , KF, CsF denote perovskite deposition onto substrates covered with corresponding polar interface materials, and SiO denotes perovskite deposition onto quartz substrates covered with non-polar interface materials. The absorption spectrum measuring instrument is an ultraviolet spectrophotometer, the horizontal axis is the wavelength of the spectrum emitted by the ultraviolet spectrophotometer, the unit is nm, and the vertical axis is the absorption coefficient Absorbance of the material detected by the ultraviolet spectrophotometer corresponding to the current wavelength. It can be seen from Figure 6 that the absorption spectrum of the perovskite material has almost no change, indicating that the added polar interface does not change the essential structure and composition of the light-emitting film.

7. X-ray diffraction preparation and characterization (XRD) of perovskite on interfaces of different polarities

FIG. 13 is the XRD flow chart of the spin-coated perovskite luminescent thin film test. The luminescent film is deposited on a quartz sheet without conductive glass ITO, the size of the quartz sheet is 12mm*12mm, and the quartz sheet is treated with deionized water, acetone, isopropanol, deionized water, isopropanol, deionized water, isopropanol before use. The propanol step was sonicated for 15 min. The cleaned quartz wafer was placed in a UV-Ozone ozone cleaning machine for 15 minutes of ozone cleaning, and then the quartz wafer was transferred to a glove box filled with high-purity nitrogen, and the polar interface material to be evaporated was selected, and then transferred Go to the vacuum coating machine to carry out the evaporation experiment of polar interface respectively. The polar interface materials are MoO ₃ , ZnO, MgO, Li ₂ CO ₃ , Na ₂ CO ₃ , Cs ₂ CO ₃ , LiF, CaF ₂ , NaF, KF , CsF. The pressure of vacuum evaporation was 5 x 10 ^-4 Pa, the evaporation rate was measured by a quartz crystal oscillator, the evaporation rate was 0.01 nm/s, the thickness of the polar interface evaporation was 1 nm, and the quartz plate with the polar interface was evaporated. Then transfer to a glove box filled with high-purity nitrogen to spin-coat the perovskite material.

The perovskite precursor solution is PEA _{n CsPbn} Br _3n+1 , which consists of 110 mg of lead bromide (PbBr ₂ ), 64 mg of cesium bromide (CsBr) and 24 mg of 2-phenethylammonium bromide (PEABr) Dissolved in 1 mL of dimethyl sulfoxide (DMSO) solution, the concentration of the solution was 0.3 mol/L, and the solution was placed on a hot stage at 60 °C and stirred for 1 h. When spin coating, put the quartz sheet on the vacuum spin coater, apply the prepared precursor perovskite solution to the quartz sheet with polar interface, spin at 3000 rpm/s for 60 s, and complete the spin coating. The quartz glass of titanium ore material was placed on a hot stage for annealing at 60 °C for 10 min, and a flat perovskite material film with a thickness of 35 nm was obtained.

The XRD diffraction measurement adopts Bruker equipment, the measurement degree range is 10°-45°, the measurement step interval is 0.02°, the measurement time is 5°/min, the measurement voltage is 40kV, and the measurement current is 30mA.

Figure 14 shows the thin film XRD of perovskite on different interfaces, the horizontal axis is degrees, and the vertical axis is relative intensity. The polar interface materials from top to bottom are LiF, CaF ₂ , NaF, KF, CsF, SiO ₂ and bkgd, respectively, where LiF, CaF ₂ , NaF, KF, CsF represent the perovskite deposited on the surface covered with the corresponding polar interface materials On the substrate of , _SiO2 represents the perovskite deposited on the quartz substrate covered with non-polar interface material, and bkgd represents the diffraction peak of the quartz substrate without perovskite covering. Compared with the perovskite film deposited directly on the quartz sheet _SiO2 substrate, both the 100 and 200 peaks tend to be enhanced, but the appearance of other peak types is not increased, indicating that the polar interface enhances the perovskite in these The composition of the peak plays a role in regulating the composition in the perovskite film.

8. Photoinduced external quantum efficiency PLQE and characterization of perovskite at different polar interfaces

Figure 15 is a flow chart of the photo-induced quantum efficiency PLQE test at different interfaces. The luminescent film is deposited on a quartz sheet without conductive glass ITO, the size of the quartz sheet is 12mm*12mm, and the quartz sheet is treated with deionized water, acetone, isopropanol, deionized water, isopropanol, deionized water, isopropanol before use. The propanol step was sonicated for 15 min. The cleaned quartz wafer was placed in a UV-Ozone ozone cleaning machine for 15 minutes of ozone cleaning, and then the quartz wafer was transferred to a glove box filled with high-purity nitrogen, and the polar interface material to be evaporated was selected, and then transferred Go to the vacuum coating machine to carry out the evaporation experiment of polar interface respectively. The polar interface materials are MoO ₃ , ZnO, MgO, Li ₂ CO ₃ , Na ₂ CO ₃ , Cs ₂ CO ₃ , LiF, CaF ₂ , NaF, KF , CsF. The pressure of vacuum evaporation is 5 x 10 ^-4 Pa, the evaporation rate is measured by a quartz crystal oscillator, the evaporation rate is 0.01 nm/s, and the evaporation thickness of the polar interface is 1 nm. The sheets were then transferred to a glove box filled with high-purity nitrogen to spin-coat the perovskite material.

The perovskite precursor solution is PEA _{n CsPbn} Br _3n+1 , which consists of 110 mg of lead bromide (PbBr ₂ ), 64 mg of cesium bromide (CsBr) and 24 mg of 2-phenethylammonium bromide (PEABr) Dissolved in 1 mL of dimethyl sulfoxide (DMSO) solution, the concentration of the solution was 0.3 mol/L, and the solution was placed on a hot stage at 60 °C and stirred for 1 h. When spin coating, put the quartz sheet on the vacuum spin coater, apply the prepared precursor perovskite solution to the quartz sheet with polar interface, spin at 3000 rpm/s for 60 s, and complete the spin coating. The quartz glass of titanium ore material was placed on a hot stage for annealing at 60 °C for 10 min, and a flat perovskite material film with a thickness of 35 nm was obtained.

Take the perovskite-coated quartz sheet out of the glove box to measure the photo-induced quantum efficiency PLQE, and place it on an external integrating sphere for PLQE measurement. The integrating sphere system is composed of Ocean HDX series spectrometer, 405 nm wavelength continuous laser, and 10 cm diameter integrating sphere. 2. It is composed of a computer host computer system, and a three-step method is used to measure the PLQE of perovskite samples.

Figure 16 shows the photoinduced external quantum efficiency PLQE of perovskite as a function of the electronegativity of different polar interfaces, the horizontal axis is the difference in electronegativity of the polar interface, and the vertical axis is the polar interface Photoinduced external quantum efficiency PLQE at the interface. where the _SiO2 interface is perovskite deposited directly onto the quartz substrate. Among them, on the polar interface NiO, MoO ₃ , ZnO, MgO, Li ₂ CO ₃ , Na ₂ CO ₃ will reduce the PLQE of perovskite, indicating that there is a process of fluorescence quenching or light absorption, which affects the perovskite. PLQE, the polar interface has less and less influence on perovskite as the polarity increases, indicating that polarity matching is required when utilizing polar interfaces in perovskite systems. Among them, the fluorescence of perovskite will increase on the polar interface Cs ₂ CO ₃ , LiF, CaF ₂ , NaF, KF and CsF. Compared with the SiO ₂ material interface, the polar interface inhibits the non-radiative recombination and increases the radiation. The composite shows that the strong polar interface can enable the perovskite film to achieve higher light extraction efficiency, and at the same time, with the change of metal activity, it shows a phenomenon of decreasing in turn, indicating that the performance of perovskite decreases when growing on the surface of different metal compounds. After the introduction of several interfaces, the fluorescence lifetime of several interfaces that can enhance PLQE will also increase, indicating that the interface effect makes the perovskite growth quality better, suppresses the non-radiative recombination process, and enhances the radiative recombination process. higher PLQE.

9. Preparation method and test characterization of fluorescence lifetime test of perovskite on different interfaces

Figure 17 shows the preparation steps of perovskite on different charge transport materials. The fluorescence lifetime test of the luminescent film on different interfaces is based on three structures: quartz substrate, charge transport layer PVK, and charge transport layer TFB/LiF. The size of the quartz sheet is 12mm*12mm. The steps of acetone, isopropanol, deionized water, isopropanol, deionized water, and isopropanol were ultrasonically cleaned for 15 minutes. The cleaned quartz wafers were placed in a UV-Ozone ozone cleaning machine for 15 minutes of ozone cleaning.

The perovskite precursor solution is PEA _{n CsPbn} Br _3n+1 , which consists of 110 mg of lead bromide (PbBr ₂ ), 64 mg of cesium bromide (CsBr) and 24 mg of 2-phenethylammonium bromide (PEABr) Dissolved in 1 mL of dimethyl sulfoxide (DMSO) solution, the concentration of the solution was 0.3 mol/L, and the solution was placed on a hot stage at 60 °C and stirred for 1 h.

① For perovskite samples without charge transport layer and interface, the perovskite solution is directly spin-coated.

②For samples with added charge transport layer PVK, it is necessary to spin-coat the charge transport material PVK first. The charge transport material PVK is dissolved in chlorobenzene solution (CB for short) at a concentration of 6mg/ml. When coating the charge transport material PVK, use A pipette with a range of 100uL draws 30uL of charge transport solution and coats it on the quartz glass. Turn on the vacuum spin coater and spin at 3000 rpm/s for 60 s. After the spin coating is completed, the quartz glass of the charge transport material is placed on a hot stage. After annealing at 120 ℃ for 10 min, a flat PVK film with a thickness of 10 nm was obtained. Then use a pipette with a range of 100uL to draw 30uL of perovskite solution and coat it on the quartz glass, turn on the vacuum spin coater and spin at 3000 rpm/s for 60 s, and place the quartz glass of the perovskite material after the spin coating is completed. Annealed at 60 °C for 10 min on a hot stage to obtain a flat perovskite material film with a thickness of 35 nm.

③ For the samples with the charge transport layer TFB/LiF added, the charge transport material TFB needs to be spin-coated first. The charge transport material TFB is dissolved in a chlorobenzene solution (CB for short) at a concentration of 6 mg/ml. When coating the charge transport material TFB , use a pipette with a range of 100uL to draw 30uL of charge transfer solution and coat it on the quartz glass, turn on the vacuum spin coater and spin at 3000 rpm/s for 60 s, and place the quartz glass of the charge transfer material after spin coating on the hot stage. Annealed at 120 °C for 10 min to obtain a flat charge transport material TFB film with a thickness of 10 nm.

Subsequently, the quartz sheets were transferred to a glove box filled with high-purity nitrogen, and then transferred to a vacuum coater for polar interfacial LiF evaporation. The pressure of vacuum evaporation was 5 x 10 ^-4 Pa, the evaporation rate was measured by a quartz crystal oscillator, the evaporation rate was 0.01 nm/s, the thickness of the polar interface evaporation was 1 nm, and the quartz plate with the polar interface was evaporated. Then transfer to a glove box filled with high-purity nitrogen to spin-coat the perovskite material.

Use a pipette with a range of 100uL to draw 30uL of perovskite solution onto the quartz glass, turn on the vacuum spin coater and spin at 3000 rpm/s for 60 s. After annealing at 60 °C for 10 min on the stage, a flat perovskite material film with a thickness of 35 nm was obtained.

The fluorescence lifetime measurement of the luminescent film is realized by the time-correlated single photon counter TCSPC. The prepared film sample quartz plate is placed in the fluorescence lifetime measurement sample test stand, and the sample is excited with a 405 nm pulsed laser with a frequency range of 20 kHz to 2 MHz. , the average power of the pulsed laser at 2MHz is 6mW, the luminescence measurement of the sample thin film is measured by a single photon counter probe, the probe is an avalanche photodiode APD, the power supply is +12 V, and the multiplication factor of the avalanche photodiode is not used to reduce the dark current of the detector For the introduced background noise signal, the optical-electrical signal output by the APD is amplified by the differential amplifier circuit, and the pulse shaping circuit and the pulse filter circuit are used for pulse shaping and pulse filtering, and then a T-type amplification is performed to extract the signal with high signal. The fluorescence-to-electrical signal of the noise ratio, the electric signal is input into the TCSPC host through the coaxial cable to read the fluorescence lifetime of the luminescent film sample.

Figure 18 shows the fluorescence lifetime of perovskite at different interfaces, the unit is ns, and the vertical axis is the current density at the corresponding voltage, the unit is mA cm ^-2 . The fluorescence lifetimes of PVK/perovskite, TFB/LiF/perovskite, and perovskite were compared, in which PVK and TFB were charge transport materials, LiF was polar interface, and perovskite was perovskite. Perovskite on quartz substrate and PVK substrate Ore has a close fluorescence lifetime, while perovskite on TFB/LiF has the longest fluorescence lifetime, indicating that LiF acts as a polar interface to induce perovskite crystallization, regulating the growth process of perovskite, which in turn reduces the density of defect states, thereby increasing the fluorescence lifetime.

10. Preparation method and test characterization of polar interface devices with different thicknesses

Figure 19 is a flow chart of the fabrication of interfaces with different thicknesses. The light-emitting diode is prepared on the ITO conductive glass, the size of the ITO conductive glass is 12mm*12mm, the ITO conductive glass is used with deionized water, acetone, isopropanol, deionized water, isopropanol, deionized water, isopropanol before use. 7 steps of propanol for 15 min ultrasonic cleaning. The cleaned ITO conductive glass was placed in a UV-Ozone ozone cleaning machine for 15 minutes of ozone cleaning, then the ITO conductive glass was transferred to a glove box filled with high-purity nitrogen, and the ITO conductive glass was placed on a vacuum spin coater for charge transfer material. Spin coating, the charge transport material name is poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) (abbreviated as TFB). TFB is dissolved in chlorobenzene solution (CB for short) with a concentration of 6mg/ml. When coating the charge transport material TFB, use a pipette with a range of 100uL to draw 30uL of charge transport solution onto the ITO conductive glass, and turn on the vacuum. The spin coating machine was used for spin coating at 3000 rpm/s for 60 s, and the ITO conductive glass with charge transport material after spin coating was placed on a hot stage for annealing at 120 °C for 10 min to obtain a flat TFB film of charge transport material.

The ITO conductive glass covered with charge transport material was then transferred into a vacuum coater for polar interfacial LiF evaporation. The pressure of vacuum evaporation is 5 x 10 ^-4 Pa, the evaporation rate is measured by a quartz crystal oscillator, the evaporation rate is 0.01nm/s, and the thickness of the polar interface LiF evaporation is 0nm, 1nm, 2nm, 5nm. After evaporation of polar interface LiF, the ITO conductive glass substrate was transferred to a glove box filled with high-purity nitrogen for spin coating of perovskite solution.

Put the spin-coated perovskite ITO conductive glass into a vacuum coating machine for charge transport material evaporation. The charge transport material is named 2,2', 2"-(1,3,5-benzimidazole)-three (1-Phenyl-1-H-benzimidazole) (abbreviated as TPBi), the pressure of vacuum evaporation is 5 x 10 ^-4 Pa, the evaporation rate is measured by a quartz crystal, and the evaporation rate is 0.1 nm/s , the thickness of TPBi is 40 nm.

After evaporating the charge transport material TPBi, replace the deposited metal mask. The mask can limit the luminous size to 5.25mm ² . The electrode materials are lithium fluoride, LiF and Al, and the evaporation rate is measured by a quartz crystal oscillator. , the lithium fluoride LiF evaporation rate is 0.01 nm/s, the thickness of LiF is 1 nm, and the thickness of metal aluminum Al evaporation is 100 nm.

The prepared device is tested by the OLED photochromic test system to test the external quantum efficiency EQE. The efficiency test of the light-emitting diode is realized by the OLED 2000 photochromic external quantum efficiency test system, which includes a luminance meter, a Keithley source meter 2400 , computer host computer, industrial control camera CCD, sample test bench, etc. The luminance meter is used to detect the spectrum and spectral power of light-emitting diodes. The 2400 leads the positive and negative terminals and then connects the positive and negative terminals of the light-emitting diode. The voltage applied to the light-emitting device ranges from 0 V to 8 V, and the voltage step interval is 0.1 V. The current through the light-emitting diode is measured by the four-wire method, and the current is detected. The range is 1nA ~ 100 mA, and the current density range is 10 ^-3 – 10 ³ mA/cm ² , so it can meet the current testing requirements of light-emitting diodes. The computer host computer realizes the function of interactive communication with the luminance meter, Keithley source meter 2400, and industrial control camera CCD, obtains the collected spectrum, spectral power, voltage, current and detection images, and realizes the real-time display function. The sample test bench is responsible for light-emitting diodes The sample is placed to achieve the three-dimensional position adjustment function, which makes the observation clearer and the measurement more accurate, so as to achieve the purpose of optimizing the performance test.

Figure 20 shows the effect of interfaces with different thicknesses on the charge injection capability. The horizontal axis is the voltage applied to both ends of the LED, in V, and the vertical axis is the current density at the corresponding voltage, in mAcm ^-2 . After adding LiF polar interface, the thickness of LiF is 0nm, 1nm, 2nm, 5nm, and its charge transport ability is greatly improved, and the current density increases rapidly after 2V, which shows that the slope of current density increases with voltage. , indicating that its charge injection ability has been enhanced, and the slope of the contrast current density curve with voltage is higher than that of the material without LiF, indicating that the ultra-thin LiF material can increase the effective charge injection. In addition, after changing the interface thickness, its charge transport ability and There is no change, indicating that the polar interface exists as a tunneling layer, and will not affect the charge injection and increase the potential barrier.

11. Preparation method and test characterization of polar interface for light-emitting devices

FIG. 21 is a flow chart of the fabrication of the light emitting diode device. The light-emitting diode is prepared on the ITO conductive glass, the size of the ITO conductive glass is 12mm*12mm, the ITO conductive glass is used with deionized water, acetone, isopropanol, deionized water, isopropanol, deionized water, isopropanol before use. 7 steps of propanol for 15 min ultrasonic cleaning. The cleaned ITO conductive glass was placed in a UV-Ozone ozone cleaning machine for 15 minutes of ozone cleaning, then the ITO conductive glass was transferred to a glove box filled with high-purity nitrogen, and the ITO conductive glass was placed on a vacuum spin coater for charge transfer material. Spin coating, the charge transport material name is poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) (abbreviated as TFB). TFB is dissolved in chlorobenzene solution (CB for short) with a concentration of 6mg/ml. When coating the charge transport material TFB, use a pipette with a range of 100uL to draw 30uL of charge transport solution onto the ITO conductive glass, and turn on the vacuum. The spin coating machine was used for spin coating at 3000 rpm/s for 60 s, and the ITO conductive glass with charge transport material after spin coating was placed on a hot stage for annealing at 120 °C for 10 min to obtain a flat TFB film of charge transport material.

The ITO conductive glass covered with charge transport material was then transferred into a vacuum coater for polar interfacial LiF evaporation. The pressure of vacuum evaporation was 5 x 10 ^-4 Pa, the evaporation rate was measured by a quartz crystal oscillator, the evaporation rate was 0.01 nm/s, and the thickness of LiF evaporation at the polar interface was 1 nm. After evaporation of polar interface LiF, the ITO conductive glass substrate was transferred to a glove box filled with high-purity nitrogen for spin coating of perovskite solution.

The perovskite precursor solution is PEA _{n CsPbn} Br _3n+1 , which consists of 110 mg of lead bromide (PbBr ₂ ), 64 mg of cesium bromide (CsBr) and 24 mg of 2-phenethylammonium bromide (PEABr) Dissolved in 1 mL of dimethyl sulfoxide (DMSO) solution, the concentration of the solution was 0.3 mol/L, and the solution was placed on a hot stage at 60 °C and stirred for 1 h. When spin coating, put the ITO conductive glass on the vacuum spin coater, draw 30uL of solution with a measuring range of 100uL and coat it on the ITO conductive glass evaporated with polar interface and charge transport material, turn on the vacuum spin coater button at 3000 rpm/s Spin-coating for 60 s at a rotational speed and annealing at 60 °C for 10 min can obtain a flat perovskite film.

Put the spin-coated perovskite ITO conductive glass into a vacuum coating machine for charge transport material evaporation. The charge transport material is named 2,2', 2"-(1,3,5-benzimidazole)-three (1-Phenyl-1-H-benzimidazole) (abbreviated as TPBi), the pressure of vacuum evaporation is 5 x 10 ^-4 Pa, the evaporation rate is measured by a quartz crystal, and the evaporation rate is 0.1 nm/s , the thickness of TPBi is 40 nm.

After evaporating the charge transport material TPBi, replace the deposited metal mask. The mask can limit the luminous size to 5.25mm ² . The electrode materials are lithium fluoride, LiF and Al, and the evaporation rate is measured by a quartz crystal oscillator. , the lithium fluoride LiF evaporation rate is 0.01 nm/s, the thickness of LiF is 1 nm, and the thickness of metal aluminum Al evaporation is 100 nm.

The prepared device is tested by the OLED photochromic test system to test the external quantum efficiency EQE. The efficiency test of the light-emitting diode is realized by the OLED 2000 photochromic external quantum efficiency test system, which includes a luminance meter, a Keithley source meter 2400 , computer host computer, industrial control camera CCD, sample test bench, etc. The luminance meter is used to detect the spectrum and spectral power of light-emitting diodes. The 2400 leads the positive and negative terminals and then connects the positive and negative terminals of the light-emitting diode. The voltage applied to the light-emitting device ranges from 0 V to 8 V, and the voltage step interval is 0.1 V. The current through the light-emitting diode is measured by the four-wire method, and the current is detected. The range is 1nA ~ 100 mA, and the current density range is 10 ^-3 – 10 ³ mA/cm ² , so it can meet the current testing requirements of light-emitting diodes. The computer host computer realizes the function of interactive communication with the luminance meter, Keithley source meter 2400, and industrial control camera CCD, obtains the collected spectrum, spectral power, voltage, current and detection images, and realizes the real-time display function. The sample test bench is responsible for light-emitting diodes The sample is placed to achieve the three-dimensional position adjustment function, which makes the observation clearer and the measurement more accurate, so as to achieve the purpose of optimizing the performance test.

Figure 22 shows the device efficiencies based on polar interface transport materials and other transport materials. The horizontal axis is the current density through the light-emitting diode, in mA cm ^-2 , and the vertical axis is the external quantum efficiency, EQE, in %. The structure of the light-emitting diode is ITO/HTL/Perovskite/TPBi/LiF/Al, in which HTL is a hole transport material, which are TFB/LiF and PVK respectively. It can be seen from the curve that the hole mobility of TFB is higher than that of PVK. High, higher hole mobility increases the charge transport capability at low voltages. Deposition of LiF on TFB with polar interface has the highest efficiency, indicating that replacing PVK with LiF enables better charge injection into the perovskite functional material and reduces the barrier of the transport material interface and the perovskite material.

Claims (8)

1. A halide perovskite optoelectronic device based on a polar interface, characterized in that: the preparation process of the perovskite luminescent thin film luminescent device comprises the following steps:

preparation of the substrate: firstly, respectively carrying out ultrasonic cleaning for 15 minutes by using seven steps of deionized water, acetone, isopropanol, deionized water and isopropanol, then putting the substrate into a UV-Ozone cleaning machine for carrying out Ozone cleaning for 15 minutes, then transferring the substrate into a vacuum coating machine for carrying out polar interface evaporation, wherein the evaporation process in the vacuum coating machine is finished in a glove box, and obtaining the substrate with the polar interface after evaporation;

and transferring the substrate with the evaporated polar interface to a glove box filled with high-purity nitrogen to spin-coat the perovskite thin film: when the perovskite is coated in a spin mode, the substrate coated with the polar interface in a vapor deposition mode is placed on a vacuum spin coating machine, the perovskite precursor solution absorbed by a liquid transfer gun is dripped onto the substrate coated with the polar interface in a vapor deposition mode, the vacuum spin coating machine carries out spin coating for 60s at the rotating speed of 3000 rpm/s, then the substrate coated with the perovskite in a spin mode is placed on a hot bench to be annealed for 10min at the temperature of 60 ℃, and the perovskite luminescent thin film luminescent device is obtained.

2. The polar interface based halide perovskite optoelectronic device of claim 1, wherein: the polar interface material is composed of a plurality of compounds, including polar interface materials capable of forming compounds during different periods, polar interface materials capable of forming compounds among different groups, strong polar interface materials capable of forming compounds among different groups, and other interface materials matched with perovskite materials.

3. A polar interface based halide perovskite optoelectronic device as claimed in claim 2 wherein: polar interface materials that can form compounds during different cycles include metal oxide material interface ZrO₂、V₂O₅、Al₂O₃、NiO、MoO₃、ZnO、MgO、NiO、SnO₂(ii) a The polar interface material capable of forming compound between different groups comprises carbonate metal compound material Li₂CO₃、Na₂CO₃、 Cs₂CO₃(ii) a The strong polar interface materials which can form compounds among different groups comprise metal fluoride material interfaces LiF, NaF, KF, RbF, CsF and MgF₂、CaF₂(ii) a Other interface materials that interact with perovskite materials include PTFE, piezoelectric films, piezoelectric ceramics.

4. The polar interface based halide perovskite optoelectronic device of claim 1, wherein: preparing a conductive perovskite luminescent thin film luminescent device with ITO:

a. conductive substrate with ITO: sputtering an ITO raw material onto a substrate by using a magnetron sputtering technology, placing the substrate on a substrate table with a mask plate, partially shielding the substrate by using the mask plate, and partially sputtering an ITO material to be exposed;

b. cleaning treatment of a conductive substrate: carrying out pretreatment on a conductive substrate, firstly carrying out ultrasonic cleaning for 15 minutes by using seven steps of deionized water, acetone, isopropanol, deionized water and isopropanol, and then putting the conductive substrate into a UV-Ozone cleaning machine for carrying out Ozone cleaning for 15 minutes;

c. preparing a charge transport material film: placing the cleaned conductive substrate into a glass culture dish, conveying the glass culture dish into a nitrogen glove box through a transition bin of the glove box, then placing the conductive substrate on a vacuum spin-coating machine in the nitrogen glove box, dissolving a charge transfer material in a solvent, sucking a charge transfer material solution by using a liquid-moving gun, uniformly coating the charge transfer material solution on the conductive substrate, completely coating ITO (indium tin oxide) by using the charge transfer material, starting a button of the vacuum spin-coating machine to spin-coat at 3000rpm for 60s to form a film of the charge transfer material, after the spin-coating of the film of the charge transfer material is completed, placing the conductive substrate covered with the charge transfer material on a heating table to perform high-temperature annealing at 120 ℃ for 10min, and finally forming the ITO-coated charge transfer material film on the conductive substrate;

d. evaporating polar interface materials: opening a bin gate of the vacuum coating machine in the glove box in the first step, placing the conductive substrate which is taken down from the hot table and is prepared with the charge transmission material into a glass culture dish, conveying the conductive substrate into the glove box with the vacuum coating machine through a transition bin, taking out the conductive substrate prepared with the charge transmission material, placing the conductive substrate on an evaporation substrate table in the vacuum coating machine, adjusting the position of the evaporation substrate table, and closing a baffle below the substrate table;

e. spin coating a halide perovskite thin film: during spin coating, placing a conductive substrate coated with a polar interface material and a charge transport material by evaporation on a vacuum spin coating machine, uniformly coating a halide perovskite precursor solution absorbed by a liquid transfer gun on the conductive substrate coated with the polar interface material and the charge transport material by evaporation, starting a button of the vacuum spin coating machine, spin-coating for 60s at the rotating speed of 5000rpm to form a halide perovskite thin film, and placing the conductive substrate coated with the halide perovskite, the polar interface material by evaporation and the charge transport material on a hot table for high-temperature annealing at 90 ℃ for 10 min;

f. evaporation of cathode charge transport material: placing the annealed conductive substrate covered with halide perovskite, evaporated with polar interface material and covered with charge transfer material into a glass culture dish, transferring the substrate into a glove box with a vacuum coating machine through a transition bin, taking the substrate out of the glass culture dish, placing the substrate on an evaporation substrate table in the vacuum coating machine, adjusting the position of the evaporation substrate table, and closing a baffle below the substrate table; the evaporation rate of the charge transport material detected by the quartz crystal oscillator plate is displayed by the film thickness instrument, after the evaporation rate of the charge transport material displayed by the film thickness instrument is stable, the evaporation rate is stable at 0.05nm/s, a baffle below a base plate table in a vacuum coating machine is started, and the charge transport material with uniform evaporation rate can be uniformly deposited on a conductive substrate covered with halide perovskite, evaporated with a polar interface material and covered with the charge transport material;

g. evaporating an electrode: after the charge transmission material is evaporated, the charge transmission material is placed on a metal mask plate in a vacuum coating machine, the evaporation rate of an electrode detected by a quartz crystal oscillation plate is displayed through a film thickness meter, after the evaporation rate of the electrode displayed by the film thickness meter is stable, the evaporation rate is stable at 0.2nm/s, a baffle below a base plate table in the vacuum coating machine is opened, and the electrode with uniform evaporation rate is uniformly deposited on a conductive substrate covered with the charge transmission material, halide perovskite, an evaporated polar interface material and the charge transmission material.

5. A polar interface based halide perovskite optoelectronic device as claimed in claim 1 or 4 wherein: the preparation method of the polar interface on the substrate adopts magnetron sputtering, MOCVD, ALD, spraying, printing or chemical synthesis methods, and the thickness range is 0.1 nm-1000 nm.

6. A polar interface based halide perovskite optoelectronic device as claimed in claim 1 or 4 wherein: the polarity of the polar interface material is changed by regulating and controlling materials with different electronegativities, or a non-polar interface is regulated and controlled to be a polar interface, and finally the final performance of the device is regulated and controlled by changing the polarity mode of the material interface.

7. A polar interface based halide perovskite optoelectronic device as claimed in claim 1 or 4 wherein: the polar material interface is applied to various photoelectric devices, including solar cells, light emitting diodes, detectors, fluorescent films, fluorescent powder, semiconductor transistors, lasers and other photoelectric devices and materials.

8. A polar interface based halide perovskite optoelectronic device as claimed in claim 1 or 4 wherein: the polar material interface can be applied to defining the effective working area of perovskite materials or devices, further defining different working patterns, and can be expanded to be applied to perovskite materials and photoelectric devices based on different patterns.

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