A fully transparent perovskite thin film, device, preparation method and application

Abstract

The present invention discloses a fully transparent perovskite thin film, device, preparation method and application, belonging to the field of perovskite solar cells. It is obtained by the irreversible interaction between formamidinium cations and amine molecules in formamidinium perovskite. It has complete transparency in the visible light range, with an average visible transmittance (AVT) of not less than 77.07% and a color rendering index (CRI) of not less than 95.81. During preparation, amine gas / solution treatment is carried out on the surface of the formamidinium perovskite thin film, and an irreversible interaction occurs between external amine molecules and the relatively large-sized formamidinium cations in the lattice, and the black-phase perovskite light absorption layer is rapidly transformed into a fully transparent phase. The treatment methods include drop coating, spin coating and surface fumigation. The present invention also provides an optoelectronic device of the fully transparent perovskite thin film and its application, which are used in the fields of smart windows, building facades and electronic displays. The present invention solves the problem of the lack of a stable transparent perovskite light absorption layer in the prior art.

Description

Technical Field

[0001] The present invention belongs to the field of perovskite solar cells, and more specifically, relates to a fully transparent perovskite thin film, device, preparation method and application. Background Art

[0002] Organic-inorganic hybrid perovskite thin films have excellent properties such as high extinction coefficients, large charge transport distances, and continuously adjustable band gaps, and have great application potential in photoelectric conversion, attracting extensive research attention in the academic and industrial fields. Only after several years of development, the photoelectric conversion efficiency of perovskite solar cells (PSCs) has rapidly increased from 3.8% to 25.2%. Perovskite solar cells are composed of a transparent conductive substrate, a charge transport layer, a perovskite light-absorbing layer, and a metal electrode. The light-absorbing layers of traditional organic-inorganic hybrid perovskite solar cells are CH3NH3PbI3, CH(NH2)2PbI3, and their multi-component mixed perovskite materials. However, these perovskite light-absorbing layers are mainly black-phase and do not have light transmittance, which greatly limits the application scenarios of perovskite solar cells.

[0003] Chinese patent application with publication number CN107327056A discloses a metal halide perovskite solar cell and a corresponding curtain wall version, but it does not have high light transmittance and does not consider that the application of glass curtain walls needs to meet the indoor lighting requirements. Chinese patent application with publication number CN108625517A discloses a new type of energy-saving power generation glass curtain wall based on a transparent perovskite photovoltaic module. The visible light transmittance of the perovskite photovoltaic module provided by this invention is 50%, and the key to its transparency lies in that the perovskite light-absorbing layer is CsPbBr / MAPbBr. However, this is not truly fully transparent. In other words, this photovoltaic module mainly uses the lighter color of the CsPbBr / MAPbBr perovskite light-absorbing layer to improve the light transmittance of the photovoltaic device. In fact, true full transparency has not been achieved, and it cannot meet the requirements of higher light transmittance in some application scenarios in real life, such as smart windows, building curtain walls, electronic displays and other fields.

[0004] Therefore, there is a need to develop a new type of truly fully transparent perovskite optoelectronic thin film and device. Summary of the Invention

[0005] Aiming at the defects of the prior art, the purpose of the present invention is to provide a fully transparent perovskite thin film, device, preparation method and application. By using amine molecules to treat the FA (formamidine) - based perovskite light-absorbing layer, the black-phase perovskite light-absorbing layer can be rapidly converted into a stable fully transparent phase, aiming to solve the problem of the lack of a stable transparent perovskite light-absorbing layer in the prior art.

[0006] To achieve the above object, according to the first aspect of the present invention, a fully transparent perovskite film is provided, which is obtained by an irreversible reaction between formamidinium cations and amine molecules in formamidinium perovskite. It has complete transparency in the visible light range, with an average visible transmittance (AVT) of not less than 77.07% and a color rendering index (CRI) of not less than 95.81.

[0007] According to the second aspect of the present invention, a method for preparing a fully transparent perovskite film as described above is also provided. On the surface of the prepared formamidinium perovskite film, treatment with an amine gas / solution is carried out. The lone pair electrons of the nitrogen atom in the external amine molecule interact with the positively charged N in the formamidinium cation with a larger size in the lattice, followed by proton exchange, so that the black-phase perovskite photoabsorber layer is rapidly converted into a fully transparent phase. The treatment methods include drop coating, spin coating, and surface fumigation.

[0008] Furthermore, the amine gas / solution is selected from one or a mixture of ammonia gas, aqueous ammonia, methylamine in methanol solution, methylamine aqueous solution, ethylamine in ethanol solution, ethylamine aqueous solution, propylamine in propanol solution, and propylamine aqueous solution.

[0009] Furthermore, the chemical general formula of the perovskite in the formamidinium perovskite film component is ABX3, where X represents a halogen element ion, X is selected from one or more of I, Br, and Cl, the value range of X is 0 < X < 1, B is a Pb ion, and A is one or more of formamidinium ions and amine molecules.

[0010] According to the third aspect of the present invention, an optoelectronic device comprising the fully transparent perovskite film as described above is provided, which includes a fully transparent perovskite solar cell.

[0011] According to the fourth aspect of the present invention, a method for preparing a fully transparent perovskite solar cell as described above is also provided, which includes the following steps:

[0012] S1: Prepare an electron transport layer on a transparent conductive substrate that has been cleaned and UV-treated;

[0013] S2: In an oxygen-free and water-free environment, spin coat the perovskite photoabsorber layer precursor on the surface of the electron transport layer, perform annealing, and naturally cool to room temperature. Treat the perovskite film with an amine gas / solution. An irreversible interaction occurs between the amine molecules and the formamidinium cations with a larger size in the lattice, followed by a proton exchange reaction, and the black-phase perovskite photoabsorber layer is rapidly converted into a fully transparent phase;

[0014] S3: Prepare a hole transport layer on the surface of the fully transparent perovskite photoabsorber layer;

[0015] S4: Deposit a metal electrode on the surface of the hole transport layer.

[0016] Further, in step S2, the treatment method is surface drop coating, spin coating or / and surface fumigation.

[0017] Further, in step S2, the amine gas / solution is selected from one or a mixture of ammonia gas, aqueous ammonia, methylamine methanol solution, methylamine aqueous solution, ethylamine methanol solution, ethylamine aqueous solution, propylamine methanol solution and propylamine aqueous solution.

[0018] Further, the transparent conductive substrate is glass or a polymer sheet covered with ITO, ATO, IZO or FTO thin film, the electron transport layer is a composite formed by one or more of TiO2, SnO2 or ZnO, and the materials used for the hole transport layer are one or more of spiro-OMeTAD, P3HT, PEDOT, PTA, LaNiO, NiO, CuSCN.

[0019] In engineering practice, the structure of the fully transparent perovskite solar cell includes a conductive substrate, an electron transport layer, a perovskite light absorption layer, a hole transport layer and an electrode layer stacked in sequence. The perovskite component is an FA-based perovskite component, including pure-phase FAPbI3 and mixed multi-component perovskite FA 1-x MA x PbX3. When the perovskite light absorption layer precursor is spin-coated on the surface of the electron transport layer, the spin-coating speed is 2000 rpm to 5000 rpm, and the spin-coating time is 10 s to 45 s. Among them, 100 μL to 200 μL of an antisolvent such as diethyl ether or chlorobenzene is dropped at the 12th s to 20th s during spin coating. The annealing temperature is 100 °C to 180 °C, and the annealing time is 10 min to 30 min. The thickness of the deposited metal electrode is 60 nm to 80 nm.

[0020] According to the fifth aspect of the present invention, the application of the optoelectronic device as described above is used in the fields of smart windows, building facades and electronic displays.

[0021] Generally speaking, compared with the prior art by the above technical solutions conceived by the present invention, the following beneficial effects are obtained:

[0022] The present invention provides a fully transparent perovskite optoelectronic thin film, which treats the FA-based perovskite light absorption layer with amine molecules. The lone pair electrons of the nitrogen atoms in the amine molecules interact with the positively charged N in the formamidinium cations with larger sizes in the lattice, and then proton exchange occurs to replace part of the FA +The cations are thus transformed into a stable, transparent-phase perovskite light-absorbing layer. On this basis, optoelectronic devices with fully transparent perovskite thin films can be fabricated, and in particular, a new stable fully transparent perovskite solar cell can be obtained. The perovskite solar cell prepared by the present invention has complete transparency in the visible light range, with an average visible transmittance (AVT) of 77.07% and a color rendering index (CRI) of 95.81. At the same time, the fabricated fully transparent perovskite solar cell has good photovoltaic performance. The present invention provides a method for fabricating a fully transparent perovskite solar cell, which has a simple fabrication process, low cost, high repeatability, and excellent stability. Description of the Drawings

[0023] Figure 1 It is the visible light transmittance spectrum of the fully transparent perovskite solar cell fabricated in this embodiment.

[0024] Figure 2 It is the photoelectric conversion efficiency spectrum of the fully transparent perovskite solar cell fabricated in this embodiment.

[0025] Figure 3 It is a schematic diagram of the principle of the interaction between methylamine molecules and formamidinium cations. Detailed Description of the Embodiments

[0026] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] Example 1

[0028] (1) Cleaning of the substrate

[0029] Place the FTO conductive glass in an ultrasonic cleaning instrument and ultrasonically clean it with deionized water, acetone, isopropanol, and ethanol respectively. The ultrasonic cleaning time for each step is 30 min, and then dry it with a nitrogen gun. Subsequently, irradiate the dried FTO conductive glass substrate under UV for 20 minutes for later use.

[0030] (2) Preparation of the electron transport layer

[0031] The prepared TiO2 solution (369 mL of titanium isopropoxide, 35 mL of 2 M hydrochloric acid solution added to 5.06 mL of anhydrous ethanol solution) was spin-coated on a clean FTO conductive glass substrate at a speed of 2000 rpm for 35 s, then annealed at 100 °C for 10 min, and cooled to room temperature to obtain a relatively dense TiO2 thin film. Subsequently, further on the surface of the dense layer, an ethanol solution of 15 wt.% TiO2 mesoporous slurry was rotated at a speed of 6000 rpm for 50 s, and dried at 100 °C for 10 min to remove the excess organic dispersant. Then, it was calcined at 500 °C for 1 h to obtain a mesoporous TiO2 layer.

[0032] (3) Preparation of perovskite light absorption layer

[0033] In the glove box, the perovskite precursor solution (1.2 M FAI and 1.2 M PbI2 dissolved in 1 ml of a mixed solvent with a volume ratio of DMF (N,N-dimethylformamide): DMSO (dimethyl sulfoxide) = 9:1, stirred in the dark at room temperature until completely dissolved) was spin-coated on the surface of the electron transport layer at a speed of 4000 rpm for 30 s, and 100 μL of the antisolvent chlorobenzene was added dropwise at the 16th s of spin-coating. Subsequently, it was annealed at 150 °C for 10 min and naturally cooled to room temperature. Then, 10 μL of methylamine ethanol solution was spin-coated on the perovskite thin film to prepare a fully transparent perovskite absorption layer.

[0034] (4) Preparation of hole transport layer

[0035] Spiro-OMeTAD (concentration of 73 mg / ml) was spin-coated on the prepared absorption layer at a speed of 4000 rpm, and then oxidized in a dry environment for 8 h.

[0036] (5) Preparation of gold electrode

[0037] 0.19 g of pure gold (>99.999%) was evaporated onto the high-quality Spiro-OMeTAD thin film obtained in step (4) covered with a mask plate using a metal evaporation coater to obtain a dense and high-quality gold electrode, completing the composition of a complete device.

[0038] Placing the fully transparent perovskite solar cell prepared in this example under sunlight, it can be clearly observed that the prepared perovskite solar cell has complete transparency in the visible light range.

[0039] Figure 1 This is the visible light transmittance spectrum of the fully transparent perovskite solar cell prepared in this example. The results show that the average visible transmittance (AVT) of the prepared fully transparent perovskite solar cell is 77.07%.

[0040] Figure 2 Photovoltaic conversion efficiency spectrum of the all - transparent perovskite solar cell prepared in this embodiment. As can be seen from the figure, the short - circuit current density (JSC) of this device is 0.47 mA / cm 2 , the open - circuit voltage (VOC) is 0.75 V, the fill factor (FF) is 0.59, and the corresponding power conversion efficiency is 0.21%.

[0041] Example 2

[0042] (1) Cleaning of the substrate

[0043] Place the FTO conductive glass in an ultrasonic cleaning instrument and ultrasonically clean it with deionized water, acetone, isopropanol, and ethanol respectively. The ultrasonic cleaning time for each step is 30 min, and then dry it with a nitrogen gun. Subsequently, irradiate the dried FTO conductive glass substrate under UV for 20 minutes for later use.

[0044] (2) Preparation of the electron transport layer

[0045] Spin - coat the prepared TiO2 solution (369 μL of titanium isopropoxide, 35 μL of 2 M hydrochloric acid solution added to 5.06 mL of anhydrous ethanol solution) on the clean FTO conductive glass substrate at a speed of 3000 rpm for 30 s, then anneal it at 120 °C for 10 min and cool it to room temperature to obtain a relatively dense TiO2 thin film. Subsequently, further spin - coat an ethanol solution of 15 wt.% TiO2 mesoporous slurry on the surface of the dense layer at a speed of 5000 rpm for 50 s, and dry it at 100 °C for 10 min to remove the excess organic dispersant. Then, calcine it at 500 °C for 1 h to obtain the mesoporous TiO2 layer.

[0046] (3) Preparation of the perovskite light - absorbing layer

[0047] In the glove box, spin - coat the perovskite precursor solution (1.05 mol FAI, 1.1 mol PbI2, 0.05 mol MAI dissolved in 1 ml of a mixed solvent with a volume ratio of DMF:DMSO = 4:1, stirred in the dark at room temperature until completely dissolved) on the surface of the electron transport layer at a speed of 3000 rpm for 35 s, and add 150 μL of the antisolvent chlorobenzene at the 15th s of spin - coating. Subsequently, anneal it at 160 °C for 15 min and cool it naturally to room temperature. Then spin - coat 5 μL of methylamine ethanol solution on the perovskite thin film to prepare the all - transparent perovskite light - absorbing layer.

[0048] (4) Preparation of the hole transport layer

[0049] Spin-coat spiro-OMeTAD (concentration: 73 mg / ml) on the prepared absorption layer at a speed of 4000 rpm, and then oxidize it in a dry environment for 10 h.

[0050] (5) Preparation of gold electrodes

[0051] Use a metal evaporation coating instrument to evaporate 0.21 g of pure gold (>99.999%) onto the high-quality Spiro-OMeTAD thin film obtained in step 4) covered with a mask plate to obtain a dense and high-quality gold electrode, thus completing the composition of a complete device.

[0052] Example 3

[0053] The difference between this example and Example 1 is as follows:

[0054] S2: In an oxygen-free and water-free environment, spin-coat the perovskite light absorption layer precursor on the surface of the electron transport layer, perform annealing, and naturally cool to room temperature. Treat the perovskite thin film by surface fumigation with ammonia gas. The black-phase perovskite light absorption layer is rapidly converted into a fully transparent phase. The component of the formamidinium perovskite thin film is a mixed multi-perovskite FA1-xMAxPbI3, where X = 0.3.

[0055] The perovskite solar cell prepared in this example has complete transparency in the visible light range, with an average visible transmittance AVT of not less than 77.07% and a color rendering index CRI of not less than 95.81.

[0056] Example 4

[0057] The difference between this example and Example 1 is as follows:

[0058] S2: In an oxygen-free and water-free environment, spin-coat the perovskite light absorption layer precursor on the surface of the electron transport layer, perform annealing, and naturally cool to room temperature. Treat the perovskite thin film by drop-coating with a propanolamine solution. The black-phase perovskite light absorption layer is rapidly converted into a fully transparent phase. The component of the formamidinium perovskite thin film is a pure phase FAPbI3.

[0059] The perovskite solar cell prepared in this example has complete transparency in the visible light range, with an average visible transmittance AVT of not less than 77.07% and a color rendering index CRI of not less than 95.81.

[0060] In the present invention, among ammonia gas, aqueous ammonia, methanolamine solution, aqueous methylamine solution, ethanolamine solution, aqueous ethylamine solution, propanolamine solution, and aqueous propylamine solution, they all have the characteristic of N atoms with lone pair electrons, and can all achieve the irreversible interaction between amine molecules and the relatively large-sized FA + cations in the crystal lattice. This irreversible interaction makes the performance of the prepared fully transparent perovskite thin film stable.

[0061] Figure 3 It is a schematic diagram of the principle of the interaction between methylamine molecules and formamidinium cations. As can be seen from the figure, the N atom in MA (methylamine molecule) has a pair of lone pair electrons, while the N atom in the formamidinium cation is positively charged due to the lack of one electron. When the two come into contact, MA attacks FA+, as Figure 3 shown by the arrow, which belongs to a nucleophilic reaction. A similar donor and acceptor reaction occurs to form an intermediate complex FAPbI3---MA. Subsequently, a proton exchange occurs between the N in the formamidinium cation and the N in the methylamine molecule, thus forming MAPbI3---FA. MAPbI3---FA is a transparent and stable phase. Different from volatile MA, the vapor pressure of FA at 25 °C is much lower, being 45 kPa, which makes it difficult to escape from the lattice. Therefore, the FA located in the lattice stabilizes the transparent FA-MAPbI3 film, and its transparency remains unchanged even after the sample is removed from the MA atmosphere, showing good stability.

[0062] In the present invention, the transparent conductive substrate is glass or a polymer sheet covered with ITO, ATO, IZO or FTO thin films. The electron transport layer is a composite formed by one or more of TiO2, SnO2 or ZnO. The materials used for the hole transport layer are one or more of spiro-OMeTAD, P3HT, PEDOT, PTA, LaNiO, NiO, CuSCN. The selection of the above materials is flexibly made according to the actual engineering situation. The above materials of the transparent conductive substrate, electron transport layer and hole transport layer are all mature and common materials, and are widely used in current all-black perovskite thin film batteries.

[0063] The all-transparent perovskite solar cell prepared by the present invention has good photovoltaic (PV) performance and can be widely applied to fields such as smart windows, building facades, electronic displays, etc. It not only meets the light transmission requirements but also meets the requirements of green energy conservation, can enrich the application fields and application scenarios of photovoltaics, and has extremely important scientific significance and social value.

[0064] It is easy for those skilled in the art to understand that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A fully transparent perovskite thin film, characterized in that, It is obtained by an irreversible reaction between formamidinium cations and amine molecules in formamidinium perovskite. Specifically, on the surface of the prepared formamidinium perovskite thin film, treatment with an amine solution is carried out. An irreversible interaction occurs between external amine molecules and formamidinium cations with larger sizes in the lattice, and the black-phase perovskite light absorption layer is rapidly converted into a fully transparent phase. The treatment methods include drop coating, spin coating, and / or surface fumigation. The amine solution is selected from one or a mixture of two of methylamine methanol solution and methylamine aqueous solution. The chemical general formula of perovskite in the formamidinium perovskite thin film component is FA 1-x MA x PbI3, X = 0.3, When the amine molecule and the formamidinium cation come into contact, the lone pair electrons of the nitrogen atom in the amine molecule interact with the positively charged N in the formamidinium cation with a larger size in the lattice to form an intermediate complex FAPbI3---MA. Subsequently, a proton exchange occurs between the N in the formamidinium cation and the N of the methylamine molecule to form a transparent and stable phase MAPbI3---FA. It has complete transparency in the visible light range, the average visible transmittance AVT is not less than 77.07%, and the color rendering index CRI is not less than 95.

81.

2. An optoelectronic device comprising the fully transparent perovskite thin film as claimed in claim 1, which includes a fully transparent perovskite solar cell.

3. A method for preparing the all - transparent perovskite solar cell according to claim 2, characterized in that, It includes the following steps: S1: Prepare an electron transport layer on a transparent conductive substrate that has been cleaned and UV-treated. S2: In an oxygen-free and water-free environment, spin coat the perovskite light absorption layer precursor on the surface of the electron transport layer, perform annealing, and naturally cool to room temperature. Treat the perovskite thin film with an amine solution, and an irreversible reaction occurs between the amine molecule and the formamidinium cation with a larger size in the lattice, and the black-phase perovskite light absorption layer is rapidly converted into a fully transparent phase. S3: Prepare a hole transport layer on the surface of the fully transparent perovskite light absorption layer. S4: Deposit a metal electrode on the surface of the hole transport layer.

4. The method according to claim 3, characterized in that, In step S2, the treatment method is surface drop coating, spin coating, or / and surface fumigation.

5. The method according to claim 4, wherein In step S2, the amine solution is selected from one or a mixture of two of methylamine methanol solution and methylamine aqueous solution.

6. The method according to claim 5, wherein The transparent conductive substrate is glass or a polymer sheet covered with an ITO, ATO, IZO, or FTO thin film. The electron transport layer is a composite formed by one or more of TiO2, SnO2, or ZnO. The materials used for the hole transport layer are one or more of spiro-OMeTAD, P3HT, PEDOT, PTA, LaNiO, NiO, CuSCN.

7. The application of the optoelectronic device according to claim 2, wherein, It is used in the fields of smart windows, building facades, and electronic displays.

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