Preparation Of Cu₂O And MAPbI₃ Thin Films And Their Application In Solar Cells

In recent years,the highest conversion efficiency of organic-inorganic hybrid perovskite solar cells?PSCs?represented by CH₃NH₃PbI₃?MAPbI₃?has exceeded 22%,which is comparable to that of polysilicon solar cells.However,the hole transporting materials?HTMs?used in PSCs are expensive,hole mobility is low and stability is poor,which is not conducive to the industrial development of PSCs.The use of inorganic HTMs can furtherly reduce the cost and improve the stability of the battery.The main inorganic HTMs are NiO,CuSCN,CuI,Cu2O and so on.Among them,Cu2O has the advantages of abundant reserves and hole mobility is high.At the same time,perovskite as the core layer of PSCs,the quality of which directly affects the performance of the device.In this paper,the preparation of p-type Cu₂O thin film and the optimization of MAPbI₃ thin film were studied,and the inversion plane PSCs were constructed.This article mainly focuses on the following aspects:?1?The preparation of Cu₂O film and its application in PSCs.Due to pyrolysis,the film deposited by direct electron beam evaporation are mixtures of Cu₂O and Cu.When annealed in the air with the increase of annealing temperature,the composition of the film changed to pure Cu₂O from mixture and then to pure CuO due to oxidation.When the annealing temperature is in the range of 100¹50°C,a smooth,uniform and non porous Cu₂O film can be obtained,and the average transmission rate of which is70%,the optical band gap is about 2.5 eV,and the HOMO level is about-5.32 eV,and the resistivity is about 5×10³?·cm,and the Hall mobility is about 30 cm² V^-1 s^-1.Applied to inverted plane PSCs,the highest efficiency achieving 6.84%when the thickness of Cu₂O film is about 40 nm.But the efficiency is lower than that of PEDOT:PSS as HTMs.This is mainly due to the poor wetting of perovskite precursor in the Cu₂O film,and has a large number of microporous holes in the absorption layer,which increase the leakage current.However,when Cu₂O/PEDOT:PSS double-HTMs are used,the performance of the battery deteriorated because PEDOT:PSS has a strong corrosive action on Cu₂O.?2?One step preparation and optimization of MAPbI3 thin film.When a certain amount of methylamine?MA⁰?ethanol solution is added to the precursor of perovskite,the imbalance of the ratio of the precursor solution can be effectively reduced,and the formation of the defects in the MAPbI3 film can be suppressed and the quality of the crystallization can be improved.When the amount of MA⁰ ethanol solution added to40?l/ml,the efficiency of PSCs increased from 8.17%to 9.86%.When MAPbI₃ thin film were prepared by solvent annealing,dropping temperature had a great influence on the morphology and properties of it.When the 10?l DMF was added at 100°C,and the MAPbI₃ thin film prepared after annealing for 10 min had larger particle size and higher quality,when used in PSCs,the efficiency increased to 11.2%.?3?The preparation of MAPbI₃ thin film by Vapor-assisted solution.When the experiment is carried out in a rapid-rising tube furnace,a large particle size,dense and uniform MAPbI3 thin film can be prepared at a lower temperature in a shorter time.However,there is a clear grain boundary between the particles,and the thin film has a low preferred growth orientation and fluorescence intensity,indicateing that the quality of the film is poor and the defect density is high.When the film is treated with MA⁰gas,the performance of the film is improved to a certain extent.