Research On Fabrication Of Lead-based Perovskite Films For Optoelectronic Applications

In recent years,perovskite materials have attracted wide attention by domestic and foreign researchers due to their excellent photoelectric properties.At present,the certificated efficiency of organic-inorganic hybrid perovskite solar cells in laboratory has exceeded 25%,showing great application potential.However,there are hurdles for their commercialization because of the humidity and thermal instability of hybrid perovskites.Partially or completely replacing organic groups via Cs ion can greatly improve the humidity and thermal stability of perovskite materials.Therefore,the main research work of this thesis focuses on the preparation process of stable tri-cation and all-inorganic lead-based perovskite materials and their optoelectronic devices.First,the application of tri-cation perovskite as a photosensitive layer in visible light photodetector is successfully verified,and its working mechanism is analyzed in depth.Secondly,for the wide band gap Cs Pb Br₃ perovskite with more stable intrinsic components,the solvent engineering method is introduced into the preparation process to realize a high-performance flexible photodetector.Furthermore,the use of mixed-halide and thin film optimization process effectively broadens the response of this type of photodetector in the visible light band.Finally,the black-phase stabilization,preparation process and photovoltaic application of all-inorganic Cs Pb I₃ perovskite are explored.The specific research contents are as follows:We prepare the trip-cation perovskite of?Cs Pb I₃?_0.05[?FAPb I₃?_0.83?MAPb Br₃?_0.17]_0.95,and use it as a light-sensitive layer for a light-visible photodetector.The height of the Schottky barrier formed between the indium tin oxide?ITO?and the perovskite layer is found to be significantly reduced when illuminated,which can effectively promote the transport and collection of carriers.Operating at a bias of 2 V,the photodetectors exhibit a large light on/off ratio of 10⁵upon illumination at 635 nm,high specific detectivity of10¹³ Jones,3d B bandwidth of 0.82 MHz.Most importantly,the device without encapsulation still show nearly consistent and stable photoelectronic properties after being kept in ambient air for 2 months.The research expands the application of tri-cation perovskites in the field of optoelectronic photodetection and provides a low-cost solution for high-speed visible photodetectors.An improved low-temperature one-step method is proposed to successfully prepare high-quality inorganic Cs Pb Br₃ perovskite films and high-performance flexible photodetectors.The introduction of solvent engineering into the low-temperature post-treatment process of the all-inorganic lead-based perovskite film significantly improves the morphology and optoelectronic properties of the perovskite film.The flexible photodetector device based on the film has a good response from blind ultraviolet to visible light?540 nm?.Furthermore,mechanical flexibilty test demonstrates that our flexible photodetectors would not be influenced by the stress of external bending moments.At the same time,the photoelectric performance of the device without encapsulation before and after storage in ambient air for months is compared,and it is found that there is no difference in performance,which confirmes the excellent humidity stability of the inorganic lead halide perovskite.This work demonstrates the application of inorganic perovskite detection in the solar-blind ultraviolet,broadens the response range of perovskite in the ultraviolet,and demonstrates the full-spectrum detection capability of perovskites.The mixed-halide strategy is adopted to broaden the response of the Cs Pb Br₃photodetector in the visible light.Partially replacing Cs Br and Pb Br₂ via Cs I and Pb I₂ can readily prepare Cs Pb I₂Br and Cs Pb IBr₂ perovskite films,thereby realizing the tuning of the perovskite optical band-gap.In order to solve the problem of pinholes in the film,the rapid crystallization method is explored,and the Cs Pb I₂Br and Cs Pb IBr₂ perovskites with dense and uniform grain size are prepared and successfully applied as photosensitive layers in visible light photodetectors.We propose a new mediator-antisolvent strategy to fabricate efficient and stable all-inorganic Cs Pb I₃ perovskite solar cells.When the PCBM(phenyl-C₆₁-butyric acid methyl ester)is applied during the spin-coating process,the grain size of Cs Pb I₃ is decreased from micrometer to about 200 nm due to the change of crystallization kinetics process of film growth,which is beneficial for the stabilization of black-phase Cs Pb I₃.Furthermore,MAI?CH₃NH₃I?additive is applied to improve the crystallinity and photoelectric properties without introducing organic groups in the final film.Finally,Cs Pb I₃ solar cells are fabricated and achieve a high power conversion efficiency of 16.04%.The device being stored in glove-box still remains 95%of the initial PCE over 1000 h,which shows superior storage stability.