A New Type Of High-efficiency Perovskite Thin-film Optoelectronic Device Was Prepared By The Scratch Coating Method

Organic-inorganic hybrid perovskite has been widely used in solar cells and other semiconductor devices owing to their excellent photophysical properties as well as low cost solution manufacturing.The power conversion efficiency(PCE)of solar cells based on the perovskite films prepared by the little-scale spin-coating method has reached 22.7%.However,the preparation of perovskite thin films by large-area,high-throughput printing methods still reported less.Therefore,how to prepare high-efficiency perovskite optoelectronic devices through printing processes will be an important direction for the future research of perovskites.Owing to a huge difference of film formation and crystallization dynamics between spin coating and print process,the preparation parameters of spin coating method is difficult to directly transfer to the printing preparation process.This is the main obstacle of printing high-quality perovskite films.Thus,developing a low-temperature printing process for perovskite materials,study and control the deposition and crystallization kinetics of perovskite in the printing process is a key factor in the low-cost,high-throughput preparation of perovskite photovoltaic devices.It is necessary to carry out exploratory research work for the above direction.To resolve the above key problems,we researched follow works:1.We prepared a flexible and large-area oriented single crystal MAPbI3 thin film via controling the nucleation and crystallization rates of the perovskite solution during the printing process.The single-crystalline perovskite microarrays film demonstrated a high degree of controlled macroscopic alignment and crystal orientation,which exhibit signifcant improvements in optical and optoelectronic properties comparing with their random counterparts,spherulitic,and nanograin films.Flexible photodetectors based on the single-crystal films showing significant anisotropy in charge transport,and the device exhibits signifcantly improved performance in all aspects by one more orders of magnitude relative to randomly oriented nanocrystalline thin film devices.(eg.The responsivity at 560 nm increases from 35 W-1 to 480 W-1 and the detectivity increases from 1.45×1011 Jones to 1.26×1012 Jones.)In addition,the bending stability and environmental stability also have a certain increase.2.Utilizing the excellent optical properties of oriented single crystal perovskite films,we prepared a visible-infrared broadband response photodetector by combining up-conversion nanoparticles(UCns,NaYF4:Yb/Er)with MAPbI3 microarrays.The devices obtained excellent NIR photodetect capability,The responsivity and detectivity at 980 nm are as high as 0.27 A W-1 and 0.76 ×1012 Jones,respectively,and due to the Plasmon effect,the optical response and detectivity in the visible light band also enhanced by a factor of three.In addition,we found that the the bilayer photodetector has excellent environmental stability,the performance only reduced by 27%when the devices exposure in 30%to 40%humidity for 1000 h.These results suggest that the composite based on perovskite and UCns is promising for constructing high-performance broadband optoelectronic devices with long-term stability.3.We studied the phase transformation behavior of the perovskite crystals during spin coating and blade coating preparation by real-time tracking technology,and we found that there is a precursor-solvent intermediate phase in the process from solution to thin film,and the intermediate phase determines the morphology and.photoelectric properties of the perovskite film.In situ GWIAXS results indicate that the rapid evaporation of the solvent inhibits the formation of the intermediate phase.In situ high-speed optical microscopy results show that the crystal nucleation and growth of direct crystallization in the Voronoi cells follow two-stage dynamic behavior,the number of nucleation and the growth rate are determined by the nature of the solvents.The results of in-situ analysis allow us to comprehensively understand the crystal structure evolution and crystal growth mechanism of perovskite.These findings provide effective ideas for designing perovskite film printing processes:a large-grained dense perovskite film with high crystal quality and photophysical properties can just obtained via direct crystallization.Under the guidance of this theory,we have prepared a MAPbI3 perovskite planar solar cell with a power conversion efficiency of 18.74%by blade-coating method.The understanding of phase transitions during spin coating and blade coating processes will provide a reliable way to print high performance perovskite devices.