Crystal Growth And Characterization Of Tin-Based Organic-Inorganic Perovskite

As organic/inorganic hybrid perovskite solar cells are gradually being promoted to commercial applications,the toxicity of lead has drawn people's attention,and its environmental pollution and hidden dangers of human health problems have caused concern for investors and consumers.As a candidate for replacing lead,tin has received great attention.Compared with lead-based perovskites,tin-based perovskites are more suitable for preparing solar cell due to their smaller band gaps,lower exciton binding energy,higher carrier mobility,and wider light absorption range.Although tin-based perovskites have so many advantages,devices currently prepared using tin-based perovskites do not exhibit satisfactory performance.The main reason is that Sn2+ in the perovskites is easily oxidized,resulting in a decrease in device performance.In addition,the current research reports on tin-based organic/inorganic hybrid perovskites are mainly based on polycrystalline films,and the basic properties of the materials are still controversial.Therefore,in order to further explore the potential of such materials and their intrinsic properties,it is very important to study low-defect,grain-free single crystal materials.Based on the above,we have grown MASnI3 and FASnI3 crystals and tested their physical properties.At the same time,we prepared the FASnI3 film by crystal re-dissolution technology,and studied their properties.In past studies,mixing organic cations of lead-based perovskites was an effective way to improve the performance of perovskites.Therefore,we have studied the mixing of cationic iodonium-based perovskite materials MAxFA1-xSnI3 in order to further improve the performance of tin-based perovskite materials.This paper contains five chapters and the main contents are as follows:The first chapter describes the research background and significance of organic/inorganic hybrid perovskite materials,crystal structure,crystal growth methods and related application fields.In addition,the topic selection and main research contents of this thesis are briefly explained.The second chapter describes the selected crystal growth method,the equipment for crystal growth,and the chemical reagents used in the experiments,and then introduces the main test characterization methods of the material.The third chapter describes the growth process of MASnI3 and FASnI3 bulk single crystals,as well as the characterization methods and test results of their crystal properties.In addition,FASnI3 crystal redissolution technology was used to prepare solar cell films,and the film interface was tested and characterized.The fourth chapter focuses on the characterization of a series of mixed cationic tin-based perovskite MAxFA1-xSnI3(X=0.2,0.35,0.45,0.55,0.75)crystals,and then studied MA0.35FA0.65SnI3 solar cell.The fifth chapter is a summary of the whole paper and a perspective on our future research direction.