Preparation And Properties Of Lead Halide Perovskite Materials

Lead halide perovskite materials CH₃NH₃PbX₃?X=Cl,Br,I?have the characteristics of high carrier mobility,high light absorption coefficient,long carrier diffusion length,etc.,and thus have potential application prospects in many fields,such as solar cells,light-emitting diodes,detectors,thermoelectricity,etc.,which have attracted extensive attentions worldwide.At present,the research on this kind of material mainly focuses on the fields of solar films and quantum dot luminescence,however,there are many problems exiting in the uniformity and stability of the films and quantum dots,which limit their excellent performance and large-scale applications.Bulk single crystal,whose atoms arranged strictly according to crystallography,is a kind of nearly perfect material,which is also an ideal material to measure the intrinsic properties of CH₃NH₃PbX₃ material.In this paper,we studied the growth of lead halide perovskite crystals and characterized the thermal,optical,electrical and mechanical properties of the as-grown crystals.The main research results are summarized as follows:1.The CH₃NH₃PbBr₃ perovskite crystals were grown by several methods,and the advantages and disadvantages of different growth methods were compared.The properties,such as light transmittance,fluorescence lifetime,photoluminescence,hardness and young's modulus,of crystals prepared by inverse temperature crystallization method were investigated.The transmittance reached 86.6%in the range of 400¹500 nm.The emission peak position of crystal is located at 527 nm under the 300 nm excitation.The hardness and Young's modulus are 0.34 GPa and 19.5 GPa,respectively.2.The CH₃NH₃PbBr_3-xI_x mixed crystals were grown by several methods,the crystallization habits were studied and the related properties of mixed crystals grown by inverse temperature method were studied.It was found that as the concentration of I ion increased,the exposed surfaces of the crystals gradually changed from square to lateral exposed shape,and the transmittance and luminescence intensity decreased slightly,while the hardness and Young's modulus were close to that of the CH₃NH₃PbBr₃ crystal.3.CH₃NH₃PbBr_3-xI_x thin films were prepared on glass and paper substrates by an inkjet printing method,respectively.The films observed by microscope were composed of small grains with square structures,and the sizes of them were about 20¹00?m,and dendrite was easier to be observed when the adding of I ion;By printing the solution prepared with DMSO on the paper substrate,the grains tend to emit brighter green light under 480nm excitation.4.The silk fabric/CH₃NH₃PbBr_3-x-x I_x/poly?3,4-ethoxylenedioxythiophene?composites were prepared by an vapor polymerization method,and the electrical conductivity and Seebeck coefficient were measured.The power factor in the range of 0.004⁰.01?Wm^-1K^-2 was obtained for the as-prepared composites at room temperature.