Preparation Of Halide Perovskite In Air And Study On The Exciton-phonon Interaction In It

CsPbX3 was considered as a promising luminescent material because of its good environmental stability,durability and excellent optoelectrical properties.Two-dimensional(2D)perovskites with bulk organic cations have attracted extensive attention in light-emitting devices and photovoltaics due to their robust environment stability,tunable luminescent color,strong exciton binding and promising efficiency.However,some inherent exciton mechanism in these materials still need to be elucidated.For preparation of the highly bright and durable CsPbBr3 film,we respectively adopted one-step solution method and two-step solution method in normal air humidity.During the preparation process,to find the optimal conditions,we characterized the basic physical properties of the samples(surface morphology,crystallinity,luminescence properties,etc.),and carefully analyzed their physical principles.Finally,we compared the advantages and disadvantages of these two methods.Distinct acoustic phonon-exciton interaction,which was firstly observed in perovskite,was discovered in our established highly luminescent and durable CsPbBr3 film.The acoustic phonon-exciton coupling was induced by strong exciton confinement(～70 meV exciton binding energy)and accompanied with large phonon energy ascribed to local vibration modes.We also prepared quasi-2D(PEA)2(CsPbBr3)n-1PbBr4 material.The PL、SEM and PXRD were used to analyze the exciton-phonon interaction in the two dimensional(PEA)2(CsPbBr3)n-1PbBr4 with different layers of PbBr4.In the 2D perovskite with large n,the band gap will move with the temperature change,this mechanism can be dominated by thermal expansion effect,which gradually changed into exciton-phonon interaction in the(PEA)2PbBr4 phase at n=1,indicating that the exciton-phonon interaction was enhanced by the thinner quantum well structure.Further analysis shows that the enhanced exciton-exciton interaction was due to the Frohlich interaction from longitudinal optical phonon-exciton,rather than the acoustic phonon-exciton coupling.We believed that our results would benefit the further optimization of two-dimensional perovskite-based light-emitting devices.