Date 2021-08-24 
Time 16:00 
Title Microstructural Evaluation of Phase Instability in Large Bandgap (FAPbI3)x(MAPbBr3)1-x Perovskites 

■       : Microstructural Evaluation of Phase Instability in Large Bandgap

                (FAPbI3)x(MAPbBr3)1-x Perovskites


■       : Dr. Jae Sung YUN

■       : 2021 8월 24()  오후 4  

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■ H o s t  : 신병하 교수 

■ Abstract : Organic-inorganic halide perovskites (OIHPs) have remarkably improved their optoelectronic performances in the recent years. Solar cells fabricated using mixed-cations and mixed-halides have outperformed single-cation and single-halide counterparts. Yet, a systematic evaluation of the microstructural behaviour of mixed perovskites is still required due to compositional dependent photo-instability. Here, we explore microstructural inhomogeneity in (FAPbI3)x(MAPbBr3)1-x using various advanced scanning probe microscopy techniques. Contact potential difference (CPD) maps measured by Kelvin probe force microscopy (KPFM) reveal an increase of lower CPD grains corresponding to the flat polymorph grains in the topographical map as MAPbBr3 concentration is increased. Chemical component analysis reveals the nature of these flat grains being rich in MA, Pb, and I. Spectral photoluminescence shows clear compositional dependent phase segregation as MAPbBr3 increases which is responsible for the formation of the flat grains. Bias-dependent piezo-response force microscopy (PFM) measurements confirm ions are vigorously migrated on the flat grains resulting in hysteretic dynamics in piezoresponse-electric bias (P-E) loop. Lastly, light assisted KPFM measurements reveals that the flat grains contribute to phase segregation. With various microstructural characterizations, our results provide that the flat grains as defect sites are detrimental to phase segregation and ion migration