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Graduate Student Seminar - 04/20/2018

"Humidity-induced Photoluminescence Hysteresis in Cs-containing Perovskites"

by John M. Howard1,2

Advisor:  Asst. Professor Marina Leite1,2

Friday, April 20, 2018 -- 12:00 p.m.
Large Conference Room, 1207 Energy Research Facility

Abstract:  Hybrid organic-inorganic perovskites containing Cs are a promising new material for a wide variety of optoelectronic applications. However, the impact of environmental conditions on their optical and electronic properties is not fully understood. Here, we resolve and quantify the influence of distinct humidity levels on the charge carrier recombination in CsxFA1-xPb(IyBr1-y)3 perovskites. Using in situ environmental scanning photoluminescence (PL) microscopy, we spatially and spectrally resolve the light emission within a loop of critical relative humidity levels. These measurements indicate that exposure up to 35% rH increases the PL emission intensity for all Cs (10-17%) and Br (17-38%) concentrations investigated here. Spectrally, samples with larger Br concentrations exhibit PL redshift at higher humidity levels, revealing the ability of water to initiate halide segregation. Finally, most compositions considered here present hysteresis in their PL intensity upon returning to a low moisture environment, indicative of a nonreversible chemical reaction. Our findings indicate that the Cs-Br ratio influences both the spectral stability and extent of emission hysteresis. From these discoveries, we expect the fabrication of superior performing perovskite semiconductors stable under ambient to high-humidity conditions.

1Department of Materials Science and Engineering
2Institute for Research in electronics and Applied Physics

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