Hydration of mixed halide perovskites investigated by Fourier transform infrared spectroscopy

Abstract

The mixed lead halide perovskites are promising candidates for solar cells, but the intrinsic instabilities due to phase segregation, halide migration, and hydration hinder the practical applications. Currently, less attention is paid to the humidity induced degradation. This important issue of mixed halide perovskites is now investigated by Fourier transform infrared (FTIR) spectroscopy. After hydration of CH3NH3Pb(I1-xBrx)3, a broad band at around 3200 cm-1 of -OH vibration appears in the FTIR spectra and the bands in the range of 1200-1700 cm-1 become much stronger. The dominant FTIR mode at 1660 cm-1 due to the intermediate complex is sensitive on hydration, implying it could be used as a characteristic peak to evaluate the hydration degree of mixed halide perovskites. These information are of interest to optimize the crystal structure of this material to improve the stability so that to promote the photovoltaic applications.