Perovskite Solar Cells. Excited State Chemistry of Lead Halide Hybrid Perovskites

Abstract

With the emergence of highly efficient lead halide perovskites there is a need to understand the excited state behavior and charge separation events following photoexcitation. The excited state characterization using emission and transient absorption spectroscopy has allowed us to probe the charge recombination processes. Of particular interest are mixed halide lead perovskites (e.g.,CH3NH3PbI3-xBrx) which offer flexibility of tuning bandgap. Interestingly, they also undergo phase segregation to create Iodine-rich and Bromide- rich regions when subjected to visible irradiation. This intriguing aspect of halide ion movement in these mixed halide films can be tracked from the changes in the photoluminescence and absorption spectra. The photovoltaic performance of perovskite solar cells with varying degree of halide treatment will also be discussed.