How Ion Migration Dictates Perovskite Solar Cell Performance and Stability

The thermodynamic and redox properties of halide perovskites provide a strong driving force for hole trapping and oxidation of iodide species. In particular this becomes a factor when the perovskite solar cell is operated under open circuit conditions. The accumulated holes participate in the oxidation of iodide and expulsion of I₂. The mobility of halides and their susceptibility to hole-induced oxidation play a crucial role in determining the long-term stability of metal halide perovskite solar cells. Although passivation of 3D perovskites using 2D perovskites has been reported widely, the instability of the 2D/3D interface during long term solar cell operation is apprent. The cation migration under light and heat significantly alters the 2D/3D interface, thus affecting the solar cell performance. In-situ spectroscopic measurements of halide ion and cation migration, and their effect on solar cell performance will be discussed.