Ruf, F., Rietz, P., Aygueler, M., Kelz, I., Docampo, P., Kalt, H. & Hetterich, M. (2018) The Bandgap as a Moving Target: Reversible Bandgap Instabilities in Multiple-Cation Mixed-Halide Perovskite Solar Cells. ACS ENERGY LETTERS , 3(12), 2995-3001.