 The optoelectronic properties of the mixed hybrid lead halide perovskite CH3 and H3PBI3-XClX have been subject to numerous recent studies related to its extraordinary capabilities as an absorber material in thin film solar cells. The observed influence of phonon coupling and excitonic effects on charge carrier dynamics suggests that low-temperature phenomena can give valuable additional insights into the underlying physics. This article was authored by Christian Werenfenig, Mingxian Liu, Henry J. Snaith, and others.