Blocking wide bandgap mixed halide perovskites’ decomposition through polymer inclusion

The relatively easy tunability of perovskites’ energy gap, as well as the synthesis of mixed halide perovskites, make them highly versatile and compatible with others semiconductor materials to produce efficient tandem solar cells. However, one of the obstacles holding back the development of this technology is the poor photostability of perovskite, one of the most critical aspects of mixed halide formulations. In this work, we use a polymeric additive to improve the photostability of halide perovskites. We developed a polymer-mediated crystallization (PMC) perovskite that allowed obtaining solar cells with photovoltaic performances equal to reference perovskites (power conversion efficiency ∼17%) but with superior endurance to light exposure, demonstrated by a laser-induced photostability assessment. Furthermore, by photoluminescence mapping and terahertz spectroscopy we carried out an in-depth investigation of the photodegradation process, revealing that in PMC perovskite, halogen segregation effects can still take place but are confined to spatially limited regions of the sample.