Regensburg 2019 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 19: Hybrid and Perovskite Photovoltaics II

CPP 19.8: Talk

Tuesday, April 2, 2019, 11:30–11:45, H18

Improving the thermal stability of co-evaporated lead halide perovskites by replacing MA with Cs: Film growth and decomposition analyzed by in situ XRD — •Thomas Burwig, Paul Pistor, and Roland Scheer — Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle (Saale), Germany

Perovskites have seen a rising popularity in photovoltaic research due to their outstanding optoelectronic properties, with the most researched perovskite in this field being MAPbI₃. However, practical applications are held back by a lack of stability against atmospheric water, light and temperature. In our work we present fully inorganic caesium-lead-halide-perovskites, in which the organic MA is exchanged for caesium. We deposit thin films via dry, vacuum-based thermal co-evaporation. A specialized in situ X-ray diffraction setup allows us to monitor the crystal phase evolution over the course of the experiments. We report on the growth and thermally induced phase changes as well as the thermally induced decomposition of CsPbI₃ and CsPbBr₃ perovskites. CsPbI₃ is grown in a black, orthorhombic perovskite structure at room temperature (α′-CsPbI₃). This phase is stable in vacuum, but unstable under ambient conditions, as it undergoes a phase change to yellow, also orthorhombic δ-CsPbI₃. No such phase change was observed for CsPbBr₃. Our experiments confirm a higher thermal stability for CsPbI₃ and CsPbBr₃ as compared to the MA-lead-halides. Finally, we report on our attempts to synthesize further inorganic perovskites with improved stability.