Indexed on: 14 Jun '17Published on: 14 Jun '17Published in: Journal of Physical Chemistry Letters
While hybrid organic-inorganic perovskites are now taking center stage in photovoltaic research, thermally unstable nature of organic components will be an ultimate obstacle to commercialization. As a potential alternative, all-inorganic cesium lead halide perovskites, especially CsPbI2Br, have emerged as thermally stable and efficient photovoltaic light absorbers. However, the fundamental properties of this material have not been studied in detail. Here, the crystal formation behavior of cesium lead mixed-halide perovskites is investigated in terms of the surface morphology, crystal structure and chemical state. We discover a previously uncharacterized feature that the crystal growth and morphology evolution of CsPbI2Br are significantly influenced by annealing temperature. By evaluating perovskite films and solar cells, we confirm that optimally crystallized perovskites exhibit superior photovoltaic performance and high phase stability against humid atmosphere.