Light stability tests of methylammonium and formamidinium Pb-halide perovskites for solar cell applications

We have prepared perovskite [CH 3 NH 3 PbI 3 (MALI), CH 3 NH 3 PbBr 3 (MALB), NH 2 CH=NH 2 PbI 3 (FALI), and NH 2 CH=NH 2 PbBr 3 (FALB)] thin films by a one-step process on glass/TiO 2 and glass/Al 2 O 3 substrates and studied the stability of the perovskite under UV/visible light radiation up to 24 h at 1.5AM in air. After irradiation, the films were characterized by UV–vis absorption and X-ray diffraction measurements. In addition, photovoltaic performance characteristics in air were studied using different perovskites before (0 h) and after 24 h irradiation. The results revealed that Al 2 O 3 protected the perovskite crystal from degradation. However, the perovskites were unstable except for NH 2 CH=NH 2 PbI 3 under the same conditions using a TiO 2 scaffold layer.