Ion Migration‐Induced Amorphization and Phase Segregation as a Degradation Mechanism in Planar Perovskite Solar Cells. Issue 25 (2nd June 2020) - Di Girolamo, Diego
Abstract: The operation of halide perovskite optoelectronic devices, including solar cells and LEDs, is strongly influenced by the mobility of ions comprising the crystal structure. This peculiarity is particularly true when considering the long‐term stability of devices. A detailed understanding of the ion migration‐driven degradation pathways is critical to design effective stabilization strategies. Nonetheless, despite substantial research in this first decade of perovskite photovoltaics, the long‐term effects of ion migration remain elusive due to the complex chemistry of lead halide perovskites. By linking materials chemistry to device optoelectronics, this study highlights that electrical bias‐induced perovskite amorphization and phase segregation is a crucial degradation mechanism in planar mixed halide perovskite solar cells. Depending on the biasing potential and the injected charge, halide segregation occurs, forming crystalline iodide‐rich domains, which govern light emission and participate in light absorption and photocurrent generation. Additionally, the loss of crystallinity limits charge collection efficiency and eventually degrades the device performance. Abstract : A multi‐technique in situ structural and optoelectronic characterization on planar perovskite solar cells reveals perovskite amorphization and phase segregation as the crucial degradation mechanisms due to ion migration on a daily timescale. The degradation has a severe negative impact on the charge collection, which reduces the photocurrent and the power conversion efficiency. The mechanism is partially reversible after rest in the dark.