Long Minority-Carrier Diffusion Length and Low Surface-Recombination Velocity in Inorganic Lead-Free CsSnI3 Perovskite Crystal for Solar Cells

Abstract

Sn-based perovskites are promising Pb-free photovoltaic materials with an ideal 1.3 eV bandgap. However, to date, Sn-based thin film perovskite solar cells have yielded relatively low power conversion efficiencies (PCEs). This is traced to their poor photophysical properties (i.e., short diffusion lengths (<30 nm) and two orders of magnitude higher defect densities) than Pb-based systems. Herein, it is revealed that melt-synthesized cesium tin iodide (CsSnI3) ingots containing high-quality large single crystal (SC) grains transcend these fundamental limitations.