Materials chemistry approach for efficient lead-free tin halide perovskite solar cells

Abstract

The commercial development of perovskite-based photovoltaics is hindered by the toxicity of lead perovskite. Although tin perovskite is a promising alternative, the power conversion efficiency of tin perovskite solar cells has not reached levels comparable to the lead-based devices. Several factors, including the facile oxidation of tin(II) to tin(IV) and difficulties in controlling the morphology of the perovskite layers, are responsible for the lower efficiency. By closely integrating the development of high-purity materials and improved fabrication methods with extensive material characterization, we have been able to improve the performance of tin-based perovskite devices. In this work, highly purified precursor materials for tin perovskites are introduced, together with fabrication methods for pinhole-free and uniform tin perovskite films. The oxidation of tin(II) to tin(IV) during the fabrication process is suppressed by an in situ reducing treatment, which leads to tin perovskite films essentially free from tin(IV) impurities.