Reducing Exciton Binding Energy of Antimony-based Perovskites via Improving Phase Purity for Efficient Solar Cells

Abstract

Antimony-based halide perovskites have attracted growing attention due to their unique optoelectronic properties and low toxicity. However, the distinct defect physics and high exciton binding energy of antimony-based perovskites compared with their lead-based analogues significantly hinder the photovoltaic performance of antimony-based perovskite solar cells (PSCs). In this work, a feasible strategy by regulating the precursor composition is introduced to mitigate the defects and impurity phases of Cs3Sb2ClxI9-x films. An optimized content of excess SbI3 in the precursor composition is found to effectively suppress the CsI impurity phases in the obtained Cs3Sb2ClxI9-x films, leading to enhanced crystallinity and reduced defects. Furthermore, the obtained Cs3Sb2ClxI9-x films exhibit increased dielectric response and reduced exciton binding energy, which is conducive to exciton dissociation and carrier transport. A champion efficiency of 3.42% is achieved with the optimized solar cell devices, which is one of the highest efficiencies for all inorganic antimony-based PSCs. These findings provide new perspectives for exploring high-efficiency antimony -based PSCs.