Reducing exciton binding energy of antimony-based perovskites by improving the phase purity for efficient solar cells.

Antimony-based halide perovskites have attracted significant attention owing 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 Cs₃Sb₂Cl_xI_9-x films. An optimized content of excess SbI₃ in the precursor composition was found to effectively suppress the CsI impurity phases in the obtained Cs₃Sb₂Cl_xI_9-x films, leading to enhanced crystallinity and reduced defects. Furthermore, the obtained Cs₃Sb₂Cl_xI_9-x films exhibited an increased dielectric response and reduced exciton binding energy, which are conducive to exciton dissociation and carrier transport. A champion efficiency of 3.42% was achieved with the optimized solar cell devices, which is one of the highest efficiencies reported for all-inorganic antimony-based PSCs. These findings provide new perspectives for exploring high-efficiency antimony-based PSCs.