Efficiency Improvement of Sb₂Se₃ Solar Cells via Grain Boundary Inversion

Sb2Se3 is a promising low-cost and low-toxicity photovoltaic material. Recent research revealed that recombination losses in the absorber limited the efficiency of Sb2Se3 solar cells. Herein we demonstrated a strategy of grain boundary (GB) inversion to alleviate such recombination loss. Owning to its one-dimensional crystal structure, we successfully inverted the GBs of Sb2Se3 films by introducing n-type Cu interstitial doping at GBs via low-temperature CuCl2 treatment. A built-in electric field is established between p-type grain interiors and n-type GBs, which spatially separates phototogerated carriers, suppresses recombination, and enhances carrier collection. Finally, we obtained an efficiency of 7.04%, which is the highest efficiency of Sb2Se3 solar cells based on rapid thermal evaporation technology. We envision that this GB inversion strategy is generally applicable to Sb2Se3 solar cells with different device configuration or produced from other methods and is extendable to other emerging low-dimensional solar cells.