Surface Reconstruction Drives Highly Efficient Carrier Management in Antimony Selenosulfide Solar Cells

Antimony selenosulfide (Sb₂(S,Se)₃) solar cells have emerged as promising photovoltaic technology. However, the photovoltaic performance of Sb₂(S,Se)₃ solar cells fabricated using chemical bath deposition (CBD) still faces a major bottleneck in carrier loss, with efficiencies remaining below 10%. Here, based on the Sb₂(S,Se)₃ absorber layer prepared from CBD, we propose a surface reconstruction (SR) strategy in which an amorphous Sb₂S₃ layer is additionally deposited onto the surface of the amorphous Sb₂(S,Se)₃ layer, followed by postannealing treatment to promote anion interdiffusion. This absorber exhibits a gradient bandgap structure, effectively enhancing bulk carrier transport and further improving the interface characteristics of the Sb₂(S,Se)₃/hole transport layer heterojunction. These benefits significantly reduce the carrier transport loss from 11.06% to 8.5% and help in achieving a champion efficiency of 10.02%, which is the highest efficiency reported so far for the CBD-processed Sb₂(S,Se)₃ solar cells. This work not only demonstrates the SR as an effective post-treatment strategy but also paves the way toward high-performance optoelectronic devices.