Bonding‐Enabled Interfacial Reconstruction at Buried Interface for High‐Efficiency Sb ₂ Se ₃ Solar Cells

ABSTRACT Antimony selenide (Sb ₂ Se ₃ ) has attracted intense attention as one of the most promising photovoltaic materials, owing to its outstanding optoelectronic properties and thermal and chemical stability. However, the solar cells based on Sb ₂ Se ₃ suffer from inferior interfacial contact and severe recombination loss at the buried interface, which limits the efficiency improvement of the device. To overcome these limitations, here we develop an acid‐activated interfacial reconstruction strategy to improve the quality of the buried CdS/Sb ₂ Se ₃ interface. We found that HCl post‐treatment on the CdS film can effectively enhance interfacial uniformity and reduce residual SO ₄ ²⁻ species on the (100) facet of CdS. These surface characteristics facilitate the formation of Sb‐S bonding at the CdS/Sb ₂ Se ₃ interface, thereby promoting bonding‐mediated oriented growth of Sb ₂ Se ₃ . Consequently, the deposited Sb ₂ Se ₃ exhibits a preferred [hk1] orientation and mitigated Se vacancy defects, leading to enhanced carrier transport efficiency and suppressed non‐radiative recombination loss in the device. Ultimately, we achieved a champion power conversion efficiency (PCE) of 9.74% in Sb ₂ Se ₃ superstrate solar cells fabricated via thermal evaporation (TE). This approach establishes a novel paradigm for interfacial engineering, where the in situ activation of CdS surfaces enhances interfacial properties and facilitates chemical bonding during subsequent deposition.