Bonding-Enabled Interfacial Reconstruction at Buried Interface for High-Efficiency Sb₂Se₃ Solar Cells

Antimony selenide (Sb₂Se₃) 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 Sb₂Se₃ 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/Sb₂Se₃ interface. We found that HCl post-treatment on the CdS film can effectively enhance interfacial uniformity and reduce residual SO₄ ^2- species on the (100) facet of CdS. These surface characteristics facilitate the formation of Sb-S bonding at the CdS/Sb₂Se₃ interface, thereby promoting bonding-mediated oriented growth of Sb₂Se₃. Consequently, the deposited Sb₂Se₃ 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 Sb₂Se₃ 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.