Interfacial engineering of oxygenated chemical bath–deposited CdS window layer for highly efficient Sb₂Se₃ thin-film solar cells

Antimony chalcogenides with quasi-one-dimensional nanoribbon structures represent a new group of cost-effective, non-toxic, and earth-abundant materials for photovoltaics. In this work, interfacial engineering of oxygenated chemical bath–deposited (CBD) CdS buffer layers were used to tailor Sb₂Se₃ thin-film solar cells using close space sublimation (CSS) deposition process. Sb₂Se₃ solar cells with oxygenated CBD CdS have demonstrated a champion power conversion efficiency of 6.3% with graphite as back contact. Van der Waals (vdW) gap in Sb₂Se₃ is regulated via oxygen diffusion, which significantly influences the growth direction of (Sb₄Se₆)_n quasi-one-dimensional nanoribbons. The improved interface quality and ribbon orientation, in turn, enhance the electrical and optical properties as well as device performance of the Sb₂Se₃ solar cells. The defect level and corresponding device performance associated with the oxygen environment were investigated by both theoretical and experimental approaches. This work provides an effective way to tune the microstructure and electronic structure of non-cubic chalcogenides by tailoring the interfacial area between the window layer and Sb₂Se₃ absorber.