Interface Engineering via Sputtered Oxygenated CdS:O Window Layer for Highly Efficient Sb2Se3 Thin‐Film Solar Cells with Efficiency Above 7%

Abstract

Antimony chalcogenide Sb2Se3 is an emerging photovoltaic absorber due to its appropriate bandgap (≈1.1 eV), high absorption coefficient (>105 cm−1), suitable p‐type conductivity, low toxicity, earth abundance, and excellent stability. However, the stringent growth condition and low photovoltage limit its power conversion efficiency (PCE). Herein, via a combined theoretical and experimental study, interface engineering via an oxygenated cadmium sulfide (CdS) window layer (CdS:O) is found to be an effective approach to improve the device performance of CdS:O/Sb2Se3 solar cells. The sputtered oxygenated CdS:O window layer can be used to replace conventional chemical‐bath‐deposited CdS window layer in the Sb2Se3 devices. The best PCE of 7.01% is demonstrated in the superstrate configuration of fluorine‐doped SnO2/CdS:O/Sb2Se3/graphite with a high open‐circuit voltage of 0.432 V, where Sb2Se3 is fabricated using the close space sublimation technique. The interfacial diffusion between Sb2Se3 and sputtered CdS:O is significantly suppressed by introducing oxygen at the interface, which prevents Cd diffusion and the formation of Cd interstitials. Combined device physics characterizations and theoretical calculations reveal that oxygen in the CdS:O/Sb2Se3 interface can increase depletion region, built‐in voltage, and reduce interfacial recombination. These findings provide the guidance to optimize quasi‐one‐dimensional non‐cubic earth‐abundant chalcogenide photovoltaic devices through interface engineering.