Solution-Processed CuSbS₂ Thin Films and Superstrate Solar Cells with CdS/In₂S₃ Buffer Layers

Herein, we describe a method to deposit thin films of the semiconductor CuSbS₂ with micrometer-sized grains under inert atmosphere at mild processing temperatures. This is achieved through the decomposition of Cu and Sb dithiocarbamate precursors. Through careful optimization of the processing conditions, phase-pure p-type CuSbS₂ thin films with high photoconductivity have been achieved. Tunability of the Cu/Sb ratios is also demonstrated while maintaining phase purity. Photoelectrochemistry is conducted as a function of both processing temperature and Cu/Sb ratio with 10% copper-deficient films annealed between 350 and 400 °C, producing the highest relative photocurrent. To assess the performance of these thin films, planar thin-film solar cells are fabricated. Superstrate solar cells (glass/FTO/CdS/(In₂S₃)/CuSbS₂/SPIRO/Au) with either a CdS n-type window layer or a CdS/In₂S₃ dual n-type window/buffer layer are investigated. The use of a thin buffer layer further boosts the overall device performance, and a champion power conversion efficiency of 1.72% is demonstrated. To date, this efficiency is among the best reported for CuSbS₂ solar cells and the highest for solution-processed devices using a planar thin-film architecture.