Evolution of large-grained CuSbS2 thin films by rapid sulfurization of evaporated Cu–Sb precursor stacks for photovoltaics application

Ternary chalcostibite (CuSbS 2 ) is a non-toxic and earth-abundant thin-film solar cell material with an optimal band gap, high optical absorption coefficient, and p-type electrical conductivity. Large-grained CuSbS 2 thin films are crystallized by sulfurizing thermally evaporated Cu/Sb/Cu precursor stacks at 450 °C for a short duration of 1–10 min. The precursor stacks sulfurized at 450 °C for 1 min resulted in the formation of a Cu-deficient (to a small extent) and Sb-rich large-grained thin-films of CuSbS 2 without any secondary phases. Increasing the sulfurization duration from 5 min to 10 min resulted in the formation of near-stoichiometric CuSbS 2 films with columnar growth and more uniformly sized grains. The direct band gap of the films is found to be 1.42 eV. The electrical resistivity decreases from 28.6 to 16.7 Ω cm upon increasing the sulfurization duration from 1 to 10 min, respectively, and the hole mobility is in the range of 0.44–0.56 cm 2 V −1 s −1 . The solar cells fabricated using the CuSbS 2 films sulfurized for a duration of 5 min exhibited a maximum power conversion efficiency of 2.5% with an open-circuit voltage of 568.7 mV and a short-circuit current density of 13.8 mA/cm 2 . This study provides a pathway for the development of high-efficiency CuSbS 2 solar cells.