Record open-circuit voltage of 0.85 V via indium-content engineering in efficient CuInS2 solar cells

CuInS 2 is a promising light-harvesting material for solar cells due to its long-term stability, suitable bandgap and favorable optical absorption coefficient. Here, solar cells with In-rich CuInS 2 light-active layer are fabricated by increasing the feed ratio in precursor solution. The CuAu phases within chalcopyrite CuInS 2 films are inhibited with increased In molar ratio, leading to a better quality of CuInS 2 films as well as reduction in charge recombination centers in solar cells. Moreover, the band alignment of CuInS 2 /Spiro-OMeTAD interface is adjusted by increased In molar ratio, and the charge carriers are effectively separated at the CuInS 2 /Spiro-OMeTAD interface due to the lower valence band level of In-rich CuInS 2 films. These improvements result in a planar CuInS 2 solar cell with an efficiency of 7.66% and an open-circuit voltage reached 0.85 V. The In-rich CuInS 2 devices exhibit the lower voltage loss, which enhances the potential for high-efficiency solar cells.