Research on the Influence of the Interfacial Properties Between a Cu₃BiS₃ Film and an In_xCd_1−xS Buffer Layer for Photoelectrochemical Water Splitting

The ternary compound photovoltaic semiconductor Cu₃BiS₃ thin film-based photoelectrode demonstrates a quite promising potential for photoelectrochemical hydrogen evolution. The presented high onset potential of 0.9 V_RHE attracts much attention and shows that the Cu₃BiS₃ thin films are quite good as an efficient solar water splitting photoelectrode. However, the CdS buffer does not fit the Cu₃BiS₃ thin film: the conduction band offset between CdS and Cu₃BiS₃ reaches 0.7 eV, and such a high conduction band offset (CBO) significantly increases the interfacial recombination ratio and is the main reason for the relatively low photocurrent of the Cu₃BiS₃/CdS photoelectrode. In this study, the In_xCd_1−xS buffer layer is found to be significantly lowered the CBO of CBS/buffer and that the In incorporation ratio of the buffer influences the CBO value of the CBS/buffer. The Pt-TiO₂/In_0.6Cd_0.4S/Cu₃BiS₃ photocathode exhibits an appreciable photocurrent density of ≈12.20 mA cm⁻² at 0 V_RHE with onset potential of more than 0.9 V_RHE, and the ABPE of the Cu₃BiS₃-based photocathode reaches the highest value of 3.13%. By application of the In_0.6Cd_0.4S buffer, the Cu₃BiS₃-BiVO₄ tandem cell presents a stable and excellent unbiased STH of 2.57% for over 100 h.