In situ growth of Z-scheme CuS/CuSCN heterojunction to passivate surface defects and enhance charge transport

Abstract Copper thiocyanate (CuSCN) has been considered as a promising hole transport material (HTMs), attributing to its inherent stability, low-cost, and suitable energy levels. To make it more attractive in practical applications, the drawbacks of CuSCN in poor charge transport and serious defect recombination are bottlenecks that need to be overcome. In this work, we propose an effective strategy of in-situ decorating CuSCN with copper sulfide quantum dots (CuS QDs), a simple one-step electrochemical deposition process, to solve these issues. Compared with the pristine CuSCN, the constructed Z-Scheme heterojunction of CuS QDs/CuSCN can significantly promote charge transport and restrict recombination. In addition, the decorated CuS QDs can not only passivate defects of CuSCN, but also provide more contacting sites to facilitate hole injection when employing as HTM. As a result, the average bulk charge lifetime was improved from 0.37 ms to 0.47 ms, and the surface recombination rate constant was suppressed. We believe that the excellent performances will pave it toward practical device applications, including solar cells, photocatalysis, photoelectrochemical sensors, and light-emitting diodes.