A potential alternative deposition technology for CdS buffer layer in kesterite solar cells via intermittent photochemical deposition

Abstract In this work, we have developed a novel intermittent photochemical deposition (IPCD) method to prepare CdS buffer layer on Cu2ZnSn(S,Se)4 (CZTSSe) absorber. Results show that the optimized IPCD-CdS buffer layer is compact and uniform, ensuring a perfect contact with the CZTSSe absorber. Our experiments confirm that CdS can nucleate and grow on conducting substrates via IPCD method with controllable particle sizes. Based on the analyses, an electron assisted deposition mechanism is proposed to give a comprehensive insight into the IPCD process. Furthermore, the assembled CZTSSe solar cells with CdS layers deposited via IPCD deliver a highest photoelectric conversion efficiency (PCE) of 5.82%, which is improved by 22% compared to the ones with CdS layers via continuous PCD. Further analyses suggest that the efficiency improvement could be attributed to the improved band alignment at the heterojunction interface between CdS and CZTSSe layers. Our research provides a new way to improve the PCE for CZTSSe based solar cells via optimized deposition process.