Hydrazine Hydrate-Induced Surface Modification of CdS Electron Transport Layer Enables 10.30%-Efficient Sb 2 (S,Se) 3 Planar Solar Cells.

Antimony selenosulfide (Sb 2 (S,Se) 3 ), a simple alloyed compound containing earth-abundant constituents, with a tunable bandgap and high absorption coefficient has attracted significant attention in high-efficiency photovoltaic applications. Optimizing interfacial defects and absorber layers to a high standard is essential in improving the efficiency of Sb 2 (S,Se) 3 solar cells. In particular, the electron transport layer (ETL) greatly affects the final device performance of the superstrate structure. In this study, a simple and effective hydrazine hydrate (N 2 H 4 ) solution post-treatment is proposed to modify CdS ETL in order to enhance Sb 2 (S,Se) 3 solar cell efficiency. By this process, oxides and residual chlorides, caused by CdCl 2 treated CdS under a high temperature over 400 °C in air, are appropriately removed, rendering smoother and flatter CdS ETL as well as high-quality Sb 2 (S,Se) 3 thin films. Furthermore, the interfacial energy band alignment and recombination loss are both improved, resulting in an as-fabricated FTO/CdS-N 2 H 4 /Sb 2 (S,Se) 3 /spiro-OMeTAD/Au solar cell with a high PCE of 10.30%, placing it in the top tier of Sb-based solar devices. This study provides a fresh perspective on interfacial optimization and promotes the future development of antimony chalcogenide-based planar solar cells.