Defect Control for High-Efficiency Cu2ZnSn(S,Se)4 Solar Cells by Atomic Layer Deposition of Al2O3 on Precursor Film

Cu 2 ZnSn(S,Se) 4 are emerging as promising photovoltaic materials due to their outstanding photoelectrical performances, benign grain boundaries, and Earth-abundant constituent elements. However, there are largely distributed cation-disordering defects and defect clusters, which lead to an increase in recombination and a large open-circuit voltage deficit and thus deteriorate device performance. Herein, defect control for a high-efficiency Cu 2 ZnSn(S,Se) 4 solar cell by atomic layer deposition of aluminum oxide (ALD-Al 2 O 3 ) on the precursor film is reporter. Cu Zn defects and Sn-related deep defects are largely suppressed because of the decrease in Sn 2+ and the increase in Sn 4+ in the film by ALD-Al 2 O 3 on the precursor are found, and the crystallinity of absorber layer is improved from a double-layer structure to a completely single-layer structure. Furthermore, the carrier lifetime and recombination in the bulk and interface are significantly improved for devices with ultrathin Al 2 O 3 . Using this approach, the conversion efficiency increases from 8.8% to 11.0% and the open-circuit voltage deficit decreases from 0.621 to 0.577 V. Herein, a deep understanding of the relationship between Al 2 O 3 incorporation and high-efficiency Cu 2 ZnSn(S,Se) 4 devices and a new direction for controlling defects to further improve the performance of kesterite solar cells are provided.