Fe Single Atom Catalysts Promoting Polysulfide Redox Reduction in Quantum Dot Photovoltaics
Linna Li, Yu Lin, Yongming Xia, Di Lin, Yang Xiang, Jiaqi Fang, Xuehui Liu, Jiawen Chen, Xiong Yin, Chenyan Ma, Xiaoying Yan, Peng Xu, Rui Xu, Lipeng Zhang, Zhihai Cheng, Leyu Wang
Abstract
Developing cost-effective and highly efficient photocathodes toward polysulfide redox reduction is highly desirable for advanced quantum dot (QD) photovoltaics. Herein, we demonstrate nitrogen doped carbon (N-C) shell-supported iron single atom catalysts (Fe-SACs) capable of catalyzing polysulfide reduction in QD photovoltaics for the first time. Specifically, Fe-SACs with FeN 4 active sites feature a power conversion efficiency of 13.7% for ZnCuInSe-QD photovoltaics (AM1.5G, 100 mW/cm 2 ), which is the highest value for ZnCuInSe QD-based photovoltaics, outperforming those of Cu-SACs and N-C catalysts. Compared with N-C, Fe-SACs exhibit suitable energy level matching with polysulfide redox couples, revealed by the Kelvin probe force microscope, which accelerates the charge transferring at the interfaces of catalyst/polysulfide redox couple. Density functional theory calculations demonstrate that the outstanding catalytic activity of Fe-SACs originates from the preferable adsorption of S 4 2– on the FeN 4 active sites and the high activation degree of the S–S bonds in S 4 2– initiated by the FeN 4 active sites.