Thin-film solar cells based on hybrid lead halide perovskites have achieved certified power conversion efficiencies exceeding 24%, approaching those of crystalline silicon. This motivates deeper studies of the mechanisms that determine their performance. Twin defect sites have been proposed as a source of traps in perovskites, yet their origin and influence on photovoltaic performance remain unclear. It is found that twin defects-observed herein via both transmission electron microscopy and X-ray diffraction-are correlated with the amount of antisolvent added to the perovskite and that twin defects in the highest-performing perovskite photovoltaics are suppressed. Heterogeneous supersaturation nucleation is discussed as a contributor to efficient perovskite-based optoelectronic devices. ; The authors thank the Ministry of Science and Technology of Taiwan for support of this research (MOST 106‐2917‐I‐564‐007 and MOST 107‐2221‐E‐007‐055‐MY3). This publication is based in part on work supported by the US Department of the Navy, Office of Naval Research (Grant Award No. N00014‐17‐1‐2524), the Ontario Research Fund – Research Excellence Program, and the Natural Sciences and Engineering Research Council (NSERC) of Canada. M.I.S. acknowledges the support of the Banting Postdoctoral Fellowship Program, administered by the Government of Canada.
Copper-based materials are promising electrocatalysts for CO2 reduction. Prior studies show that the mixture of copper (I) and copper (0) at the catalyst surface enhances multi-carbon products from CO2 reduction; however, the stable presence of copper (I) remains the subject of debate. Here we report a copper on copper (I) composite that stabilizes copper (I) during CO2 reduction through the use of copper nitride as an underlying copper (I) species. We synthesize a copper-on-nitride catalyst that exhibits a Faradaic efficiency of 64 ± 2% for C2+ products. We achieve a 40-fold enhancement in the ratio of C2+ to the competing CH4 compared to the case of pure copper. We further show that the copper-on-nitride catalyst performs stable CO2 reduction over 30 h. Mechanistic studies suggest that the use of copper nitride contributes to reducing the CO dimerization energy barrier-a rate-limiting step in CO2 reduction to multi-carbon products. ; This work was supported financially by the Ontario Research Fund Research-Excellence Program, the Natural Sciences and Engineering Research Council (NSERC) of Canada, and the CIFAR Bio-Inspired Solar Energy program. Computations were performed on the SOSCIP Consortium's Blue Gene/Q computing platform. SOSCIP is funded by the Federal Economic Development Agency of Southern Ontario, the Province of Ontario, IBM Canada Ltd., Ontario Centres of Excellence, Mitacs and 15 Ontario academic member institutions. X-ray absorption spectra were performed on SXRMB beamlines at the Canadian Light Source (CLS), which is supported by the Canada Foundation for Innovation, Natural Sciences and Engineering Research Council of Canada, the University of Saskatchewan, the Government of Saskatchewan, Western Economic Diversification Canada, the National Research Council Canada, and the Canadian Institutes of Health Research. Z.L. acknowledges a scholarship from the China Scholarship Council (CSC) (201607090041) and Basic and Innovation Program, Beijing Jiaotong University (KSJB17016536). A.S. acknowledges Fonds de Recherche du Quebec-Nature et Technologies (FRQNT) for the postdoctoral fellowship award. P.D.L. acknowledges support from NSERC in the form of the Canada Graduate Scholarship. H.T. acknowledges the Netherlands Organisation for Scientific Research (NWO) for a Rubicon grant (680-50-1511) to support his postdoctoral research at University of Toronto. The authors thank C. Q. Zou, M. X. Liu, F. F. Fan, J. Xing and L. Gao from University of Toronto for fruitful discussions.
