Abstract
Multiscale cation inhomogeneity has been a major hurdle in state-of-the-art formamidinium–caesium (FA–Cs) mixed-cation perovskites for achieving perovskite solar cells with optimal power conversion efficiencies and durability. Although the field has attempted to homogenize the overall distributions of FA–Cs in perovskite films from both plan and cross-sectional views, our understanding of grain-to-grain cation inhomogeneity and ability to tailor it—that is, spatially resolving the FA–Cs compositional difference between individual grains down to the nanoscale—are lacking. Here we reveal that as fundamental building blocks of a perovskite film, individual grains exhibit cationic compositions deviating from the prescribed ideal composition, severely limiting the interfacial optoelectronic properties and perovskite layer durability. This performance-limiting nanoscopic factor is linked to thermodynamic-driven morphological grooving, leading to a segmented surface landscape. At the grain triple junctions, grooves form nanoscale groove traps that hinder the mixing of solid-state cations across grains and thus retard inter-grain FA–Cs mixing. By rationally modulating the heterointerfacial energies, we reduced the depth of these nanoscale groove traps by a factor of three, significantly improving cation homogeneity. Perovskite solar cells with shallower nanoscale groove traps demonstrate enhanced power conversion efficiencies (25.62%) and improved stability under various standardized international protocols. Our work highlights the significance of resolving surface nano-morphologies for homogeneous properties of perovskites.
| Original language | English |
|---|---|
| Article number | 100064 |
| Journal | Nature Nanotechnology |
| DOIs | |
| State | Accepted/In press - 2025 |
Funding
Y.Z. acknowledges the research grants from the National Natural Science Foundation of China (NSFC) Excellent Young Scientists Fund (number 52222318), the Hong Kong Research Grant Council (RGC) Early Career Scheme (number 22300221) and General Research Fund (number 12302822), the NSFC/RFC Collaborative Research Scheme (number CRS_HKUST203/23) and the start-up grant from Hong Kong University of Science and Technology (number R9901). Y.Z. also acknowledges the support from the China Merchants Group, particularly China Merchants Testing Certification International Co. Ltd. and China Merchants Research Institute of Advanced Technology Co., Ltd. for translating fundamental research to future technology innovation. J.Y. and M.A. acknowledge the funding from the US National Science Foundation (number 2043205). Y.X. acknowledges the RGC General Research Fund (number 16301720). M.H. and T.X. acknowledge the Hong Kong PhD Fellowship Scheme. T.D. acknowledges the RGC Postdoctoral Fellowship Scheme. X.Z. acknowledges the K. C. Wong Education Foundation. Cathodoluminescence microscopy was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. The work at Yale University was supported by the US National Science Foundation (number DMR-2313648). We also acknowledge the experiment assistance from C. Yang and Y. Zhang from \u03A3Lab of The Hong Kong University of Science and Technology (HKUST), S. Guo from The Hong Kong Polytechnic University and M.-G.J. from Southeast University.