Managed spatial strain uniformity for efficient perovskite photovoltaics enables minimized energy deficit

Although X-ray diffraction (XRD) technology has played an essential role in studying the lattice strain of perovskite solar cells (PSCs), accurate construction of the relationship between strains and PSC performance remains challenging due to its limitations. This study investigates the spatial strain distributions of perovskite films on electron transport layers (ETLs) with different surface free energies (γss) through confocal micro-Raman spectroscopy (CMRS) mapping and XRD technology. Results showed that CMRS mapping could more effectively reflect the distribution and size of spatial strain. Uniformed spatial strain with larger grain and preferred orientations can be realized over substrates with optimized γs, corresponding to recombination suppression and interfacial carrier extraction enhancement and significantly reducing open-circuit voltage (VOC) deficits. Optimized PSCs achieve the power conversion efficiency (PCE) of 24.64% and demonstrate excellent compatibility toward large-area or flexible applications, with 20.66% and 22.13% PCEs based on perovskite mini-module and flexible PSCs, respectively.