Regulating charge carrier extraction and transport with dual-interface modification for efficient perovskite solar cells

Planar-structured metal halide perovskite solar cells (PSCs) have received considerable attention thanks to their superior optoelectronic properties with a record power conversion efficiency (PCE) of over 25%. However, further improvements in the PCE of these devices are still limited fundamentally by excessive charge carrier recombination, due to the prevailing defects in perovskites and their adjacent interfaces to the charge transport layer (CTL). Herein, we report an efficient dual-interface modification strategy to improve the charge carrier management in both perovskites and perovskite/CTL interfaces by post-treatment of perovskite surfaces with GABr and introducing NH4F-treated SnO2 as an electron transport layer, respectively. Accordingly, suppressed structural defects, improved crystallinity of the perovskite, and reduced interfacial defects have been achieved simultaneously, thus facilitating the carrier transport and extraction. As a result, the target PSCs attain a decent PCE of 19.61% with a remarkably enhanced fill factor of 78.34%. Moreover, the underlying mechanism concerning these improvements has been proposed. The present findings might provide some meaningful insights into exploring high-performance PSCs toward theoretically limited efficiency.