Suppression of the interface-dependent nonradiative recombination by using 2-methylbenzimidazole as interlayer for highly efficient and stable perovskite solar cells

Despite the tremendous progress in the efficiency of perovsite solar cells (PSCs), nonradiative recombination losses, mainly associated with the interfacial defects, still remain as a challenge that hinders their commercialization. In this study, we report a facile interface engineering strategy for highly-efficient planar PSCs by employing in a series concentration of 2-methylbenzimidazole (MBIm) between SnO2 electron transporting layer (ETL) and photoactive perovskite layer. The preliminary results demonstrate that MBIm molecules reduce the band-offset and enlarge the built-in potential (Vbi) between perovskite and SnO2, resulting in a lower photovoltage loss. Besides, MBIm provides an efficient passivation by donating the lone pair electrons to the uncoordinated Pb2+ ions in perovskite structure through the formation of Lewis adducts, thereby minimizing nonradiative recombination in the ensuing devices. As a result, a remarkable increase in the efficiency from 19.5% (pristine cell) to 21.6% (3 mM-MBIm modified cell) was achieved with a dramatic increase in Voc (similar to 90 mV). Meanwhile, an admissible improvement in long-term stability was obtained by retaining similar to 85 and 90% of initial performance under high humidity and continuous light soaking conditions, respectively. The prolonged stability is ascribed to the formation of compact and high-quality perovskite layer deposited on the modified surfaces. We believe that this study offers an efficient strategy by minimizing the nonradiative recombination losses through ETL/perovskite interface for high-efficiency and stable perovskite cells.