Photoexcitation-induced passivation of SnO₂ thin film for efficient perovskite solar cells

A high-quality tin oxide electron transport layer (ETL) is a key common factor to achieve high-performance perovskite solar cells (PSCs). However, the conventional annealing technique to prepare high-quality ETLs by continuous heating under near-equilibrium conditions requires high temperatures and a long fabrication time. Alternatively, we present a non-equilibrium, photoexcitation-induced passivation technique that uses multiple ultrashort laser pulses. The ultrafast photoexcitation and following electron-electron and electron-phonon scattering processes induce ultrafast annealing to efficiently passivate surface and bulk defects, and improve the crystallinity of SnO₂, resulting in suppressing the carrier recombination and facilitating the charge transport between the ETL and perovskite interface. By rapidly scanning the laser beam, the annealing time is reduced to several minutes, which is much more efficient compared with conventional thermal annealing. To demonstrate the university and scalability of this technique, typical antisolvent and antisolvent-free processed hybrid organic-inorganic metal halide PSCs have been fabricated and achieved the power conversion efficiency (PCE) of 24.14% and 22.75% respectively, and a 12-square-centimeter module antisolvent-free processed perovskite solar module achieves a PCE of 20.26%, with significantly enhanced performance both in PCE and stability. This study establishes a new approach towards the commercialization of efficient low-temperature manufacturing of PSCs.