Efficient\nand Stable\nInverted Perovskite Solar Cells\nEnabled by Inhibiting Voids via a Green Additive

The buried interface in inverted\nperovskite solar cells\n(PSCs)\nis critical for determining device performance. However, during annealing,\nthe perovskite crystallized downward from the film’s top surfaces,\nand the use of dimethyl sulfoxide (DMSO) often resulted in voids at\nthe perovskite bottom surface, which negatively impacted PSC performance.\nIn this study, a green solid-state additive, piracetam (PA), was introduced\ninto a perovskite precursor to reduce void formation. Due to the stronger\ninteraction with perovskite components than DMSO, nonvolatile PA could\nremain within the perovskite films during thermal annealing to avoid\nvolume collapse, thereby preventing the formation of voids at the\nburied interface as well as passivating the defects of undercoordinated\nPb<sup>2+</sup>. Additionally, the introduction of PA could effectively\nenhance the crystallization of perovskite, leading to an improved\nquality of the perovskite films and depressed nonradiative recombination.\nAs a result, the power conversion efficiency (PCE) of PSCs increased\nsignificantly from 20.95 to 23.42% with excellent operational and\nthermal stability.