Efficient and Stable Inverted Perovskite Solar Cells Enabled by Inhibiting Voids via a Green Additive

The buried interface in inverted perovskite solar cells (PSCs) is critical for determining device performance. However, during annealing, the perovskite crystallized downward from the film's top surfaces, and the use of dimethyl sulfoxide (DMSO) often resulted in voids at the perovskite bottom surface, which negatively impacted PSC performance. In this study, a green solid-state additive, piracetam (PA), was introduced into a perovskite precursor to reduce void formation. Due to the stronger interaction with perovskite components than DMSO, nonvolatile PA could remain within the perovskite films during thermal annealing to avoid volume collapse, thereby preventing the formation of voids at the buried interface as well as passivating the defects of undercoordinated Pb²⁺. Additionally, the introduction of PA could effectively enhance the crystallization of perovskite, leading to an improved quality of the perovskite films and depressed nonradiative recombination. As a result, the power conversion efficiency (PCE) of PSCs increased significantly from 20.95 to 23.42% with excellent operational and thermal stability.