Fabricating α-FAPbI3 Perovskite Photovoltaics in Ambient Air by DMSO Extraction

Formamidinium lead iodide (FAPbI3) stands out as a promising composition for perovskite solar cells. However, achieving a pure α-FAPbI3 film typically requires a dry environment, which poses a challenge for its widespread commercial application. Our investigation reveals that an excessive presence of dimethyl sulfoxide (DMSO) in the intermediate film obstructs the formation of a pure α-FAPbI3 perovskite film under ambient air. This occurs because DMSO induces instability of intermediates, provokes an unfavorable α-to-δ phase transition, and leaves behind a residual δ-phase in the annealed FAPbI3 film. We discover that there exists a competition between DMSO and MACl regarding the stabilization of the α-phase perovskite structure. A DMSO extraction strategy is proposed to release the beneficial effect of MACl on α-phase stabilization, facilitating the deposition of void-free, pure α-FAPbI3 perovskite films with a low defect density in ambient air. Consequently, this breakthrough enables the fabrication of perovskite solar cells and modules exhibiting impressive efficiencies of 25.71% and 22.12%, respectively.