Fabricating α-FAPbI<sub>3</sub> Perovskite Photovoltaics in Ambient Air by DMSO Extraction
Yan Liu, Bin Ding, Yong Ding, Gao Zhang, Xin Zhang, Xintong Ma, Yao Wang, Lirong Zeng, Meijun Liu, Guan‐Jun Yang, Mohammad Khaja Nazeeruddin, Bo Chen
Abstract
Formamidinium lead iodide (FAPbI 3 ) stands out as a promising composition for perovskite solar cells. However, achieving a pure α-FAPbI 3 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-FAPbI 3 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 FAPbI 3 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-FAPbI 3 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.