Controlled growth of CH3NH3PbI3 films towards efficient perovskite solar cells by varied-stoichiometric intermediate adduct

Lewis acid-base adduct approach with anti-solvent (diethyl ether) has been one of the efficient strategies to prepare high-quality perovskite films for top-performing perovskite solar cells. Conventionally, the molar ratio of CH3NH3I:PbI2:DMSO in the precursor solution is 1:1:1, however, DMSO will be volatile alongside the extraction of DMF due to its miscibility with DMF solvent during the process of anti-solvent washing, which introduces a non-stoichiometric intermediate adduct CH3NH3I·PbI2·xDMSO (x < 1). In this work, we increased the DMSO content in the Lewis acid-base adduct approach to enhance the conversion efficiency of perovskite solar cells. More complete intermediate adduct CH3NH3I·PbI2·DMSO and wider window period of washing process ensure high-quality perovskite films and high reproducibility with raised content of DMSO. Furthermore, the devices prepared by the precursor solution of CH3NH3I:PbI2:xDMSO (x = 2.0) exhibit high reproducibility and the best efficiency of perovskite solar cells is 17.84% under one-sun illumination.