Controllable intermediates by molecular self-assembly for optimizing the fabrication of large-grain perovskite films via one-step spin-coating

Abstract

Abstract In the past two years, the introduction of dimethylsulfoxide (DMSO) has recognized as an effective way to prepare high-quality pervoskite films. During the developed DMSO process, the formation of an intermediate phase has proven to uniform crystal growth rates between CH 3 NH 3 I (MAI) and PbI 2 in common solvents. In this work, controllable intermediates were obtained in dimethylformamide (DMF) by additional solvent of DMSO, which tend to be closely packed by means of intermolecular self-assembly. In addition, the bond strength and chemical composition of intermediate phase were investigated with FTIR and TGA. The use of different ratios of DMSO leads to four different complexes of MAI·PbI 2 ·DMF and MAI·PbI 2 ·(DMSO) y (y = 0.6, 1.5, 1.9), thus dramatically influencing the crystallization of perovskite films. Of these complexes, optimized MAI·PbI 2 ·(DMSO) 1.5 intermediate adduct enables highly dense perovskite thin films with large grain size and enhances efficient perovskite solar cells with high charge carrier lifetime.