Reveal the growth mechanism in perovskite films via weakly coordinating solvent annealing

Abstract

In this study, we investigated the nucleation mechanism of perovskite films by employing isopropanol (IPA), a weakly coordinating solvent, to anneal both PbI2 and CH3NH3PbI3 in the sequential deposition and CsPbI3 in the one-step deposition. IPA solvent annealing (IPA SA) of PbI2 films was carried out at different temperatures. The grain size, compactness, roughness and morphology of PbI2 and CH3NH3PbI3 films were seriously affected by annealing methods. Similarly, weakly coordinating solvent annealing process was also employed to anneal all inorganic CsPbI3 perovskite in a one-step method. A continuous and dense CsPbI3 film with uniform grain size was obtained. We recognized that weakly coordinating solvent annealing for perovskite could regulate the dissolution-recrystallization process via controlling the volume of residual solvent in perovskite intermediate films. The power conversion efficiency (PCE) of conventional CH3NH3PbI3 perovskite solar cells (PSCs) reached 17.4% and that of CsPbI3 PSCs reached 2.5% based on this sequential IPA SA process.