Thermal-Induced Volmer–Weber Growth Behavior for Planar Heterojunction Perovskites Solar Cells

Recently, a hot casting technique was developed to prepare pinhole free perovskite thin films with millimeter-scale grains. However, its intrinsic formation mechanism has not been studied in the literature up to now. Here, we demonstrate a Volmer–Weber growth mechanism during the hot casting, a process that typically involves the formation of island shaped grains and the following integration into dense perovskite films. It was found that such crystal growth was determined by the multiple effect of thermal energy and force centrifugal field. Particularly, the thermal energy can facilitate the formation of CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> and overcome the energy barriers of the precursor solutions on the substrates. The detailed morphologies of CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> films can be optimized by regulating deposition parameters including casting temperature and rotate speed. Solar cells constructed with these thin films achieve an average power conversion efficiency of 12.6 ± 0.3% under standard AM 1.5 G conditions.