In situ study of the film formation mechanism of organic–inorganic hybrid perovskite solar cells: controlling the solvate phase using an additive system

As a coating method compatible with printing, one-step spin-coating is widely used for fabricating perovskite thin films. Controlling the crystal growth rate of two precursors is essential to obtain a homogeneous film morphology. However, the film formation mechanism and role of solvate systems during spin-coating have not yet been clearly revealed. In this work, we implemented the in situ grazing incidence wide-angle X-ray scattering of CH 3 NH 3 PbI 3 perovskite material based on various additive systems to adjust the unbalanced crystal growth rate of CH 3 NH 3 I and PbI 2 . As we expected, the behavior of the solvate phase was strikingly mediated by various additives, and one of the additives greatly slowed the PbI 2 solvate phase, thus overcoming the imbalance in the crystal growth rate. Consequently, the well-controlled perovskite films have both good film morphology and high photovoltaic performance with excellent reproducibility.