CH₃NH₃Cl-Assisted One-Step Solution Growth of CH₃NH₃PbI₃: Structure, Charge-Carrier Dynamics, and Photovoltaic Properties of Perovskite Solar Cells

We demonstrate a novel one-step solution approach to prepare perovskite CH3NH3PbI3 films by adding CH3NH3Cl (or MACl) to the standard CH3NH3PbI3 precursor (equimolar mixture of CH3NH3I and PbI2) solution. The use of MACl strongly affects the crystallization process of forming pure CH3NH3PbI3, leading not only to enhanced absorption of CH3NH3PbI3 but also to significantly improved coverage of CH3NH3PbI3 on a planar substrate. Compared to the standard one-step solution approach for CH3NH3PbI3, using MACl improves the performance of CH3NH3PbI3 solar cells from about 2% to 12% for the planar cell structure and from about 8% to 10% for the mesostructured device architecture. Although we find no significant effect of using MACl on charge transport and recombination in mesostructured perovskite cells, the recombination resistance for planar cells increases by 1–2 orders of magnitude by using MACl. These results suggest that this new one-step solution approach is promising for controlling CH3NH3PbI3 growth to achieve high-performance perovskite solar cells.