Intermediate Phase Intermolecular Exchange Triggered Defect Elimination in CH₃NH₃PbI₃ toward Room-Temperature...

The solvent-engineered one-step spin-coating method has been widely used to produce full-coverage CH₃NH₃PbI₃ films for perovskite solar cells by forming an intermediate phase. However, the resultant CH₃NH₃PbI₃ films usually contain numerous structural and compositional defects mainly resulting from the fast crystallization of the intermediate phase as well as the escape of CH₃NH₃I species induced by the inevitably thermal annealing recipe. Herein, a facile room-temperature intermolecular exchange route is proposed to enable conversion of the intermediate phase into uniform and ultra-flat CH₃NH₃PbI₃ films. It can effectively inhibit the formation of structural and compositional defects in the resultant films, and even repair their inherent defects. As a result, the efficiency of perovskite solar cells can be boosted to 19.45% with a stabilized value of 18.55%, which is much higher than that from the ones fabricated by thermal annealing. This study suggests a facile and low-cost route to room-temperature fabrication of highly efficient perovskite solar cells including flexible ones.