Controlling\nIntermediate Phase Formation to Enhance\nPhotovoltaic Performance of Inverted FA-Based Perovskite Solar Cells

Formamidinium (FA)-based perovskites exhibit significant\npotential\nfor highly efficient photovoltaics due to their promising optoelectronic\nproperties and optimal bandgap. However, the undesired inactive phase\narises from multiple crystal nucleation pathways formed by various\nintermediate phases during the film formation process, persistently\naccompanying it. FA-based perovskites frequently struggle to form\nuniform, highly crystalline films. This challenge complicates the\ndevelopment of reliable and highly reproducible crystallization processes\nfor perovskites and the establishment of guidelines for controlling\nthe α-phase formation. In this work, we investigate the role\nof poly(acrylonitril-<i>co</i>-methyl acrylate) (PAM) to\nsimultaneously control nucleation and subsequent α-phase crystallization.\nThis successfully demonstrates the regulation of oriented crystal\ngrowth through the creation of a PAM-PbI<sub>2</sub> intermediate.\nUltimately, PAM-modified p–i–n architecture devices\nobtain a promising power conversion efficiency (PCE) of 25.30%, with <i>V</i><sub>OC</sub> (1.211 V), achieving 95% of the detailed\nbalance limit. Additionally, PAM-modified devices maintain ≥90%\nof the initial efficiency for 1000 h under 1 sun and 65 °C operation.