The Role of Alpha‐Methylbenzyl Ammonium Iodide to Reduce Defect Densities in Perovskite Devices

Hybrid organic–inorganic perovskite photovoltaic has achieved unmatched power conversion efficiency (PCE) improvement in the last decade. Nevertheless, nonradiative recombination of charge carriers due to bulk and interface defects reduces the open‐circuit voltage (V _oc) and PCE of perovskite solar cells. Incorporating additives, process optimization, and interface engineering are among the effective approaches employed to reduce such issues. Herein, quasi‐2D p–i–n perovskite solar cells incorporating alpha‐methylbenzyl ammonium iodide (MBAI) cation with outstanding photovoltaic performance and stability are developed. MBAI incorporation results in films with excellent optical and electrical properties, leading to higher V _OC of ≈1.15 V, fill factor of above 77%, and stability of the device. A high open‐circuit voltage and fill factor and corrected power conversion efficiencies in the range of 15% are obtained for the prepared devices. The encapsulated solar cells show excellent operational stability under white light illumination in ambient air for >500 h. Due to the simple and robust preparation process, the investigated inverted perovskite solar cell can easily be combined with other solution‐processed thin film solar cells to form multijunction devices and can easily be integrated into different lightweight and flexible products.