In Situ Graded Passivation via Porphyrin Derivative with Enhanced Photovoltage and Fill Factor in Perovskite Solar Cells

While perovskite solar cells (PSCs) have recently experienced a rapid rise in power conversion efficiency (PCE), the prevailing PSCs still contain nondesirable defects in the interior and interface of the perovskite layer, which limits further enhancement in PCE and device stability. Herein, a new D-pi-A-type zinc pyridine porphyrin derivative (ZnPP) is synthesized and used as a passivation molecular via the antisolvent process for modifying the typical perovskite bulk thin film, leading to a new type of PSC with a graded passivation ofthe perovskite layer. Impressively, it is found that ZnPP treatment significantly improves the quality of perovskite films and reduces charge transport losses through passivating the uncoordinated Pb2+ cations, yielding devices with a high efficiency of 21.08% with fill factor (FF) of 82.91% and demonstrating the promise of integration of perovskite bulk thin films with tailor molecular via graded modification.