Enhancing Efficiency and Stability of Planar Perovskite Solar Cells via PBDB ‐T/ IT ‐ 4F Interface Engineering

Comprehensive Summary Planar perovskite solar cells (PSCs) have attracted significant attention in recent years due to their promising applications in renewable energy. However, their practical application is hindered by interface defects, energy level mismatch with the hole transport layer (HTL), and degradation induced by moisture and oxygen. To address these challenges, this study investigates the incorporation of the organic polymer PBDB‐T to modify the perovskite/HTL interface. Our findings demonstrate that PBDB‐T effectively induces p ‐type doping at the perovskite surface, leading to an increased work function and improved defect passivation. Furthermore, the synergistic combination of PBDB‐T with IT‐4F, based on our prior research, creates an internal encapsulation that effectively mitigates moisture and oxygen ingress. As a result, the optimized PSCs achieved a high open‐circuit voltage ( V OC ) of 1.18 V and a power conversion efficiency (PCE) of 25.14%. Notably, these devices exhibited excellent long‐term stability, retaining 84% of their initial efficiency after 4200 h of storage under a nitrogen atmosphere.