Stable and Efficient Indoor Photovoltaics Through Novel Dual‐Phase 2D Perovskite Heterostructures

2D perovskite materials are ideal candidates for indoor photovoltaic (IPV) applications due to their tunable bandgap, high absorption coefficients, and enhanced stability. However, attaining uniform crystallization and overcoming low carrier mobility remain key challenges for 2D perovskites, limiting their overall performance. In this study, a 2D perovskite light-absorbing layer is constructed using a Dion-Jacobson (DJ)-phase EDA(FA)4Pb5I16 (n = 5) and introduced butylammonium iodide (BAI) for interface modification, thereby creating a novel DJ/Ruddlesden-Popper (RP) dual 2D perovskite heterostructure. By adjusting the thickness of the BAI-based perovskite layer, the relationship between interfacial defect states and carrier mobility is investigated under varying indoor light intensities. The results indicate that, by achieving a balance between interfacial defect passivation and carrier transport, the optimized 2D perovskite device reaches a power conversion efficiency (PCE) of 30.30% and an open-circuit voltage (VOC) of 936 mV under 1000 lux (3000 K LED). 2D-DJ/RP perovskite IPV exhibits a twentyfold increase in T90 lifetime compared to 3D perovskite devices. It is the first time to systematically study 2D perovskites in IPV applications, demonstrating that rationally designed and optimized 2D perovskites hold significant potential for fabricating high-performance indoor PSCs.