Efficient and Stable Perovskite Solar Cells with a High Open‐Circuit Voltage Over 1.2 V Achieved by a Dual‐Side Passivation Layer

Abstract Suppressing nonradiative recombination at the interface between the organometal halide perovskite (PVK) and the charge‐transport layer (CTL) is crucial for improving the efficiency and stability of PVK‐based solar cells (PSCs). Here, a new bathocuproine (BCP)‐based nonconjugated polyelectrolyte (poly‐BCP) is synthesized and this is introduced as a “dual‐side passivation layer” between the tin oxide (SnO 2 ) CTL and the PVK absorber. Poly‐BCP significantly suppresses both bulk and interfacial nonradiative recombination by passivating oxygen‐vacancy defects from the SnO 2 side and simultaneously scavenges ionic defects from the other (PVK) side. Therefore, PSCs with poly‐BCP exhibits a high power conversion efficiency (PCE) of 24.4% and a high open‐circuit voltage of 1.21 V with a reduced voltage loss (PVK bandgap of 1.56 eV). The non‐encapsulated PSCs also show excellent long‐term stability by retaining 93% of the initial PCE after 700 h under continuous 1‐sun irradiation in nitrogen atmosphere conditions.