Molecular Glass Interface Engineering Enables Highly Efficient and Stable Inverted Perovskite Solar Cells

Perovskite solar cells with inverted configuration (p–i–n) offer simple, low‐temperature fabrication and high open‐circuit voltage, but they are limited by poor thermal and moisture stability. Here, we introduce solution‐processable amorphous molecular glass electron‐acceptor interlayers, comprising two fused fluoranthene imide (FFI) derivatives and a diketopyrrolopyrrole (DPP) analog, which simultaneously enhance the efficiency and operational durability of MAPbI 3 p–i–n devices. These glassy films utilize strong π – π stacking, electron‐withdrawing triazine and thiophene units, and inherent hydrophobicity to optimize energy‐level alignment with PCBM, reduce ion migration, and prevent moisture ingress. The addition of FFI increases the champion power conversion efficiency (PCE) from 14.6% to 15.5% and raises the water contact angle from 77° to 108°. Under continuous maximum power point tracking at 85°C, FFI‐modified cells retain over 90% of their initial PCE after 96 h, while control devices degrade within 48 h. X‐ray diffraction and UV–Vis measurements confirm the sustained integrity of the α ‐phase and minimal formation of PbI 2 . This interfacial engineering approach offers a scalable pathway to high‐performance, durable perovskite photovoltaics.