Interfacial Passivation Engineering for Highly Efficient Perovskite Solar Cells with a Fill Factor over 83%

Charge carrier nonradiative recombination (NRR) caused by interface defects and nonoptimal energy level alignment is the primary factor restricting the performance improvement of perovskite solar cells (PSCs). Interfacial modification is a vital strategy to restrain NRR and enable high-performance PSCs. We report here two interfacial materials, PhI-TPA and BTZI-TPA, consisting of phthalimide and a 2,1,3-benzothiadiazole-5,6-dicarboxylicimide core, respectively. The difunctionalized BTZI-TPA with imide and thiadiazole shows higher hole mobility, better aligned energy levels, and stronger interaction with uncoordinated Pb2+ on the perovskite surface, suppressing NRR and carrier accumulation at the interface of perovskite/spiro-OMeTAD and yielding enhanced open-circuit voltage and fill factor. Consequently, the PSC based on BTZI-TPA delivers a high efficiency of 24.06% with an excellent fill factor of 83.10%, superior to that (21.47%) of the reference cell without an interfacial layer, and 21.45% efficiency for the device with a scaled-up area (1.00 cm2). These results underscore the potential of imide and thiadiazole groups in developing interfacial layers with strong passivation capability, effective charge transport property, and fine-tuned energetics for stable and efficient PSCs.