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 Pb 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 cm). 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.