Interfacial modification using the cross-linkable tannic acid for highly-efficient perovskite solar cells with excellent stability

Although the performance of perovskite solar cells (PSCs) has been dramatically increased in recent years, stability is still the main obstacle preventing the PSCs from being commercial. PSC device instability can be caused by a variety of reasons, including ions diffusion, surface and grain boundary defects, etc. In this work, the cross-linkable tannic acid (TA) is introduced to modify perovskite film through post-treatment method. The numerous organic functional groups (–OH and CO) in TA can interact with the uncoordinated Pb2+ and I− ions in perovskite, thus passivating defects and inhibiting ions diffusion. In addition, the formed TA network can absorb a small amount of the residual moisture inside the device to protect the perovskite layer. Furthermore, TA modification regulates the energy level of perovskite, and reduces interfacial charge recombination. Ultimately, following TA treatment, the device efficiency is increased significantly from 21.31% to 23.11%, with a decreased hysteresis effect. Notably, the treated device shows excellent air, thermal, and operational stability. In light of this, the readily available, inexpensive TA has the potential to operate as a multipurpose interfacial modifier to increase device efficiency while also enhancing device stability.