Probing the effect of acceptor engineering in benzothiadiazole-based D-A-D-typed hole-transporting materials for perovskite solar cells

Hole-transporting materials (HTMs) is very important for improving the stability and efficiency of perovskite solar cells (PSCs) because it plays a crucial role for the exciton dissociation at the interface and the following hole transport. To improve the performance of HTMs, the strategy of extension and rigidification of the π-conjugated acceptor in donor-acceptor-donor-typed HTMs is evaluated in this work. Theoretical calculations indicate that all the predicted HTMs display the suitable energy levels to ensure the effortless hole transfer at the perovskite/HTM interface. More importantly, our results reveal that extending the acceptor group is a good strategy to promote the hole transport in HTMs. Meanwhile, the bent molecular conformation by rigidifying the conjugated acceptor can also improve the hole mobility of HTMs due to the better molecular planarity and enhanced intermolecular stacking and orbital overlapping. All the predicted HTMs display the higher hole mobility than that of the YN1. The higher mobility and matched energy levels of predicted HTMs are favorable for improving the performance of PSCs. In addition, the better optical property and solution property can also be anticipated for the new tailored HTMs. In summary, this work provides a useful strategy for the design of high-efficient HTMs, and three new designed HTMs are proposed as the potential candidates toward more efficient dopant-free HTMs.