Boron-nitrogen substituted planar cores: designing dopant-free hole-transporting materials for efficient perovskite solar cells.

Developing dopant-free hole-transporting materials (HTMs) is very important for improving the stability and increasing the power conversion efficiency of perovskite solar cells (PSCs). Herein, nine boron-nitrogen substituted tetrathienonaphthalene (BN-TTN) derivatives as hole-transporting materials (HTMs) were investigated using theoretical calculations combined with the Marcus theory and the Einstein relation. The results showed that the introduction of a boron-nitrogen group in tetrathienonaphthalene leads to a deep HOMO level, good thermal stability, and enhanced hydrophobicity. Importantly, most BN-TTN molecules possess larger hole mobility due to a broader distribution of the frontier molecular orbitals of the dimer. The BN-TTN core that matches with the size of the perovskite interface also increases the interfacial interaction and hole transfer from the perovskite layer to the HTM layer. The present findings can highlight the potential of BN-TTN core-based HTMs for efficient PSCs.