Improved Performance of Perovskite Solar Cells by Fine-Tuning Dibenzofuran-Based Hole Transporting Materials

In perovskite solar cells (PSCs), the properties of hole transporting materials (HTMs) have a significant effect on device performance. Molecular engineering of HTMs has been proved to be an effective way to fine-tune material properties and device performance. In this work, a series of spiro-type HTMs with dibenzofuran units as edge groups were developed by varying the substitution positions. It is noted that a newly-developed molecule (named spiro-4) exhibits more matched energy levels with perovskite, a higher glass transition temperature, higher hole mobility, better film-forming ability, and enhanced hole extraction ability than other positional isomers. When used in devices, spiro-4 delivers an impressive power conversion efficiency of 23.38%, which is obviously higher than other dibenzofuran-based counterparts or commercial spiro-OMeTAD. Most importantly, a spiro-4-based device also showed superior stability. The findings provide a promising way to obtain efficient and stable PSCs. Spiro-4 exhibits more matched energy levels with perovskite, a higher glass transition temperature, higher hole mobility, and enhanced hole extraction ability than other positional isomers, delivering a power conversion efficiency of 23.38%.