Efficient dopant-free small-molecule hole transport material with D-A-D structure for inverted perovskite solar cells

Hole transport materials (HTMs) play an essential role in obtaining efficient and stable perovskite solar cells (PSCs). In particular, PSCs based on dopant-free small molecule hole transport materials (SM-HTMs) have the unique advantages of reproducibility and long-term stability. In this work, we design and synthesis a small molecule, FIMPA-C11, with a D-A-D structure, to serve as a HTM. The corresponding inverted planar PSCs achieve a satisfying efficiency of 17.60%, equivalent to 17.01% of the NiO counterpart, with superior stability and much lower processing temperature. The property and morphology of FIMPA-C11 film make it a better substrate for the crystallization of perovskite absorbing layer. The work enriches the category of HTMs and provides innovation for high-performance dopant-free SM-HTMs in PSCs.