Dopant-free hole-transporting materials based on a simple nonfused core with noncovalent conformational locking for efficient perovskite solar cells

Abstract

Developing dopant-free hole-transporting materials (HTMs) toward perovskite solar cells (PVSCs) is essential to their commercial deployment. In this work, two dopant-free organic HTMs (Q20 and Q21) based on a simple nonfused core with noncovalent conformational locking have been design and synthesized. It is found that, upon incorporation of the thiophene−3,4-ethylenedioxythiophene (EDOT)−thiophene, both Q20 and Q21 exhibit a high intrinsic hole mobility over 10 −4 cm 2 V −1 s −1 , thus leading to the desirable electronic properties in dopant-free PSCs. Owing to its high hole mobility, deep lying HOMO level, and excellent thin film quality, the dopant-free Q21-based PSCs exhibit an efficiency of 18.05% with negligible hysteresis. Notably, the devices based on dopant-free Q21 can retain more than 90% of their initial PCEs after being stored at ambient conditions for 1000 h. These results demonstrate that the good potential of the nonfused core with S–O conformational locking as building block for developing dopant-free small organic HTMs toward high-performance PSCs. • Two new dopant-free small organic HTMs have been designed and synthesized. • The thiophene−3,4-ethylenedioxythiophene−thiophene group was used as the π-bridge. • S–O conformational locking endows the HTM with high mobility over 10 −4 cm 2 V −1 s −1 . • An efficiency of 18.05% was achieved by dopant-free PSC based on Q21.