Two hole-transporting materials (HTMs) based on carbohelicene cores, CH1 and CH2, are developed and used in fabricating efficient and stable perovskite solar cells (PSCs). Owing to the rigid conformation of the helicene core, both compounds possess unique CH-π interactions in the crystalline packing pattern and good phase stability, which are distinct from the π-π intermolecular interactions of conventional planar and spiro-type molecules. PSCs based on CH1 and CH2 as HTMs deliver excellent device efficiencies of 19.36 and 18.71%, respectively, outperforming the control device fabricated with spiro-OMeTAD (18.45%). Furthermore, both PSCs exhibit better ambient stability, with 90% of initial performance retained after aging with a 50-60% relative humidity at 25 °C for 500 h. Due to the low production cost of both compounds, these newly designed carbohelicene-type HTMs have the potential for the future commercialization of PSCs.
Keywords: helicenes; hole-transporting materials; intermolecular interactions; long-term stability; perovskite solar cells.