Double-Helicene-Based Hole-Transporter for Perovskite Solar Cells with 22% Efficiency and Operation Durability

Amelioration of the mobility and, in particular, the thermal stability of a hole-transporting molecular semiconductor is a practicable strategy to attain the enhancement of both power conversion efficiency (PCE) and operational durability of perovskite solar cells (PSCs). Here a cost-effective double-[4]­helicene-based molecular semiconductor (DBC-OMeDPA) is synthesized for a solution-deposited thin film, exhibiting an improved hole mobility in comparison with state-of-the-art spiro-OMeTAD control. X-ray crystallographic analysis and theoretical calculation reveal the three-dimensional molecular stacking and multidirectional hole-transporting property of DBC-OMeDPA, clarifying the microscopic mechanism of the hole-transport process. A better PCE of 22% at the AM 1.5G conditions is achieved for PSCs with DBC-OMeDPA as the hole-transporter. Moreover, PSCs using DBC-OMeDPA characteristic of an elevated intrinsic glass transition temperature of 154 °C maintain a stable PCE output for hundreds of hours at 60 °C under equivalent full sunglight soaking.