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.