Novel approach toward hole-transporting layer doped by hydrophobic Lewis acid through infiltrated diffusion doping for perovskite solar cells

In this work, an alternative processing route for doping of hole-transporting layer (HTL) with improved hole extraction and passivation of anionic Pb-I antisite defects at the perovskite/HTL heterojunction is reported for the first time in perovskite solar cells (PSCs), referred as the infiltrated diffusion doping (INDD) method. In INDD processing, HTL is prepared by depositing the hole-transporting material and dopant sequentially in separate steps, involving deposition of the hole-transporting material (PTAA) in the first step, followed by the deposition of novel fluorine-containing hydrophobic Lewis acid dopant (LAD) in the second step, employing an orthogonal solvent with respect to the PTAA. To the best of our knowledge, it is a pioneer approach which replaces traditional blend casting doping technique for HTL. Consequently, the optimized PSC based on LAD doped PTAA by INDD processing shows a champion power conversion efficiency (PCE) of 20.32%, marking a record PCE in PSCs with a single dopant for PTAA reported to date, and superior long-term stability, retaining 93% of their initial efficiency in ambient environment without any encapsulation up to 1500 h.