Trace Doping: Fluorine‐Containing Hydrophobic Lewis Acid Enables Stable Perovskite Solar Cells

With the rapid developments in perovskite solar cell (PSC), high efficiency has been achieved, but the long‐term operational stability is still the most important challenges for the commercialization of this emerging photovoltaic technology. So far, bi‐dopants Li‐TFSI/t‐BP doped hole‐transporting materials (HTM) have led to state‐of‐the art efficiency in n‐i‐p PSCs. However, such dopants have several drawbacks in terms of stability, including the complex oxidation process, undesirable ion migration and ultra‐hygroscopic nature. Herein, a fluorine‐containing organic Lewis acid dopant bis(pentafluorophenyl)zinc (Zn‐FP) with hydrophobic property and high migration barrier has been employed as a potential alternative to widely employed bi‐dopants Li‐TFSI/t‐BP for PTAA. The resulting Zn‐FP‐based PSCs achieve a maximum PCE of 20.34% with J‐V  hysteresis‐free. Specifically, the unencapsulated device exhibits significantly advancement of operational stability under the International Summit on Organic Photovoltaic Stability protocols (ISOS‐L‐1), maintaining over 90% of the original efficiency after operation for 1000 hours under continuous 1‐sun equivalent illumination in N2 atmosphere in both forward and reverse J‐V scan.