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

With the rapid development 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 lithium bis(trifluoromethylsulfonyl)‐imide (Li‐TFSI)/4‐tert‐butylpyridine (t‐BP)‐doped hole‐transporting materials (HTM) have led to state‐of‐the art efficiency in 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 poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] (PTAA). The resulting Zn‐FP‐based PSCs achieve a maximum PCE of 20.34 % with hysteresis‐free current density‐voltage (J‐V) scans. Specifically, the unencapsulated device exhibits a significantly advanced 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 h under continuous 1‐sun equivalent illumination in N2 atmosphere in both forward and reverse J‐V scan. [ABSTRACT FROM AUTHOR]