Peripherally Fluorinated Tetraphenylethene: New Electron Extraction Interlayers for n‐i‐p Perovskite Solar Cells

ABSTRACT Tetraphenylethene (TPE) is a classic structural motif frequently incorporated into materials for optoelectronic devices due to its structural versatility. However, when used in perovskite solar cells, these TPE‐based layers exhibit suboptimal interfacial compatibility, leading to inefficient charge carrier extraction and reduced device stability. To address these issues, we have introduced hydrophobic fluorinated phenyl groups onto the TPE structure, electron transport interfacial materials, such as 1,1,2,2‐tetrakis(2',3',4',5',6'‐pentafluoro‐[1,1'‐biphenyl]‐4‐yl)ethene ( TFP‐TPE, 1 ) and 1,1,2,2‐tetrakis(3',5'‐bis(trifluoromethyl)‐[1,1'‐biphenyl]‐4‐yl)ethene ( TFMP‐TPE, 2 ). X‐ray diffraction study shows that both TPE molecules 1 and 2 were significantly twisted. These fluorinated materials effectively inhibit molecular aggregation, enhance surface wettability, and form strong bonds with perovskite precursors. As a result, it leads to a slower perovskite crystallization rate, improved interfacial quality, and enhanced charge carrier collection. Steady‐state and time‐resolved photoluminescence measurements reveal enhanced electron extraction and transport properties in PSCs incorporating perfluorophenyl‐substituted TPE 1 as an interlayer. PSCs incorporating 1 set a new benchmark with an efficiency of 25.29%. To the best of our knowledge, this represents one of the highest efficiencies achieved with an interfacial material in PSCs. Moreover, unencapsulated devices incorporating 1 exhibit exceptional stability under humid conditions and elevated temperatures. This work highlights a highly effective and economically viable strategy for advancing organic interfacial materials in PSC applications, where the stronger hydrophobic character of TFP‐TPE over TFMP‐TPE plays a critical role in enhancing both efficiency and stability.