Strong Electron-Withdrawing Molecules Facilitating π-π Stacking and Charge Transfer Complexes at Buried Interface and...

To improve the interfacial match between the hole transport layer (HTL) and perovskite active layer (PAL) in inverted perovskite solar cells (PSCs), a strong electron-withdrawing molecule 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) is introduced to bridge the self-assembled monolayers (SAMs) [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) and PAL. F4TCNQ eliminates molecular voids in the SAMs via π-π stacking, forming charge-transfer complexes that homogenize interfacial potential and promote perovskite crystallization, increasing grain size from 0.53 to 0.88 µm. The cyano groups and fluorine atoms on F4TCNQ passivate Pb²⁺ and I^- defects through coordination and hydrogen bonding, suppressing ion migration and carrier nonradiative recombination. Meanwhile, p-type doping by F4TCNQ elevates the SAMs work function, reducing the hole extraction barrier by 0.12 eV and enhancing charge transfer driving force. Optimized devices achieve a champion power conversion efficiency of 25.91% with a high open-circuit voltage of 1.202 V, while retaining 91% efficiency after 1000 h of maximum power point tracking, attributed to stabilized ion dynamics and robust interfacial adhesion. This work demonstrates molecular bridging as a scalable strategy for high-performance photovoltaics.