Smart Targeting Layer on Silver Nanowire Electrodes Achieving Efficiency Breakthroughs in ITO-Free Conventional Flexible Organic Solar Cells

Abstract

Silver nanowire (AgNW) electrodes, known for their intrinsic flexibility and tunable optoelectronic properties, have garnered considerable attention for use in flexible organic solar cells (OSCs). However, in conventional OSCs, their low work function (WF) causes energy-level mismatches with classic aqueous hole transport layers (HTLs), while their poor hydrophilicity hinders the formation of optimized HTL morphology and crystallinity, posing challenges to their integration into high-performance OSCs. To address these issues, functionally targeted molecules with a thiol group at one end and strong electron-withdrawing, hydrophilic functional groups at the other are precisely engineered to wrap around the AgNW electrodes. The thiol group facilitates the formation of robust self-assembled molecules (SAMs) on the AgNW electrodes through stable S-Ag chemical bonds at room temperature. The strong electron-withdrawing groups generate notable molecular and interfacial dipoles that effectively raise the WF of AgNW electrodes. Notably, the hydrophilic groups not only improve electrode wettability but also promote strong hydrogen bonding interactions with HTL, leading to substantial improvements in the morphology and crystallinity of the HTL. This precision wrapping strategy enables the fabrication of high-efficient conventional flexible OSCs, achieving a record power conversion efficiency of 18.84 % (certified at 18.56 %) for flexible OSCs based on ITO-free transparent electrodes.