Benzotriazole‐Functionalized Ionic Liquid and Superwettability‐Assisted Transfer Enable Air‐Stable, Large‐Area Copper Nanowires‐Based Flexible Transparent Electrodes

Copper nanowires (CuNWs) are promising for flexible transparent electrodes but suffer from lack of effective strategies to inhibit the oxidation-induced conductivity degradation, especially during large-area electrode preparation. Herein, a benzotriazole-functionalized ionic liquid ([BTAMMIM]TFSI) is introduced as an antioxidant layer to protect the CuNWs networks. Remarkably, the sheet resistance of the protected electrodes increases by only 0.54% compared to bare CuNWs after 60-day air exposure. Density functional theory (DFT) calculations and experiments reveal that the benzotriazole-functionalized cations and [TFSI] anions synergistically coordinate with copper, enabling exceptional oxidation resistance. By integrating with superwettability-assisted interfacial transfer strategy, large-area CuNWs@[BTAMMIM]TFSI composite electrodes (40 × 25 cm²) are fabricated with 37.2 Ω sq^-1 sheet resistance and 88.2% transmittance (550 nm). The electrodes maintain performance under acidic/alkaline conditions (pH 3/13) and high humidity (85% RH) at 85 °C. A demonstrated flexible smart window exhibits high transmittance modulation (6.1%-68.2%), fast response (< 0.2 s) and long-term stability, highlighting their potential in flexible optoelectronics.