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

## TL;DR

This paper introduces a new method to create stable, large-area copper nanowire electrodes using a protective ionic liquid and a transfer strategy, making them suitable for flexible electronics.

## Contribution

A novel antioxidant ionic liquid and superwettability-assisted transfer strategy are combined to enable air-stable, large-area copper nanowire electrodes.

## Key findings

- The protected electrodes show only a 0.54% increase in sheet resistance after 60 days of air exposure.
- Large-area composite electrodes (40 × 25 cm²) achieved 37.2 Ω sq⁻¹ resistance and 88.2% transmittance.
- The electrodes maintain performance under harsh conditions like high humidity and extreme pH.

## Abstract

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.

Benzotriazole‐functionalized ionic liquids, which exhibit excellent oxidation‐resistant properties for copper nanowires‐based flexible transparent electrode owing to the anion‐cation synergistic protective effect, are integrated with the superwettability‐assisted transfer, a strategy for the spontaneous transfer of copper nanowires from air–water interface to substrates driven by surface tension difference, to afford air‐stable, large‐area copper nanowires‐based flexible transparent electrodes.