Highly flexible transparent electrodes using a silver nanowires-embedded colorless polyimide film via chemical modification

Abstract

Conducting metal oxides such as indium tin oxide (ITO) and Al-doped ZnO have been used for application in transparent conducting electrodes (TCEs), but they are not suitable for flexible transparent electrodes due to their brittleness. Silver nanowires (AgNWs) are one of the most promising alternatives to conducting metal oxides because of their high electrical conductivity and superior ductility, which are essential criteria for flexible optoelectronics. In order to develop high-temperature resistant flexible electrodes, we combined colorless polyimide (CPI) as a backbone matrix substrate with the AgNW network. In this work, we firstly demonstrate the hybrid transparent electrodes of AgNWs-embedded CPI encapsulated by a ZnO layer (ZnO/AgNWs-embedded CPI) via KOH treatment based chemical modification of the CPI film. The ZnO/AgNWs-embedded CPI substrate exhibited a low sheet resistance of 24 Ω sq⁻¹ while maintaining a high optical transparency of 81%. More importantly, the hybrid transparent electrodes exhibited superior thermal stability (heat treatment for 24 hours at 230 °C) with negligible conductivity decay and outstanding bending stability (stable for 10 000 bending cycles). ZnO/AgNWs-embedded CPI showed relatively low roughness (RMS, 9.6 nm) compared with non-embedded AgNWs on CPI (RMS, 82 nm). Embedding of AgNWs on top of the CPI film offers a good potential for application in flexible TCEs with thermal stability.