A highly conductive and flexible metal mesh/ultrathin ITO hybrid transparent electrode fabricated using low-temperature crystallization

The low-temperature processing of transparent electrodes on polymer substrates is an increasingly important issue in lightweight and flexible optoelectronic devices and low-temperature processing is essential since most polymer substrates cannot withstand high temperatures. We analyzed the electrical and optical characteristics of indium tin oxide (ITO) films according to the various crystallization conditions and confirmed that the low-temperature crystallized ITO has a rhombohedral structure. The ultrathin ITO films were crystallized at a temperature of 250 °C, which is lower than the glass transition temperature of polyimide substrates, and a hybrid transparent electrode with a metal mesh was formed. Our hybrid transparent electrode had a high transmittance of 77.4% and a low sheet resistance of 6.3 Ω/sq. After 1000 bending cycles at a bending radius of 6 mm, the hybrid transparent electrode maintained a sheet resistance of 6.5 Ω/sq. We applied rhombohedral ITO to the device rather than the commonly used cubic ITO, and as a result, it showed excellent electrical properties and better bending-stress stability.