Three-Layer-Stacked Graphene-Based Flexible Transparent Heater on a High-Heat Resistance Transparent Polyimide Substrate

The resistive heating of flexible transparent conductive films can be utilized to develop flexible transparent heaters for various applications. However, achieving high temperatures for transparent heaters is difficult owing to the lack of high-thermal resistance in conventional flexible substrates such as polyethylene terephthalate and polyethylene naphthalate. In this study, a flexible transparent heater was fabricated using three-layer-stacked graphene (3LG) on a high-heat resistance transparent polyimide (TPI) substrate. The 3LG transferred onto the TPI substrate was characterized by Raman, optical transmittance, Hall-effect, and atomic force microscopy measurements. The heater performance, including the surface temperature distributions, current-applied voltage and the surface temperature-applied voltage characteristics, long-term stability, and heating rates, was evaluated. The results showed that the 3LG/TPI heater achieved a high, visible-light transmittance and low-sheet resistance of 89.1% and 210 Ω/sq, respectively. Furthermore, the 3LG-based flexible transparent heater demonstrated a uniform surface temperature distribution, high T T of 196 °C at V = 20\;V, V = 20 V , which are unachievable with conventional flexible substrates, and a rapid heating rate with a time constant of less than 1 s. The superior performance was maintained even under bending conditions. These results suggest that this device has a tremendous potential for future applications that require flexibility at high temperatures, including those in the aerospace industry.