Multi-channel transport with inter-digitated electrode-enabled flexible transparent heater for optical and thermal regulations

Transparent heaters have various energy applications, especially in buildings, with the advantage of low energy consumption, leading to energy-efficient heating. They can be integrated into structures and color-tuned for enhanced aesthetics. Herein, we designed transparent flexible heaters with various structures based on the Joule heating effect through multi-channel transport with inter-digitated-electrode (IDE), suitable for low-power utility with high performance. The approach to increase heat generation is decreasing resistance and increasing current at the same applied voltage. Multi-channel silver (Ag) metal-oxide composite generates heat through the Joule effect with high visible light transmittance and infrared reflectance. By depositing Ag on a transparent conducting oxide, it is possible to form electrodes that serve as a medium for efficient heat transfer. We evaluated each transparent heater structure's electrical and optical characteristics to assess their suitability for window applications. Comparatively, the oxide/metal/oxide/metal/oxide-IDE heater shows visible transmittance (69 %) and excellent IR-cutting (90 %) by tuning the light propagation. This transparent IDE structure with a size of 2.5 × 2.5 cm² has sheet resistance (1.14 Ω/□) and rapid heating elevation (191 °C) at a bias of 3 V. This demonstrates that the functional design of electrodes can serve as energy-saving windows and selectively filter light propagation in useful ways.