Flexible Metal/Oxide/Metal Transparent Electrodes Made of Thermally Evaporated MoO3/Ag/MoO3 for Thin Film Heaters

The authors report on thermally‐evaporated MoO3/Ag/MoO3 multilayer films as a flexible and transparent electrode for high performance flexible thin film heaters (TFHs). Using thermal evaporation, the authors obtain highly flexible MoO3/Ag/MoO3 multilayer films on colorless polyimide substrate without plasma damage. To optimize the thickness of the Ag interlayer, the authors investigate the electrical, optical, morphological, and mechanical properties of MoO3/Ag/MoO3 multilayers as a function of Ag interlayer thickness. Based on a figure of merit value, the authors obtain an optimal MoO3/Ag/MoO3 electrode with a low sheet resistance of 3.17 Ohm/square, a high optical transmittance of 77.85%, and critical bending radius of 1 mm, which are acceptable for fabrication of TFHs. The flexible TFHs (25 × 25 mm2) fabricated on a thermally evaporated MoO3/Ag/MoO3 electrode shows a high saturation temperature of 118 °C even at a low input power of 2.5 W (input voltage 2.5 V) due to very low sheet resistance. Successful operation of the flexible TFHs indicate that the thermally‐evaporated MoO3/Ag/MoO3 film is a promising alternative transparent electrode to substitute sputtered Sn‐doped In2O3 (ITO) films for highly transparent and flexible TFHs. A flexible and transparent thin film heater (TFH) is fabricated on a thermally‐evaporated MoO3/Ag/MoO3 multilayer electrode on a 50‐µm‐thick CPI substrate. The TFH shows better performance than conventional ITO‐based thin film heaters due to the low resistance and outstanding flexibility of the MoO3/Ag/MoO3 multilayer.