Designing a Flexible and Transparent Ultrarapid Electrothermogenic Film Based on Thermal Loss Suppression Effect: A Self-Fused Cu/Ni Composite Junctionless Nanonetwork for Effective Deicing Heater

Transparent heaters (THs) are one-size-fits-all materials used in electronics such as smart windows, wearable applications, and deicing devices. Copper-based THs, which are the most promising materials, still face some problems such as increasing electrical resistance at the intersections of each nanowire and easy degradation owing to oxidation. To overcome these problems, the formation of a junctionless network whose nanowire intersections are fused by using a composite of copper and the oxidation-resistant material is considered as one of the best strategies. Herein, we report a junctionless copper/nickel-nanonetwork-based TH formed on a polymer nanofiber by combining electrospinning and electroless deposition. This two-step wet process enables the formation of a junctionless network composed of a copper/nickel alloy. The THs showed outstanding heating characteristics (the power efficiency reached 421.7 °C cm²/W) which are suitable for the deicing application. Furthermore, we revealed that prominent heating characteristics are realized because of decreasing thermal loss at intersections during application of current, which we term "thermal loss suppression effect". Simulating thermal losses at intersection models of a junctionless network and a junction network based on the finite element method, we estimated the thermal loss originated from the network geometry. This insight may contribute to the design of high-performance electrothermal materials.