Ultra-Wideband Transparent Conductive Electrode for Electrochromic Synergistic Solar and Radiative Heat Management

Electrochromic devices are a key technology to modulate optical and thermal energy for zero-energy buildings. With the sun as the heat source and deep space as the cold source, it would be beneficial to accomplish wideband regulation and control both solar and radiative heat simultaneously to obtain large heating and cooling performance. Here, a flexible ultra-wideband transparent conducting electrode (UWB-TCE) with low sheet resistance (Rs = 22.4 ohm/sq) and high optical transmittance (TUV–vis = 85.63%, Tnear-IR = 87.85%, and Tmid-IR = 84.87%) has been demonstrated to realize an electrochromic device that is capable of synergistic solar and radiative heat management. Enabled by the UWB-TCE, the metal-based electrochromic device can vary its emissivity between 0.12 and 0.94. The device can also switch between solar heating mode (high solar absorptivity and low thermal emissivity) and radiative cooling mode (low solar absorptivity and high thermal emissivity) by controlling the optimal electrodeposition morphology for surface plasmon resonance. The optimal solar absorptivity (α) and thermal emissivity (ε) of solar heating and radiative cooling mode are (α, ε) = (0.60, 0.20) and (0.33, 0.94), respectively. The UWB-TCE and dual-band solar and mid-IR electrochromic device can bring vast opportunities for applications in heat management, camouflage, display, and building energy efficiency.