Dual-Band Electrochromism: Plasmonic and Polaronic Mechanisms

Electrochromic windows that dynamically absorb incident solar irradiation are envisioned as smart technology devices that can reduce power consumption in buildings and accelerate progress toward sustainable development. While regulating the visible light in interior spaces to suite the comfort of occupants, electrochromic windows also offer thermal control by controlling the flux of solar energy, including infrared radiation. The ability to selectively modulate visible and the infrared solar transmittance is denoted as dual-band electrochromism. Dual-band control can be achieved by employing materials that absorb light in different spectral regions when electrochemically charged, with light absorption due to either a polaronic or a plasmonic mechanism, depending on the charging conditions. In this perspective, we discuss how adopting a plasmonic or a polaronic approach can affect the performance of an electrochromic device in terms of different quantitative figures-of-merit, and the challenges and opportunities for designing better dual-band electrochromic devices in the future.