To capitalize on these tunable properties, the ASPIRE device employs a carefully engineered layered structure optimized for mid-IR applications. The ASPIRE device is fabricated in a layered asymmetric electrochemical cell structure, with PEDOT:PSS as the active material at the top working electrode and the charge storage layer at the bottom counter electrode (Fig. ). This design differs from the visible-light electrochromic device, where the active electrochromic layer is underneath the transparent electrode. In mid-IR, the active material (i.e., PEDOT:PSS) needs to be the outermost layer to maximize the transmission of thermal radiation from PEDOT:PSS to the environment. If the current collector is located at the outmost layer, the constant adsorption by the current collector layers reduces the IR tunability of the device.