where is the charge carrier density, e is the elementary charge, is the permittivity of free 𝑛 𝑐 ε 0 space, and is the effective mass of the charge carrier. This tunability enables the reflectivity 𝑚 0 of conjugated polymers to be modulated electrochemically by tuning the carrier density (and thus the plasma frequency) in the polymer backbones. For example, in PEDOT:PSS, oxidation of the polymer delocalizes the π-bond electrons in the polymer backbone, generating polarons and bipolarons as p-type charge carriers (Fig. ), thereby increasing its IR reflectivity. Conversely, electrochemical reduction (dedoping) removes holes from the PEDOT backbones, decreasing the carrier density and enhancing its emissivity/absorptivity in the infrared regime. See Supplementary Note 1 for more details.