Fig. 2: Thermodynamics of OMIECs.
a Temperature and ϕ dependence of the Gibbs free energy (with Hmix = 0, using \({\mu }^{{p}^{+}}=-60 \;{{{{{\rm{meV/mol}}}}}}\) and \({\mu }^{{p}^{0}}=0\)). Higher temperatures shift the minimum towards ϕ0 = 0.5 and to lower energies. b Measurement of the current flowing in a PEDOT:PSS thin-film at a different temperatures, in deionized water (DIW) and saltwater DIW:NaCl 100 mM (circles). Curves are fitted with a linear regression (solid lines). The experiment in DIW (see Methods for details) is used to estimate the contribution of the temperature-dependent mobility, which is then subtracted, leading to the blue dashed line. The same contribution is subtracted from the current measured in DIW:NaCl. The negative slope shows that, besides the increased mobility, the doping density is lowered. Note that at room temperature, the current drops by 8% with respect to when it is in distilled water (DIW), hence ϕ0(T = 300 K) = 0.08. c Calculated concentration of reduced PEDOT0 and doped/oxidized PEDOT+ in the film at different temperatures.
