Figure 1

Schematic picture of the electrochemically gated transistor or EGT. The sample (PPV) is placed in an electrolyte solution. The electrochemical potential of the sample is controlled with respect to a reference electrode using a potentiostat. The conductivity was measured by applying a small dc bias between source and drain. The enlargement shows schematically how the holes on the polymer chain are compensated by the anions in the film.Reuse & Permissions

Figure 2

Electrochemical injection of holes into the PPV film. (a) The differential charge $\Delta Q(\widetilde{{\mu }_e})$ stored in PPV when successive 10 mV steps are applied. The potential is defined with respect to the Ag pseudoreference. The arrows show the two scanning directions: doping and dedoping while changing $\widetilde{{\mu }_e}$. (b) Doping per monomer $c(\widetilde{{\mu }_{\mathrm{e}}})$ calculated from the data in (a). The reversible doping range extends over 4 orders of magnitude.Reuse & Permissions

Figure 3

The $E$ dependence of the experimentally determined DOS ($g(E)$) where $E$ is with respect to the vacuum level. The horizontal dashed line marks the HOMO position found from cyclic voltammetry [28, 29]. (a) $E$ vs $g(E)$ using $\mathrm{P}{\mathrm{F}}_6^{-}$ and $\mathrm{C}\mathrm{l}{\mathrm{O}}_4^{-}$ as anions. A Gaussian function with $\sigma =0.19\mathrm{e}\mathrm{V}$ (area A) fits the data well. (b) $E$ vs $g(E)$ for $\mathrm{P}{\mathrm{F}}_6^{-}$ on a linear-log scale. Below $g=0.1\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}\mathrm{e}\mathrm{s}/(\mathrm{e}\mathrm{V}\mathrm{m}\mathrm{o}\mathrm{n}\mathrm{o}\mathrm{m}\mathrm{e}\mathrm{r})$ deviations from the Gaussian fit are visible. The filled squares are the PPV FET-data by Tanase et al. [18], which are well described by an exponential function. At the lowest values of $g(E)$ additional structure appears, which in a limited energy range would allow a description with a Gaussian with a width of 0.11 eV (area B) as used for PPV LEDs by Martens et al. [9] and Tanase et al. [18].Reuse & Permissions

Figure 4

(a) The hole mobility ($\mu$) calculated from the conductivity ($\sigma$- the inset) as function of doping. Because the measurements had to be performed in a two-point contact configuration, the flattening of $\sigma$ at high $c$ might be caused by contact resistances. Hence, actual values of $\sigma$ or $\mu$ might be even higher. (b) The dependence of hole mobility on energy or electrochemical potential $\widetilde{{\mu }_e}$. At lower doping, corresponding to energies $E>-5.2\mathrm{e}\mathrm{V}$, we have included $\mu$ (closed symbols) determined in a solid-state FET and LED by Tanase et al. [18]. The deviations are discussed in the text. Both plots are on a logarithmic-linear scale.Reuse & Permissions