Polarons, Bipolarons, And Absorption Spectroscopy of PEDOT

Abstract

Electronic structure and optical absorption spectra of poly­(3,4-ethylenedioxythiophene) (PEDOT) for different oxidation levels were studied using density functional theory (DFT) and time-dependent DFT. It is shown, that the DFT-based predictions for the polaronic and bipolaronic states and the nature of corresponding optical transitions are qualitatively different from the widely used traditional picture based on semi-empirical pre-DFT approaches that still dominate the current literature. On the basis of the results of our calculations, the experimental Vis/NIR absorbance spectroscopy and the electron paramagnetic resonance spectroscopy are re-examined, and a new interpretation of the measured spectra and the spin signal, which is qualitatively different from the traditional interpretation, is provided. The findings and conclusions concerning the nature of polaronic and bipolaronic states, band structure and absorption spectra presented for PEDOT, are generic for a wide class of conducting polymers (such as polythiophenes and their derivatives) that have a similar structure of monomer units.

The intrinsic volumetric capacitance of conducting polymers: pseudo-capacitors or double-layer supercapacitors?

“…For the case without counterions, DE g is not sensitive to the oxidation level. 32 However, for the case of the counterions the gap between LUMO and HOMO levels gradually decreases as the ion concentration is increased, which is related to the effect of the disorder potential caused by counterions. 69,70 This is illustrated in Fig.…”

“…(A detailed analysis of the polaronic and bipolaronic states in PEDOT was recently given in ref. 32). The charging of the polymer chains is accompanied by the addition of the negative counterions to the system to maintain the electroneutrality as prescribed by eqn (2).…”

“…60 This functional accounts to 100% Hartree-Fock (HF) at the long range, and 22% of the HF at the short range, and it is particularly suited for description of localized polarons/bipolarons in polymeric conjugated systems. 32,61 For the basis set we chose 6-31G(d) since it represents a balance between accuracy and required computational efforts. We also performed test runs with 6-31G(d)+ basis set to ensure that the absence of diffusive functions does not affect the obtained results, see Fig.…”

Impact of Morphology on Charge Carrier Transport and Thermoelectric Properties of N‐Type FBDOPV‐Based Polymers

“…[ 18,49 ] Upon doping, energy levels lying inside the electronic band gap of the ground state allow new optical transitions that can be used as a fingerprint to identify the formation of charge‐transfer complexes (CTCs) by UV–vis–NIR spectroscopy. [ 52 ] The absorption spectra of neat and doped films of P(FBDOPV‐F ) and P(FBDOPV‐2T‐C 12 ) are presented in Figure a,b.…”

On the anomalous optical conductivity dispersion of electrically conducting polymers: ultra-wide spectral range ellipsometry combined with a Drude–Lorentz model

“…4,12 The polarons are relatively well understood in terms of energy levels, spin and DC transport. 13 However, there are controversies regarding suitable models to describe the materials' AC behavior and extension to optical conductivity, which is tightly connected to transport properties in combination with vibrational resonances. 3,[14][15][16][17] The complex-valued optical conductivity (s) is interconnected with the permittivity or dielectric function (e) of the material via: 18,19 s(o) = ie 0 o[e N À e(o)], (1) where e N is the permittivity offset at high frequencies (beyond the measurement limits), i is the imaginary unit, e 0 is the vacuum permittivity, and o is the angular frequency.…”