Quantum Molecular Dynamical Calculations of PEDOT 12-Oligomer and its Selenium and Tellurium Derivatives

Abstract

We present simulation results, computed with the Car-Parrinello molecular dynamics method, at zero and ambient temperature (300 K) for poly (3,4-ethylenedioxythiophene) [PEDOT] and its selenium and tellurium derivatives PEDOS and PEDOTe, represented as 12-oligomer chains. In particular, we focus on structural parameters such as the dihedral rotation angle distribution, as well as how the charge distribution is affected by temperature. We find that for PEDOT, the dihedral angle distribution shows two distinct local maxima whereas for PEDOS and PEDOTe, the distributions only have one clear maximum. The twisting stiffness at ambient temperature appears to be larger the lighter the heteroatom (S, Se, Te) is, in contrast to the case at 0 K. As regards point charge distributions, they suggest that aromaticity increases with temperature, and also that aromaticity becomes more pronounced the lighter the heteroatom is, both at 0 K and ambient temperature. Our results agree well with previous results, where available. The bond lengths are consistent with substantial aromatic character both at 0 K and at ambient temperature. Our calculations also reproduce the expected trend of diminishing gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital with increasing atomic number of the heteroatom.

Vibrational spectra of neutral and doped oligothiophenes and polythiophene

“…There have been many calculations of the effect of doping on the structure of the oligothiophenes, PT and related materials e.g. [62][63][64][65][66] There is general agreement that doping induces the quinoid-type structure from the aromatic structure of the neutral systems (see Fig. 11 for an illustration of the structures) and our results are consistent with this picture.…”

“…Isolated molecule DFT calculations show that the molecular structures are not greatly modied on doping and since the INS spectrum largely depends on the structure, this does not change much. In contrast, as shown by others, [62][63][64][65][66] the electronic structure is greatly modied and this accounts for the major changes in the infrared and Raman spectra.…”

Mixed Ionic-Electronic Transport in Polymers

“…Thus, conjugated chains are not able to conform themselves to particular ions due to the limited local segmental motion to assist ion motion. Fluctuations in the dihedral angle between repeat units [e.g., the ethylenedioxy rings on poly(3,4-ethylenedioxythiophene) (PEDOT)] may impart some small ability for coordinating sites to reorient in response to adjacent cations, particularly in amorphous domains (38,39). As with ion solvation, in phase-separated systems (types I-IV), segmental motion in the nonconjugated polyelectrolyte/polymer electrolyte-rich domains promotes ionic transport.…”

DFT study of new organic materials based on PEDOT and 4-[2-(2-N, N-dihydroxy amino thiophene) vinyl] benzanamine

“…Where k is the Boltzmann constant [55][56]. Other calculated values published of the HOMO-LUMO gap in the PEDOT using different DFT method, range from 0.7 eV to 2.7 eV [7,43,57,[58][59][60][61]. The experimental conductivity of PEDOT is as high as 550 S/cm [62].…”