Density functional theory [B3LYP/6‐311G(d,p)] study of a new copolymer based on carbazole and (3,4‐Ethylenedioxythiophene) in their aromatic and polaronic states

Abstract

ABSTRACT:We report a theoretical study of a new copolymer based on (Carbazole and Ethylenedioxythiophene) n (n ¼ 1-3) in their neutral and oxidized states, by using B3LYP/6-311G(d,p) calculations and thus deduce its optoelectronic properties. We discuss the influence of chain length of these properties. We also discuss the experimental UV-Visible spectrum for (PolyvinylcarbazolePoly(3,4-ethylenedioxythiophene)) (PVK-PEDOT) copolymer powder for comparison. Conformational analysis shows that there are no big changes in the structural parameters of the oligomers in their neutral form. After oxidation the oligomers become more planar and show a quinoidal character. The electronic states of monomers (Cbz-Edot) based Carbazole (Cbz) and Ethylenedioxythiophene (Edot), were elucidated by molecular orbital calculations using B3LYP/6-311G(d,p). The HOMO, LUMO, and gap energies E g were also deduced for the stable structure of the neutral, polaronic, and bipolaronic forms. Electronic transition energies and oscillator strengths of copolymers were obtained by the ZINDO, TD-DFT, and CIS methods. Band gaps of the corresponding polymers were obtained by extrapolating oligomer gaps to infinite chain lengths. These results will be compared with the experimental values obtained by optical spectrum. The optoelectronic properties of the (Cbz-Edot) 3 led us to suggest that this oligomer is a good model to reflect those of the parent polymer.

Modeling of photoactive conjugated donor–acceptor copolymers: the effect of the exact HF exchange in DFT functionals on geometries and gap energies of oligomer and periodic models

“…One reason for this can be that the polymers P1-P3 have long CRUs, which leads to fewer data points for the extrapolation and all the points are located at low 1/n values (r0. 16) where the changes in the HOMO-LUMO gap are small. Another reason can be that the polymers P1-P3 are copolymers in which the building components of one CRU have HOMOs (and LUMOs) at different energies.…”

“…Usually, the polymers are studied by modeling isolated oligomers of increasing length using density functional theory (DFT) and fitting the calculated structural or electronic properties either as a function of the inverse of n (1/n), where n is the number of the constitutional repeating units (CRUs), or as a function of the inverse of the number of the double bonds (N) along the shortest path of the polymer backbone, thus yielding an extrapolation for the polymer properties. [12][13][14][15][16][17][18][19] The energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), i.e. hereafter called the HOMO-LUMO gap, is one of the properties of interest and can be evaluated directly from the Kohn-Sham eigenvalues.…”

Enzyme Immobilization on Polymer Membranes: A Quantum and Molecular Mechanics Study

“…The electrostatic charges on large fragments of external amino acids were calculated in the frame of density functional theory (DFT) using the Löwdin method as implemented in NWChem [15]. All quantum calculations were performed by using the B3LYP [16] hybrid functional and double-ζ basis set (6-31G*) for each atom of the enzyme and polysulfone surfaces. The thresholds for the energy convergence in the self-consistent field procedure and the root-mean-square of the electron density were set to 10 −6 (au) and to 2 × 10 −5 (au), respectively.…”

Electric and Photoelectric Properties of 3,4–Ethylenedioxythiophene‐Functionalized n‐Si/PEDOT:PSS Junctions

“…The HOMO and LUMO energy levels of the thiophene (thienyl) and EDOT units are also shown in Figure 6a,w ith the values adapted from previous computational and experimental work. [47][48][49][50] As shown, the energy barrier between the VB and HOMO of the EDOT and thiophene units is low ( % 1.5 eV), which suggestst hat hole transport through these monolayers will have al argee nhancement relative to that fora na lkyl monolayer. [46] However,a st he LUMO exhibits al arge energy barrierf or electron transfer from the CB, no enhancement in electron transport should occur relative to hole transport.…”