Mohamed Hamidi

DFT Study of Polythiophene Energy Band Gap and SubstitutionEffects

Polythiophene (PTh) and its derivatives are polymer-based materials with a π-conjugation framework. PTh is a useful photoelectric material and can be used in organic semiconductor devices, such as PLED, OLED, and solar cells. Their properties are based on molecular structure; the derivatives contain different substitutes in the 3 and 5 positions, such as electron-donating or electron-withdrawing groups. All molecular geometries were optimized at B3LYP/6-31G(d,p) level of theory. The energy gap () between the HOMO and LUMO levels is related to the π-conjugation in the PTh polymer backbone. In this study, the DFT calculations were performed for the nonsubstituted and 3,5-substituted variants to investigate the stability geometries and electrical properties. The theoretical calculations show that the substituted forms are stable, have low , and are in good agreement with the experimental observations.

Structural and Electronic Properties of New Materials Based on Thiophene and Phenylene

Theoretical study on the geometries and electronic properties of new conjugated compounds based on thiophene and phenylene was carried out. The theoretical ground-state geometries and electronic structures of the studied molecules were obtained using the density functional theory (DFT) method at B3LYP level with 6-31G(d) basis set. The electronic properties were determined by ZINDO/s, CIS/3-21G(d), and TD//B3LYP/3-21G(d) calculations performed on the B3LYP/6-31(d) optimized geometries. The effects of the ring structure and the substituents on the geometries and electronic properties of these materials were discussed. The results of this study indicate how the electronic properties can be tuned by the backbone ring or side group and suggest these compounds as good candidates for opto-electronic applications.

Opto-electronic properties and molecular design of new materials based on pyrrole studied by DFT

In this work, we investigate oligopyrroles and derivatives, which serve as models for corresponding polymers. In order to discuss these materials, we carried out DFT calculations and used DFT methods to calculate ground state electronic structures. We are particularly interested in exploring the potential of several substituent groups as electron donors with numerous ties to electronic materials by exploring and comparing the energies of HOMO, LUMO, Gap energies, and structural properties. Results are discussed in comparison with the properties of the doped oligomers. The theoretical ground-state geometry and electronic structure of the studied molecules were obtained by the DFT method at B3LYP level with 6-31G(d) basis set. The opto-electronic properties of these materials were determined by ZINDO/s and TD//B3LYP/6-31G(d) calculations performed on the B3LYP/6-31(d) optimized geometries. The results of this study demonstrate how electronic properties can be tuned by the backbone ring or side group and suggest these compounds as good candidates for opto-electronic applications.

The bridged effect on the geometric, optoelectronic and charge transfer properties of the triphenylamine–bithiophene-based dyes: a DFT study

The dye-sensitized solar cells containing a triphenylamine unit as the electron donor connected with a terminal cyanoacrylic acid electron acceptor by 2,2′-bithiophene as π-bridged (D-π-A) has been investigated by density functional theory (DFT) at the B3LYP/6-31G(d) level to shed light on the bridged effect on geometric and electronic properties of the designed dyes. Also, time-dependent DFT (TD-DFT) at a TD-BH and H/6-31+G(d)//BH and H/6-31G(d) level of theory was selected to modulate the electronic absorption spectra and charge-transfer properties of studied dyes. The calculated results show that the strong electron-withdrawing groups bridged the 2,2′-bithiophene efficiently, reduce the energy gaps and provide a red shift of the absorption spectra. The calculated absorption spectra in tetrahydrofuran (THF) are in good agreement with available experimental value for dye D1. Generally, the fundamental parameters, such as vertical and adiabatic ionization potentials (IPa/IPv), vertical and adiabatic electron affinities (EAa/EAv), electron extraction potentials and hole extraction potentials, including hole/electron reorganization energies (λ+/λ−), of studied dyes have been discussed. The improved electronic coupling constant (

Density functional theory (B3LYP/6-31G*) study of oligothiophenes in their aromatic and polaronic states

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Bridging effect on structural and optoelectronic properties of oligothiophene

VRP), electron injection force (

DFT calculations of the local spin densities and oligomerization mechanism of thiophene-phenylene (TP) co-oligomers and derivatives

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