Theoretical Study of New Compounds (D1-BT-EDOT-BT-D2-A) Based on 3, 4-Ethylenedioxythiophene (EDOT) and Benzothiadiazole (BT) for Dye Sensitized Solar Cells

Abstract

In this study, we investigate a series of novel metal-free organic dyes for DSSCs. These molecules carry as a central donor unit 3,4 ethylenedioxythiophene (EDOT), and as a π-acceptor the same benzothiadiazole (BT), and a different donor unit constituted of Phenylene, Thiophene, Fluorene, Carbazole and Anthracene, and they were designed with the structure (D1-BT-EDOT BT-D2-A). In addition, the Density Functional Theory DFT/B3LYP/6-31G (d, p) method and Time Dependant Density Functional Theory (TD/DFT) calculations have been used to study the optimized structures and optoelectronic properties of these dyes, of which they have coplanar structures, and their energy levels LUMO and HOMO can have a positive effect on the process of electron injection and dye regeneration. The HOMO-LUMO gap energy and the wavelength of absorption spectrum (λmax) were compared to the experimental data, while a low band gap appeared in the molecule containing Thiophene repeating units. Moreover, several quantum chemical properties such as ionization potential (IP), electron affinity (EA), hardness (η), electrophilicity index (ω) and chemical potential (μ) were also calculated and discussed extensively in the document. Our calculations results demonstrate that these compounds can be used as potential sensitizers for TiO2 nanocrystalline solar cells.