Résumé
To understand the importance of the organic material of type donor-π-acceptor dyes (D-π-A), used for dye-sensitized solar cells (DSSCs), we present in this paper the result of six compounds based on thienopyrazine (D1-D6) studied by density functional theory (DFT) and time dependent DFT (TD-DFT) approaches to shed light on how the π-conjugation order influence the performance of the dyes. The electron acceptor (anchoring) group was 2-cyanoacrylic acid for all dyes whereas the electron-donor unit varied and the influence was investigated. The theoretical results have shown that TD-DFT calculations using the Coulomb attenuating method CAM-B3LYP with the polarized split-valence 6-31G (d, p) basis sets and the polarizable continuum model (PCM) were reasonably capable of predicting the excitation energies, the absorption and the emission spectra of the dyes. The study of structural, electronic and optical properties for these dyes could help to design more efficient functional photovoltaic organic materials. Key parameters in close connection with the short-circuit current density (Jsc), including light harvesting efficiency (LHE), injection driving force (ΔGinject) and total reorganization energy (ltotal), were discussed.