title: DFT and TD-DFT calculation of new thienopyrazine-based small molecules for organic solar cells.
abstract: BACKGROUND
  Novel six organic donor-π-acceptor molecules (D-π-A) used for Bulk Heterojunction organic solar cells (BHJ), based on thienopyrazine were 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 solar cells. The electron acceptor group was 2-cyanoacrylic for all compounds, whereas the electron donor unit was varied and the influence was investigated.
  
  
  METHODS
  The TD-DFT method, combined with a hybrid exchange-correlation functional using the Coulomb-attenuating method (CAM-B3LYP) in conjunction with a polarizable continuum model of salvation (PCM) together with a 6-31G(d,p) basis set, was used to predict the excitation energies, the absorption and the emission spectra of all molecules.
  
  
  RESULTS
  The trend of the calculated HOMO-LUMO gaps nicely compares with the spectral data. In addition, the estimated values of the open-circuit photovoltage (Voc) for these compounds were presented in two cases/PC60BM and/PC71BM.
  
  
  CONCLUSIONS
  The study of structural, electronics and optical properties for these compounds could help to design more efficient functional photovoltaic organic materials.
authors.affiliation: ECIM/LIMME, Faculty of Sciences Dhar El Mahraz, University Sidi Mohamed Ben Abdallah, Fez, Morocco.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Bourass
authors.affiliation: ECIM/LIMME, Faculty of Sciences Dhar El Mahraz, University Sidi Mohamed Ben Abdallah, Fez, Morocco.
authors.forename: Adil Touimi
authors.initials: AT
authors.lastname: Benjelloun
authors.affiliation: ECIM/LIMME, Faculty of Sciences Dhar El Mahraz, University Sidi Mohamed Ben Abdallah, Fez, Morocco.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Benzakour
authors.affiliation: ECIM/LIMME, Faculty of Sciences Dhar El Mahraz, University Sidi Mohamed Ben Abdallah, Fez, Morocco.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Mcharfi
authors.affiliation: Equipe d'Electrochimie et Environnement, Faculté des Sciences et Techniques, University Moulay Ismaïl, Meknes, Morocco.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Hamidi
authors.affiliation: Equipe d'Electrochimie et Environnement, Faculté des Sciences et Techniques, University Moulay Ismaïl, Meknes, Morocco ; Centre Régional des Métiers d'Education et de Formation, BP 8, Errachidia, Morocco.
authors.forename: Si Mohamed
authors.initials: SM
authors.lastname: Bouzzine
authors.affiliation: ESTM, (LASMAR), University Moulay Ismaïl, Meknes, Morocco.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Bouachrine
keywords: Optoelectronic properties; Organic solar cells; TD-DFT; Thienopyrazine derivatives; Voc (open circuit voltage); π-conjugated molecules