New organic compounds based on N-fluorene-carbazole moiety for dye-sensitized solar cells. Computational study.

Abstract

In this work we are interested to the theoretical study of new organic dyes comprising N-fluorene-carbazole moiety as an electron-donating group, several unit based on thiophene (Th), dithiophene (2Th), 3.4-ethylenedioxythiophene (EDOT), dithienothiophene (DTT) or 4-dicyanomethylene-4H-cyclopenta [2.1-b; 3-4-b']-dithiophene (CDM) and 4H-cyclopenta [2.1-b; 3.4-b']-4-dithiophene sulfone (CPDS) as π-spacer and a cyanoacrylic acid as the anchoring group in the molecular framework. For identical  electron donor groups, we introduced different π-spacer to examine their effect on the structural and electronic properties This study was performed by the density functional theory (DFT) method at B3LYP level the 6-31G(d,p). The HOMO, LUMO, band gap energy, ionization potentials (IPs), electron affinities (EAs) of these dyes has been calculated and reported in this paper. The electronic absorption and emission spectra of these dyes are studied by Time-Dependent Density Functional Theory (TD-DFT) calculations. Our aim is first to confirm and improve properties of these studied dyes. Second, to explore their electronic and spectroscopic properties on the basis of the DFT quantum chemical calculations. Third, to elucidate the parameters that influence the photovoltaic efficiency toward better understanding of the structure–property relationships. We think that the presented study of structural, electronic and optical properties for these dyes could help to design more efficient functional photovoltaic organic materials.