Theoretical investigation of electronic, optical and photovoltaic properties of alkylamine-based organic dyes as sensitizers for application in DSSCs

In the present work, eighteen organic sensitizers with Donor-π-Acceptor structure comprising a dialkylamine as electron donor was designed and studied. All dyes have a cyanoacrylic acid group as an electron acceptor and anchoring group to the TiO₂ electrode, while the π-linker was the thiophene group or benzene group. The effects of an elongation of the π bridge by the introduction of the anthracene on the performance of dye-sensitized solar cells (DSSCs) were reviewed. A particular interest is conferred to the impact of the length of the alkyl chain of the dialkylamine on the properties of the dyes. The impact of the nature of the junction of the anthracene the side of the donor and the side of the acceptor on the photovoltaic performances of the DSSC is analyzed and illustrated. Density Functional Theory (DFT) and Time Dependent-Density Functional Theory (TD-DFT) computations have been used to understand the structural, molecular, electronic and photophysical parameters of the dyes designed. This study conclude that the length of the alkyl chain of the dialkylamine has no effect on the values of E_HOMO, E_LUMO, E_g and λ_mₐₓ of the studied dyes. The results obtained showed that the introduction of anthracene into the π bridge of the dyes leads to a good performance. The best performing dyes are those in which the anthracene is triply or double bonded to the donor group and simply linked to the thiophene or to the benzene.