Theoretical examination of efficiency of anthocyanidins as sensitizers in dye-sensitized solar cells

Abstract

Abstract The structural effects and electronic contributions of four anthocyanidins, cyanidin (Cy), delphinidin (Dp), malvidin (Mv) and pelargonidin (Pg), have been investigated to improve the efficiency of dye-sensitized solar cells (DSSCs), using density functional theory (DFT) calculate parameters such as frontier molecular orbitals (MOs), band gap energies, reactivity descriptors. MOs surfaces showed that titanium dioxide (TiO2) orbital was susceptible to nucleophilic attack. The highest occupied molecular orbital (HOMO) of terminal hydroxyl groups in dye was susceptible to nucleophilic attacks at different degrees. MOs of dye-semiconductor showed intramolecular charge transfer from dye to TiO2 upon photoexcitation of dye. Electronic properties of dyes showed maximum absorption transitions in this order Mv < Dp < Pg < Cy. Reactivity descriptors revealed relationship between light-harvesting-efficiency (LHE) and chemical hardness (η) for dye molecules in the order Cy < Pg < Dp < Mv. Cy-sensitized solar cell has the highest efficiency among anthocyanidins and this is in agreement with reported empirical report. Thorough understanding of the electronic factors that contribute to light absorption is necessary to select chromophores whose structural characteristics maximize the overall performance of the DSSCs.