Density functional theory study on the electronic structure of Monascus dyes as photosensitizer for dye-sensitized solar cells

This work presents a theoretical study of electronic and redox properties of Monascus dyes using DFT and TDDFT with B3LYP/6-31+G(d,p) level. The dye properties in solvent environment were carried out with IEF-PCM(UAKS)/TDDFT/B3LYP/6-31+G(d,p) method. The ground and excited state oxidation potentials as well as electron injection from the dyes to semiconductor TiO2 are reported. The calculation shows that all of the dyes can potentially be good photosensitizers in DSSC. Their LUMOs lie over the Ecb of TiO2 and their HOMOs lie under the reduction potential energy of the electrolytes (I−/I3−) corresponding to ability of electron transfer from the dye excited state to TiO2 and charge regeneration after photooxidation process, respectively.

► Theoretical study of electronic, optical and redox properties of natural dyes from Monascus fungi.
► A first report in electronic, optical and redox properties of Monascus dyes.
► Used as sensitizer in DSSC at the highest conversion efficiency (2.3%) among other natural dyes except chlorophyll.
► Properties relevant to the photovoltaic performance of the DSSC and previous experiments.
► Results show matching HOMO and LUMO energy level to TiO2 conduction band and reduction potential of electrolyte.