Microwave assisted structural engineering on efficient eco-friendly natural dye alizarin for dye sensitized solar cells application

Abstract

The novel eco-friendly natural dyes, (9E, 10E), − 9, 10-bis(2-(4-nitrobenzylidene) hydrazono) − 9,10 dihydroanthracene-1,2-diol (NHA) have been synthesised using the one-pot microwave-assisted solvent evaporation method, and physicochemical characterizations were carried out using 1H NMR, 13C NMR, GC-MS, and FT-IR data. The photophysical properties of NHA dye were determined using experimental and theoretical techniques. The Stoke’s shift shows a large bathochromic shift in polar solvents, which is due to the π→π * transition. The ground-state optimization of NHA dye was carried out using density functional theory (DFT) with the B3LYP/6–31 G level basis set. The HOMO-LUMO and energy band gap values computed from density functional theory and absorption threshold wavelengths are good agreement with each other. Further, the effect of TiO2 nanoparticles on NHA dye has been studied using spectroscopic and electrochemical techniques. It was observed that, NHA dye showed fluorescence quenching in the presence of TiO2 NPs, which is due to the photo induced electron transfer process. The apparent association constant of the interaction between NHA dye and TiO2 nanoparticles is also calculated using the Benesi-Hildebrand model. The Rehm-Weller relation infers that thermodynamically favourable electron transfer takes place between dyes and TiO2 NPs. Further, the solar cell was constructed using NHA dye as a sensitizer, and the photovoltaic conversion efficiency was found to be 1.16%.