Synthesis, characterization and theoretical studies of the photovoltaic properties of novel bifunctional reactive disperse dyes based on aminothiazole derivatives

Abstract

This article comprises synthesis and characterization of two polyfunctional diazo reactive-disperse dyes with aminothiazole moiety for application in dye-sensitized solar cells (DSSC). The characterization techniques employed were Gas chromatography-mass spectrometry (GC-MS), Fourier-transform infrared spectroscopy (FT-IR), Ultraviolet-visible spectroscopy (UV-vis), and Nuclear magnetic resonance (NMR) to determine the different functional groups, molecular connectivities and molecular weight of the various fragments of the synthesized dyes. Theoretical Density Functional Theory (DFT) and Time-Dependent TD-DFT calculations were performed using B3LYP/6-311+g(d,p). It can be observed that the HOMO energy levels of the respective dyes have lower values than I−/I3− redox couple level (around -4.80 eV) in the four different phases studied, which is crucial for the regeneration of the oxidized dye molecule and efficient charge separation. Furthermore, the HOMO-LUMO energy gaps of DYES F and S are within the range 2.38-5.40 eV, where all LUMO-CB of TiO2 energy gap values are sufficient for generating enough driving force for effective electron injection. The promising results of Light-harvesting efficiency (LHE) (values ranging from 0.81 to 0.89 except for DYE S in chloroform phase where it has an unusual value of 0.21) and Open-circuit voltage (VOC) values gotten compared with other organic, and natural sensitizers were due to the better interaction between the carboxyl and carbonyl groups of aryl azo molecule joined to the thiazolyl nucleus and the surface of TiO2 permeable film. DYE S exhibits the lowest band gap (2.374eV), which designates the highest chemical activity of the two dyes. Results from the quantum theory of atoms-in-molecules indicate that DYES F and S exhibit additional stability due to their relatively high H-bond interactions as well as certain additional intra-atomic bonds among the atoms of the investigated compounds. The outcome of the Natural bond orbital (NBO) analysis suggests that the strongest charge transfer occurs in DYE S as compared to DYE F. The types and modes of excitations for the first five excited states of the synthesized dyes were observed from the results of the hole-electron excitation analysis. First hyperpolarizability values of the dye F and dye S were determined to be 47.24 and 46.90 times the hyperpolarizability value of urea, demonstrating its excellent non-linear optical (NLO) response.