Effect of TiO₂ nanoparticles on newly synthesized phenothiazine derivative-CPTA dye and its applications as dye sensitized solar cell

In this paper, effect of titanium dioxide (TiO₂) nanoparticles (NPs) on newly synthesized phenothiazine dye i.e., (Z)-2-cyano-3-(10-heptyl-10H-phenothiazin-7-yl) acrylic acid (CPTA dye) has been studied using spectroscopic techniques such as absorption, fluorescence and electrochemical. Absorption spectra of CPTA dye in the presence of TiO₂ appears broadened without any shift in the absorption peaks which suggests possible interactions between the CPTA dye and TiO₂ NPs and absence of complex formation. These inferences were validated by determining association constant (k_a) according to Benesi–Hildebrand theory. In order to see the role of fluorescence quenching, S-V theory was invoked, it was observed that phenomenon of quenching follows dynamic or collisional process under both steady and transient states. Experimentally determined magnitude of bimolecular quenching rate parameter is equal to the order of maximum collisional quenching rate parameter. Role of energy transfer between CPTA dye and TiO₂ NPs has been discussed using Rehm-Weller theory. From this it reveals that electron transfer process is more pronounced under more polar solvent (Methanol) than less polar solvent (ethyl acetate). Electron transfer mechanism has been exploited in solar energy harvesting applications by fabricating solar cell sensitized by CPTA dye. From this, it was observed that the efficiency and fill factor of fabricated DSSC was 2.15% and 0.58 respectively under optimized conditions and solar harvesting property of newly synthesized phenothiazine derivative of CPTA dye is the first report.