Dye-modified ZnO nanohybrids: optical properties of the potential solar cell nanocomposites

We report the hybridization of ZnO with natural dyes [Laali, Zobo] or synthetic dye [methyl red] forming ZnO–laali, ZnO–zobo and ZnO–methyl red nanocomposites in bright colours. The structural, optical and dye photosensitization influence of the hybrid nanocomposites were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), UV–Visible absorption spectroscopy and photoluminescence (PL). The surface plasmon absorption band of ZnO–laali and ZnO–zobo shifts towards red and blue, respectively, with significantly enhanced absorption intensities, indicating the interaction and optical influence of the respective dyes in photosensitization. Optical and absorption character of ZnO methyl red and bare ZnO are similar indicating the insignificant effect of methyl red on photosensitization. PL spectra of ZnO–laali and ZnO–zobo display enhanced UV light emission due not only to the surface electron transfer from their respective inherent isoplumbagin and anthocyanin to ZnO but also to the extension of the Fermi energy level to the ZnO. Dyes adopted influence the optical band gaps of the evolved hybrid nanocomposites.