Selected organic dyes (carminic acid, pyrocatechol violet and dithizone) sensitized metal (silver, neodymium) doped TiO₂/ZnO nanostructured materials: A photoanode for hybrid bulk heterojunction solar cells

A photoactive nanohybrid material consisting of pyrocatechol violet, carminic acid and dithizone dyes functionalized silver and neodymium-doped TiO₂/ZnO nanostructured materials is reported here, as photoactive blend, for solid-state dye sensitized solar cell. First of all we synthesized metals (silver, neodymium) doped (TiO₂) Titanium oxide nanoparticles and their nanocomposites (TiO₂/ZnO, M−TiO₂/ZnO) using the sol–gel and reflux technique, respectively. The synthesized samples were then characterized by UV–Visible spectroscopy, X-Ray diffraction Analysis (XRD), Scanning electron microscopy (SEM), Energy dispersive X-Ray Analysis (EDX), and Fourier Transform infrared spectroscopy (FTIR). Optical studies were done through UV–Visible spectroscopy and the absorption spectra were used to calculate band gaps. The value of the energy gap for TiO₂ nanoparticles is 3.10 eV which was gradually tuned to 2.47 eV after incorporating metals (Ag and Nd) and forming respective nanocomposites. X-Ray diffraction Analysis (XRD) patterns revealed the purity and crystallinity in samples. Scanning electron microscopy (SEM) confirmed the irregular morphology (nanorods and spherical shaped) of ZnO and TiO₂ nanostructures respectively. The elemental composition of nanomaterials was successfully investigated using energy dispersive X-ray analysis (EDX). In the absence of any impurities, Fourier Transform infrared spectroscopy (FTIR) was used to identify the functional groups in synthesized material. For device fabrication, a solid-state electrolyte, P3HT, a hole conducting polymer was used. Characterization of fabricated solar cells was done using I-V measurements. Under simulated solar irradiation, the DSSC based on pyrocatechol violet sensitized neodymium doped TiO₂/ZnO nanohybrid materials exhibited the best PCE (power conversion efficiency) of 2.38 % and significantly improved Jsc (short circuit current density) of 15.68 mA/cm² as compared to carminic acid and dithizone in photovoltaic measurements. The improved power conversion efficiency of this device is ascribed to the particle size, increased dye adsorption, increased surface area and thus improved short circuit current density (Jsc).