Microwave-solvothermal synthesis of various TiO2 nano-morphologies with enhanced efficiency by incorporating Ni nanoparticles in an electrolyte for dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) have been fabricated with various nanostructured TiO2 morphologies, including interconnected beads-like (IBL), square platelets-like (SPL), spindle shape-like (SSL), and porous spheres-like (PSL), synthesized in different solvents (ethanol, mixture of ethanol + H2O and HF), and size and shape-tuned Ni-NCs of mixed triangular and hexagonal morphological crystals with sizes ranging from 15 to 62 nm in ethylene glycol (polyol) medium. These different TiO2 and Ni-NCs were constructed via a rapid, facile microwave-assisted solvothermal (MW-ST) route. The application potential of these TiO2 NCs as photoanodes unveiled excellent morphology-dependent PCEs (5.3% to 9.33%) using a conventional electrolyte and N719 dye as a photosensitizer. Subsequently, after impregnating Ni-NCs in the I−/I3− electrolyte, the nanoparticles on the surface of each TiO2 morphology acted as excellent scattering centers to provide a potential interface between TiO2 and Ni-NCs and enhance both light absorption and scattering, leading to improvements in the PCEs to 5.8%, 8.37%, 9.19% and 10.02% for the PSL, SSL, SPL and IBL-based photoanodes, respectively. This enhanced PCE was accomplished by systematic optimization of factors such as the surface morphology of the TiO2 photoanode and the size and concentration of the Ni-NCs in the electrolyte to attain the best advantages of scattering-induced effective light utilization and size-mismatching effects at the photoanode and Ni-NCs integrated electrolyte interface. The incorporated Ni-NCs effectively trap incident light and successively improve the rate of electron–hole pair formation and short circuit current (Jsc); they also exhibit excellent stability in the conventional I−/I3− electrolyte over a period of 30 days.