Titanium mesh-supported "TiO2 nanowire arrays/Yb-Er-F tri-doped TiO2 up-conversion nanoparticles" composite structure: Designation for high efficient flexible dye-sensitized solar cells

Highlights: • Ti mesh-supported "TNWAs/YEF-TiO₂-UCNPs_xP25_1-x" composite was hydrothermally prepared. • The "TNWAs/YEF-TiO₂-UCNPs_xP25_1-x" composites fully flexible DSSCs were constructed. • YEF-TiO₂-UCNPs expanded the incident light utilization range of the flexible DSSCs. • "TNWAs/YEF-TiO₂-UCNPs_60%P25_40%" based flexible DSSC exhibited enhanced PCE of 5.54%. -- Abstract: Titanium (Ti) mesh-supported "TiO₂ nanowire arrays (TNWAs)/Yb-Er-F tri-doped TiO₂ up-conversion nanoparticles (YEF-TiO₂-UCNPs)" composite structures were prepared as photoanodes of the flexible dye-sensitized solar cells (DSSCs) by using hydrothermal and spin-coating approaches. The as-synthesized YEF-TiO₂-UCNPs which could enhance the absorption of N719 dyes by converting the near-infrared light to visible light exhibited better up-conversion luminescence properties than the YbEr co-doped TiO₂ up-conversion nanoparticles (YE-TiO₂-UCNPs). Moreover, the appropriate YEF-TiO₂-UCNPs could enlarge light harvesting range of the formed flexible photoanode and improved the photovoltaic performance of the DSSCs. Under the simulated solar irradiation of 100 mW cm⁻² (AM 1.5G), the flexible DSSC with a Ti mesh-supported "TNWAs/YEF-TiO₂-UCNPs_60%P25_40%" composite structure achieved a short-circuit current density (J_sc) of 12.81 mA cm⁻² and a power conversion efficiency (PCE) of 5.54%, showing improvements of 45.7% and 37.8% as compared with TNWAs/P25_100% (8.79 mA cm⁻², 4.02%), respectively.