Enhanced Photovoltaic Performance of Dye-Sensitized Solar Cells by Efficient Near-Infrared Sunlight Harvesting using Upconverting Y2O 3:Er (3+)/Yb (3+) Phosphor Nanoparticles.

We report the efficiency enhancement in dye-sensitized solar cells (DSSCs) using Er(3+)/Yb(3+)-co-doped Y2O3 (i.e., Y2O3:Er(3+)/Yb(3+)) phosphor nanoparticles, prepared by a simple and cost-effective urea-based homogeneous precipitation method, for efficient near-infrared (NIR) sunlight harvesting. Under the light excitation at a wavelength of 980 nm, the as-prepared samples exhibited strong upconversion emissions at green and red visible wavelengths. To investigate the influence of Y2O3:Er(3+)/Yb(3+) nanoparticles on the photovoltaic performance of DSSCs, the phosphor nanoparticles were incorporated into titanium dioxide films to form a composite photoelectrode. For the resulting DSSCs, the increased power conversion efficiency (PCE) of 6.68 % was obtained mainly by the increased photocurrent of J SC = 13.68 mA/cm(2) due to the light harvesting enhancement via the NIR-to-visible upconversion process (cf., PCE = 5.94 %, J SC = 12.74 mA/cm(2) for the reference DSSCs without phosphor nanoparticles), thus, indicating the PCE increment ratio of ~12.4 %.