Solar-to-Electric Performance Enhancement by Titanium Oxide Nanoparticles Coated with Porous Yttrium Oxide for Dye-Sensitized Solar Cells

摘要

TiO2-Y2O3 core-shell nanoparticles for dyesensitized solar cells (DSSCs) have been fabricated by a solvothermal technique. The heterostructure of TiO2 nanoparticles coated with porous Y2O3 is confirmed with transmission electron microscopy. The bonding of the Y2O3 coating on the TiO2 surface is quantitatively analyzed in terms of the Lifshitz- van der Waals and electrostatic contributions to the surface free energy of the particles. TiO2 and Y2O3 constitute a core-shell heterojunction because the Fermi levels merge; this increases the open-circuit voltage. Higher recombination resistances are obtained in DSSCs with porous Y2O3-coated TiO2 compared with those in the reference cells, indicating "backscattering" inhibition of the porous Y2O3 barrier on TiO2 nanoparticles. Moreover, smaller transport resistances and longer electron lifetimes are achieved in DSSCs with TiO2-Y2O3 core-shell nanoparticles. Compared with a reference cell, the VOC of a DSSC with a partial Y2O3 coating on the surface of the TiO2 nanoparticles improves from 683 to 738 mV and the Jsc from 14.15 to 15.35 mA·cm~(-2), whereas the conversion efficiency increases by 15.2%.