Performance enhancement in dye-sensitized solar cells by utilization of a bifunctional layer consisting of core–shell β-NaYF4:Er3+/Yb3+@SiO2 submicron hexagonal prisms

Abstract

Highly uniform, monodisperse β-NaYF4:Yb3+/Er3+(NYFYE) up-conversion phosphor submicron hexagonal prisms coated with a SiO2 layer are synthesized via a hydrothermal route, forming a core–shell NYFYE@SiO2 crystallites. These crystallites are incorporated into TiO2 nanocrystalline porous film to act as a bifunctional layer and form a composite photoanode employed in dye-sensitized solar cells (DSSCs). The influences of different amount of the NYFYE@SiO2 on the performance of the composite photoanodes and DSSCs are investigated. Studies indicate that by adding NYFYE@SiO2 the light scattering, absorption and near-infrared light harvesting of the composite photoanode are significantly increased, resulting in the great enhancement in the short-circuit current density (Jsc) and photoelectric conversion efficiency (η) of the DSSCs. The optimal properties with an Jsc of 14.91 mA cm−2 and η of 7.28% are obtained in a DSSC with NYFYE@SiO2 content of 15 wt %, increasing significantly by 14% and 29%, respectively, in comparison with those of the DSSC with pure TiO2 photoanode. This significant enhancement in the performance of the DSSCs can be attributed to the enhanced light absorption due to the enhanced light scattering and near-infrared up-conversion of the NYFYE@SiO2 bifunctional layer in the photoanode of the DSSCs.