Uniform β-NaYF(4):Er(3+)/Yb(3+) hexagonal nanoplatelets were synthesized via a modified hydrothermal route, and the nanoplatelets were applied as an external, bifunctional layer in a novel DSC configuration consisting of only one internal TiO(2) transparent layer. Approximately 10% enhancements of photocurrent and overall DSC efficiency are demonstrated by the addition of the external layer, which exhibits two functions of light reflecting and near-infrared (NIR) light harvesting. The novel DSC configuration not only simplifies the DSC fabrication process but also eliminates charge recombination induced by the conducting up-converting nanocrystals when used internally thus opening the path for other more efficient up-converting nanocrystals to be designed and applied.