A synergistic effect of NaYF4:Yb,Er@NaGdF4:Nd@SiO2 upconversion nanoparticles and TiO2 hollow spheres to enhance photovoltaic performance of dye-sensitized solar cells

Introducing upconversion nanoparticles (UCNPs) or fabricating TiO2 hollow spheres (TiO2-HSs) are considered two feasible strategies to enhance the photovoltaic performance of dye-sensitized solar cells (DSSCs). However, studies investigating a combination of UCNPs and TiO2-HSs for the application in DSSCs are still scarce. In this contribution, NaYF4:Yb,Er@NaGdF4:Nd@SiO2 UCNPs and TiO2-HSs were synthesized and respectively applied as upconversion layers and scattering layers on the TiO2 photoanode of DSSCs. The influence of different doping ratios of UCNPs on cell performance was explored. The present results reveal that the DSSCs device based on conventional P25 photoanode films incorporating the UCNPs with 10% can achieve a photovoltaic efficiency of 6.65%, showing 29.63% enhancement in comparison to the device without UCNPs. When the TiO2-HSs are used as scattering layers above the P25 film, the DSSCs device obtains a higher photovoltaic efficiency of 6.97%. More importantly, combining the UCNPs and TiO2-HSs can further enhance the photoelectrical property of DSSCs, realizing an optimal efficiency of 8.17%. Such an improvement can be attributed to a synergistic mechanism arising from the upconversion effect of UCNPs and the light scattering effect of TiO2-HSs. This work opens a new way of preparing composite photoanode films to improve the photovoltaic performances of DSSCs.