Enhanced Sunlight Harvesting of Dye-Sensitized Solar Cells Assisted with Long Persistent Phosphor Materials

TiO2 nanoparticle-based dye-sensitized solar cells (DSSCs) were modified by depositing a layer of a long-persistent phosphor, SrAl2O4:Eu2+,Dy3+, on top of the TiO2 nanoparticle layer to prepare working electrodes of the DSSCs. SrAl2O4:Eu2+,Dy3+ red-shifted the short UV wavelengths into the main absorption range of the dye commonly used in DSSCs. The SrAl2O4:Eu2+,Dy3+ layer also acted as a light-scattering layer to reduce the loss of visible light. Incident photon to current conversion efficiency measurements showed that the application of such phosphor materials enhanced light-harvesting. The open-circuit voltage was found to be higher in the modified DSSCs. The electrons produced by the SrAl2O4:Eu2+,Dy3+ particles contribute to the reduction of I-3(-) to I-, leading to a lower I-3(-) concentration in the electrolyte. This reduces the recapture of electrons injected in the conduction band of TiO2 by triiodide ions and promotes the open circuit voltage. The performance of the modified DSSC device was improved compared with the cell using a working electrode without this phosphor layer. An overall 13% improvement in conversion efficiency of modified DSSCs was achieved due to the presence of the phosphor layer.