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 I₃^– to I^–, leading to a lower I₃^– 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