Fluorescence resonance energy transfer of CaF2: Eu2+, Tb3+ applied to dye-sensitized solar cells.

CaF2: Eu2+, Tb3+ introduced into dye-sensitized solar cells (DSSCs) were studied to examine the influence of luminescent materials on photoanodes using a simple method. The emission spectra of CaF2: Eu2+, Tb3+ included the blue light of Eu2+ (4f → 5d) at 430 nm and green emission of Tb3+ (5D4 → 7F5) at 542 nm under the monitoring wavelengths at 398 nm, which matched well the absorption range of the N719 dye in DSSCs. Energy transfer (ET) was verified between Eu2+ and Tb3+ ions and the efficiency of ET found to increase with Tb3+ concentration. Both the fluorescence resonance and luminescence-mediated ETs between phosphor and N719 dye were observed as the main contribution in improving photocurrent and power conversion efficiency (PCE) of these DSSCs. The PCE of DSSCs doped with phosphors was greatly increased by 5.16, to 43.3%, which was comparable to cells made of pure TiO2 photoanodes. Moreover, CaF2: Eu2+, Tb3+ enlarged the surface area of TiO2 photonaodes, which helped the adsorption performance of the TiO2 film.