Enhanced Power Conversion Efficiency Using a Ce³⁺:SrF₂ Down-Shifting Nanophosphor-Based Photoelectrode for Dye-Sensitized Solar Cell Applications

A lanthanide-doped inorganic down-shifting nanophosphor that converts the intense ultra-violet (UV) light photons to visible-light photons is highly attractive for dye-sensitized solar cells (DSSCs) to enhance light harvesting and power conversion efficiencies. In the present research, for the first time, a highly luminescent Ce3+-doped SrF2 (Ce3+:SrF2) nanophosphor is employed as a down-shifting nanophosphor material in the photoanode of DSSC. The nanophosphor was synthesized by co-precipitation technique, followed by a rapid microwave calcination approach. The structural and morphological properties of the synthesized nanophosphor are investigated by X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy analyses. The optical absorption and emission characteristics of the Ce3+:SrF2 down-shifting nanophosphor are investigated. Interestingly, the nanophosphor displayed a broad luminescence in the visible region under UV wavelength excitation. Absorption studies show that the Ce3+:SrF2 nanophosphor absorbs the deep-UV and near-UV radiations, protecting the iodide electrolyte from thermal degradation. To further study the performance of the down-shifting layer in DSSC, the Ce3+:SrF2/TiO2 nanocomposite-based photoanodes were used to fabricate the DSSCs. As a result, the nanocomposite-based device has demonstrated an excellent photo-conversion efficiency of 8.8%. The improvement in the incident-photon-to-current efficiency curve and electrochemical values (Jsc = 15.2 mA cm–2, Voc = 0.82 V, and FF = 0.73) are due to the enhanced visible-light photon harvesting and high chemical stability.