Effective Upconverter and Light Scattering Dual Function LiYF₄:Er³⁺/Yb³⁺ Assisted Photoelectrode for High Performance Cosensitized Dye Sensitized Solar Cells

Conversion of near-infrared (NIR) light photons into visible light has remarkable advantages in dye sensitized solar cells (DSSCs) for their improved performance. This study uncovers the dual function of LiYF4:Er3+/Yb3+ as upconverter (UC) and light scattering material in DSSCs by its incorporation onto the photoelectrode. The LiYF4:Er3+/Yb3+ powders were prepared using a facile hydrothermal process followed by spin deposition of LiYF4:Er3+/Yb3+ suspensions over photoelectrode. The photoelectrode used for this investigation was further cosensitized with N719 and squaraine SPSQ2 dyes. The dual functions of LiYF4:Er3+/Yb3+ material coupled with dye cosensitization treatment produced record power conversion efficiency (PCE) of 10.53% in the fabricated DSSC. The LiYF4:Er3+/Yb3+ enabled the photoelectrode DSSC to exhibit good short-circuit current density (Jsc) of 22.16 mA/cm2, open-circuit voltage (Voc) of 0.66 V, and fill factor (FF) of 0.72. This work is the debut attempt toward the application of a photoelectrode embedded with dual function and cosensitized materials to utilize lower energetic photons through the upconversion mechanism and improve absorption close to red wavelengths (absorption band 630–700 nm) through the dye cosensitization process.