Commercial Upconversion Phosphors with High Light Harvesting: A Superior Candidate for High‐Performance Dye‐Sensitized Solar Cells

Abstract

An efficient photoanode for dye‐sensitized solar cells (DSSCs) requires a particular feature of high light harvesting. Herein, a promising new type of upconversion phosphors (UCPs)‐TiO2 composite photoanode for enhanced light harvesting in DSSCs is designed, resorting to the use of commercial upconversion β‐NaYF4:Yb3+, Er3+ phosphors with submicrometer‐sized irregular shapes. The excellent light scattering coupled with an additional near‐infrared light‐harvesting effect of upconversion β‐NaYF4:Yb3+, Er3+ nanoparticles contribute to the greatly enhanced light harvesting. Meanwhile, the incorporation of such UCPs into photoanodes involves the aggravation of charge recombination at the interface of photoanode–electrolyte; this unfavorable influence is minimized via the coating of a thin TiO2 layer on UCPs. The successful balance of the competition between such positive and negative impacts results in an optimal weight ratio of 15% for UCPs/TiO2; the corresponding DSSC delivers a power conversion efficiency (PCE) up to 7.17%, much higher than that of 5.45% for the bare TiO2 nanoparticle‐based device. This study highlights the great contributions of commercial β‐NaYF4:Yb3+, Er3+ UCPs to the efficient light harvesting for enhanced photovoltaic performance of DSSCs.