Enhanced efficiency of low-temperature fabricated dye-sensitized solar cells by incorporating upconversion nanoparticles

Abstract

Upconversion nanoparticles (UCNPs) can effectively assist solar cells in utilizing near infrared through the anti-Stokes’ emission mechanism. We incorporate UCNPs, for the first time, into the mesoporous TiO2 of dye-sensitized solar cells (DSSCs) in a low-temperature fabrication process. The mesoporous TiO2 is designed as a two-layer structure, where the lower layer is prepared from reactive anatase TiO2 chelated by acetic acid (h-TAc). The UCNP incorporation into the lower layer displays a significant improvement in photovoltaic performance. For an optimized UCNP incorporation, the power conversion efficiency (PCE) of the DSSCs can increase from 6.49 to 7.98%, an enhancement of 23%, further exceeding most of the improvement on low-temperature fabricated DSSCs reported in the literature. The enhanced PCE may be ascribed to the increase of photocurrent. We find that the hydrophobic UCNPs reveal better enhancement than hydrophilic UCNPs due to the prevention from the electrolyte penetration. However, the hydrophobic UCNP incorporation may cause the cracking of the mesoporous TiO2 layer. The strong bonding ability of h-TAc effectively alleviates the cracking issue.