Upconverted Nanophosphors for Increasing Efficiency in a Dye-Sensitized Solar Cell

Upconverting nanoparticles has a significant potential to enhance solar cell efficiency as a “spectral converter”. Here, we report a phase pure, cubic, upconverting BaGdF 5:Er/Yb-doped nanocrystal accessible via ionic liquids that are combined with TiO 2 to apply as the absorption layer in a dye-sensitized solar cell (DSSC) as a potential technology to harvest solar energy. Bright-green (520 and 540 nm) and red (665 nm) emissions were observed due to transitions of 2 H 11/2 + 4 S 3/2 → 4 I 15/2 and 4 F 9/2 → 4 I 15/2, respectively. The experimental data for 540 and 665 nm emission bands of BaGdF 5:Er 3+ /Yb 3+ nanoparticles have been fitted with a straight line with a slope of ∼2, which confirms the two-photon absorption process. It is also found that not only the overall upconversion intensity but also the I G / I R ratio has a significant effect on device efficiency. Under 1 sun illumination, cells fabricated with the BaGdF 5:Er 3+ (1%)/Yb 3+ (10%)/TiO 2 absorption layer showed the highest photon conversion efficiency (PCE) of 7.75% with current density J sc = 15.9 mA/cm 2 . However, when only TiO 2 is used as the absorption layer, a much lesser PCE of 4.60% along with J sc = 9.6 mA/cm 2 is obtained. Almost a 68.47% enhancement in photon conversion efficiency and a significant increase in current density ( J sc ) (65.62%) for the BaGdF 5:Er 3+ (1%)/Yb 3+ (10%)/TiO 2 -based device compared to the bare TiO 2 cells promise the potential use of upconverting materials as a spectral converter in the DSSC and other solar cell devices.