Upconverted Nanophosphors for Increasing Efficiency in a Dye-Sensitized Solar Cell
Yogendra Nath Chouryal, Rahul Kumar Sharma, Neeraj Tomar, Neelam Yadav, Heera Lal Kewat, Ishfaq Abdullah Wani, Sandeep Nigam, Praveen K. Surolia, Sri Sivakumar, Pushpal Ghosh
Abstract
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.