Improved Power Conversion Efficiency of Dye-Sensitized Solar Cells by Fluorophore-Assisted Spectrum Down-Conversion

Abstract

Effects of fluorophore-assisted spectrum down-conversion on the photovoltaic performance of dye-sensitized solar cells (DSSCs) are investigated in terms of fluorophore concentration, doping time, and thickness of TiO2 nanocrystalline film. The fluorophore doped in the TiO2 nanocrystalline film absorbs ultraviolet (UV) light and re-emits green light for more efficient light harvesting of N719 dye by means of Förster resonance energy transfer (FRET). Power conversion efficiency (PCE), incident photon to current conversion efficiency (IPCE), electrochemical impedance spectrum (EIS), and dark current are measured. Experimental results show that IPCE is enhanced for the DSSCs doped with the fluorophore and therefore the PCE. The doping of fluorophore into the DSSC can also strategically reach thinning of the TiO2 nanocrystalline film to prevent potential stress issue and reduce the amount of expensive dye. The DSSC fabricated with a 6.1-μm-thick TiO2 nanocrystalline film retains a high PCE of 8.63% by doping fluorophore into the DSSC, which is comparable to that (8.55%) fabricated with a TiO2 nanocrystalline film of a typcial thickness of 14 μm.