Graphene quantum dot antennas for high efficiency Förster resonance energy transfer based dye-sensitized solar cells

The light harvesting efficiency of an acceptor dye can be enhanced by judicious choice and/or design of donor materials in the Förster resonance energy transfer (FRET) based dye-sensitized solar cells (DSSCs). In this work, we explore graphene quantum dots (GQDs) as energy relay antennas for the high power conversion efficiency Ru-based N719 acceptor dyes. The absorption, emission, and time decay spectral results evidence the existence of the FRET, the radiative energy transfer (RET), and a synergistic interaction between GQDs and N719 dye. The FRET efficiency is measured to be 27%. The GQDs co-sensitized DSSC achieves an efficiency (ƞ) of 7.96% with a Jsc of 16.54 mAcm−2, which is 30% higher than that of a N719-based DSSC. GQDs also reduce the charge recombination, which results in an increased open-circuit voltage up to 770 mV. The incident photon-to-current conversion efficiency and UV-Vis absorption measurement reveal that the enhanced absorption of the GQDs antennas is responsible for the improved Jsc in the whole UV-Visible region, while the RET/FRET and the synergistic effect contribute to the significant increase of Jsc in the UV region.