Exploring dynamics of resonance energy transfer in hybrid Quantum Dot Sensitized Solar Cells (QDSSC)

Graphene based nanomaterials are known to provide new avenues to improve semiconductor based light harvesting devices. This work makes use of graphene quantum dots (GQD) to improve the efficiency of a CdSe Quantum Dot Sensitized Solar Cell (QDSSC) by Forster Resonance Energy Transfer (FRET) mechanism. FRET describes non-radiative energy transfer between two adjacent molecules typically in range from 1 to 10 nm with one molecule as donor and other molecule as acceptor. If the acceptor is in close proximity of the excited donor, then their dipoles align resulting in transfer of excitation energy from donor to acceptor. Here graphene quantum dot acts as the energy donor to enhance light harvesting of CdSe quantum dot which acts as an acceptor in the hybrid solar cell. The introduction of GQD increases the efficiency of CdSe sensitized QDSSC from 0.18 to 0.28% showing an efficiency enhancement of 55%. The improved efficiency is mainly attributed to the 46% increase in current density of the GQD-CdSe solar cell compared to the CdSe QDSSC. The increased performance of the QDSSC owes to the existence of non-radiative energy transfer (FRET) between GQD and CdSe evident from photoluminescence (PL) quenching and lifetime measurements. This FRET system of GQD(donor)-CdSe (acceptor) shows an energy transfer of 48.7% providing new insights for selective light harvesting of the solar spectrum which can be utilised for various potential applications in future.