Charge Separation in Graphene-Decorated Multimodular Tris(pyrene)-Subphthalocyanine-Fullerene Donor-Acceptor Hybrids

A new approach to probe the effect of graphene on photochemical charge separation in donor-acceptor conjugates is devised. For this, multimodular donor-acceptor conjugates, composed of three molecules of pyrene, a sub-phthalocyanine, and a fullerene C-60 ((Pyr)(3)SubPc-C-60), have been synthesized and characterized. These systems were hybridized on few-layer graphene through p-p stacking interactions of the three pyrene moieties. The hybrids were characterized using Raman, HRTEM, and spectroscopic and electrochemical techniques. The energy levels of the donor-acceptor conjugates were fine-tuned upon interaction with graphene and photoinduced charge separation in the absence and presence of graphene was studied by femtosecond transient absorption spectroscopy. Accelerated charge separation and recombination was detected in these graphene-decorated conjugates suggesting that they could be used as materials for fast-responding optoelectronic devices and in light energy harvesting applications.