Graphene–Ruthenium Complex Hybrid Photodetectors with Ultrahigh Photoresponsivity

The maximum responsivity of a pure monolayer graphene-based photodetector is currently less than 10 mA W(-1) because of small optical absorption and short recombination lifetime. Here, a graphene hybrid photodetector functionalized with a photoactive ruthenium complex that shows an ultrahigh responsivity of ≈1 × 10(5) A W(-1) and a photoconductive gain of ≈3 × 10(6) under incident optical intensity of the order of sub-milliwatts is reported. This responsivity is two orders of magnitude higher than the precedent best performance of graphene-based photodetectors under a similar incident light intensity. Upon functionalization with a 4-nm-thick ruthenium complex, monolayer graphene-based photodetectors exhibit pronounced n-type doping effect due to electron transfer via the metal-ligand charge transfer (MLCT) from the ruthenium complex to graphene. The ultrahigh responsivity is attributed t…