Efficient charge transfer in solution-processed PbS quantum dot–reduced graphene oxide hybrid materials

Abstract

Quantum dot–graphene hybrid materials have attracted significant interest due to the unique synergy of the optical properties of colloidal quantum dots (QDs) and the transport properties of graphene. This stimulated the development of low-cost and up-scalable solution-processed strategies for hybrid materials with potential applications in light harvesting and optoelectronic devices. Herein, we report a versatile covalent linking-based approach for the functionalization of reduced graphene oxide (rGO), to prepare a variety of QD–rGO hybrid dispersions with QDs of different sizes and compositions (PbS, PbS–CdS and CdSe QDs), and shapes (CdSe–CdS dot-in-rods). We achieved a well-controlled QD coverage of the rGO sheets by functionalizing the rGO surface with mercapto-silane linkers. A further spectroscopic investigation of near-infrared PbS QD–rGO materials demonstrates efficient electronic coupling between both materials. The QD photoluminescence emission quenching and exciton lifetime shortening of up to 95%, together with subtle graphene Raman G-band shifts upon QD linking, support electron transfer as the dominant relaxation pathway from the QD to the rGO. The use of core–shell PbS–CdS QDs allows tuning of the transfer efficiency from 94% for a 0.2 nm thin CdS shell, down to 30% for a 1.1 nm thick shell.