Efficient charge transfer in solution-processed PbS Quantum Dot-reduced graphene oxide hybrid materials

TL;DR

This study develops a covalent-linking method to create PbS and other quantum dot-reduced graphene oxide hybrids, demonstrating efficient charge transfer suitable for optoelectronic applications.

Contribution

A versatile covalent-linking approach for functionalizing reduced graphene oxide with various quantum dots, enabling controlled hybrid dispersions with high charge transfer efficiency.

Findings

Achieved well-controlled QD coverage on rGO sheets.

Demonstrated up to 95% electron transfer efficiency.

Tunable transfer efficiency with core/shell QDs.

Abstract

Quantum dot - graphene hybrid materials have raised 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 application in light harvesting and opto-electronic devices. Here 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 size and composition (PbS, PbS/CdS and CdSe QDs), and shape (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 up to 95%, together with subtle graphene Raman G-band shifts upon QD linking, supports 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.