Charge transfer effects in graphene-CdSe/ZnS quantum dots composites

摘要

Graphene possesses unique physical properties, due to its specific energy bands configuration, substantiallydifferent from that of materials traditionally employed in solid-state optoelectronics. Among the variety of remarkableproperties, strong field effect, high transparency in the visible-light range and low resistivity of graphene sheets are themost attractive ones for optoelectronic applications. Zero-dimensional colloidal semiconductor nanocrystals, known asquantum dots (QDs), attract immense attention in the field of photonics due to their size-dependent tunable opticalproperties.By combining these two types of nanomaterials together, we demonstrate the role of graphene as an efficientcharge transfer medium from- and to II-VI quantum dots. The optical excitation of II-VI quantum dots dispersed onsingle layer graphene results in an electron transfer from the nanocrystals to graphene. This is evidenced fromphotoluminescence imaging and confirmed by the electrical measurements on QDs-decorated single layer graphene fieldeffect transistors (SLG-FET). In the second part of this paper we demonstrate an efficient hole injection from grapheneinto QDs-layered nanocrystalline structures and the operation of the corresponding graphene-based quantum dot lightemitting diodes (QD-LED). We also benchmark graphene vs. indium-tin-oxide (ITO) based QD-LEDs in terms of deviceelectroluminescence intensity performance. Our experimental results show better hole injection efficiency for graphenebasedelectrode at current densities as high as 200 mA/cmsup2/sup and suggest single layer graphene as a strong candidate toreplace ITO in QD-LED technology.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.