Emissive ZnO–graphene quantum dots for white-light-emitting diodes

• Published in: Nature nanotechnology Vol. 7; no. 7; pp. 465 - 471
• Main Authors: Son, Dong Ick, Kwon, Byoung Wook, Park, Dong Hee, Seo, Won-Seon, Yi, Yeonjin, Angadi, Basavaraj, Lee, Chang-Lyoul, Choi, Won Kook
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-07-2012; Nature Publishing Group
• Subjects: 639/624/1020; 639/925/357/1017; 639/925/357/551; Chemical synthesis; Chemistry and Materials Science; Electrons; Emissions; Fuel cells; Fuel technology; Graphene; Graphite; Graphite - chemistry; Light; Light emitting diodes; Luminescence; Materials Science; Nanocomposites; Nanotechnology; Nanotechnology - methods; Nanotechnology and Microengineering; Particle Size; Photovoltaic cells; Photovoltaics; Physics; Quantum Dots; Sensors; Zinc Oxide - chemistry
• ISSN: 1748-3387; 1748-3395
• DOI: 10.1038/nnano.2012.71

Hybrid nanostructures combining inorganic materials and graphene are being developed for applications such as fuel cells, batteries, photovoltaics and sensors. However, the absence of a bandgap in graphene has restricted the electrical and optical characteristics of these hybrids, particularly their emissive properties. Here, we use a simple solution method to prepare emissive hybrid quantum dots consisting of a ZnO core wrapped in a shell of single-layer graphene. We then use these quantum dots to make a white-light-emitting diode with a brightness of 798 cd m
−2
. The strain introduced by curvature opens an electronic bandgap of 250 meV in the graphene, and two additional blue emission peaks are observed in the luminescent spectrum of the quantum dot. Density functional theory calculations reveal that these additional peaks result from a splitting of the lowest unoccupied orbitals of the graphene into three orbitals with distinct energy levels. White emission is achieved by combining the quantum dots with other emissive materials in a multilayer light-emitting diode.
Quantum dots with a zinc oxide core and a strained graphene shell are used as an emissive layer in a white-light-emitting diode.