Emissive ZnO-graphene quantum dots for white-light-emitting diodes.
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.
Interface Control Research Center, Future Convergence Research Division, Korea Institute of Science and Technology, Hwarangro 14 gil 5, Seoul, Korea.
Dong Ick
DI
Son
Byoung Wook
BW
Kwon
Dong Hee
DH
Park
Won-Seon
WS
Seo
Yeonjin
Y
Yi
Basavaraj
B
Angadi
Chang-Lyoul
CL
Lee
Won Kook
WK
Choi
D006108:Graphite / Q000737:chemistry*; D008027:Light; D049449:Luminescence; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D045663:Quantum Dots; D015034:Zinc Oxide / Q000737:chemistry*
D006108:Graphite; D015034:Zinc Oxide