Nov 17, 2009
Nanowire sheet has flexible LED applications covered
Nanomaterials and display experts from Ajou University in Korea have developed a facile process to fabricate ZnO/organic hybrid LEDs based on a paper-like ZnO sheet that consists of mass-produced ZnO nanowires. The use of thin free-standing ZnO-nanowire sheets opens up the possibility to fabricate flexible LEDs that operate at either ultraviolet or visible wavelengths at low cost.
First, the researchers synthesized a ZnO-nanowire product with a cotton-like appearance under ambient atmospheric conditions by using a vapour-phase growth method. Next, the mass-produced ZnO nanowires were transformed into flexible thin sheets by a simple dispersion-and-filtration method. Notably, the synthesis of ZnO nanowires can be easily scaled up to industrial levels and the production of ZnO-nanowire sheets requires only inexpensive equipment. Simple mechanical pressing of a ZnO-nanowire sheet against a film of p-type organic semiconductor is all that is required to make a hetero-junction for a hybrid LED. A number of p-type organic semiconductor materials were used and the corresponding electroluminescent spectra were investigated.
As well as demonstrating a novel way to fabricate ZnO/organic hybrid LEDs, the study provides an insight into the defect-related electroluminescence from the ZnO-nanowire sheets. Currently, the ultraviolet emission, which is the characteristic of crystalline ZnO, is weak compared with the defect-related visible emission.
Opportunities for improving the performance of the hybrid LEDs include modifying the emission properties of ZnO nanowires through the control of defects, and the decoration of the ZnO-nanowire surface by metal particles to take advantage of surface-plasmon effects.
Other potential applications for flexible ZnO-nanowire sheets include solar cells and sensors.
The group presented its results in the journal Nanotechnology.
About the author
Dr Jinzhang Liu is a research assistant professor working in the NMDID (Nano Materials and Devices for Information Display) group led by Prof. Soonil Lee at Ajou University in Korea. The group also includes Prof. Y H Ahn, Prof. Ji-Yong Park and Prof. Ken Ha Koh who are working on the synthesis, characterization and application of nano-sized materials and devices.