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.

Next steps

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.