Oct 30, 2009
Thin film provides simple white-light solution
Hybrid ZnO/organic heterostructure thin films have grabbed the attention of LED developers by combining the stable optical properties of ZnO with the simple processing requirements of organic materials. ZnO/organic heterostructures that operate in the green to yellow or blue-UV region have been observed, while white-light electroluminescence from ZnO/organic heterostructures has remained out of reach.
As reported recently in the journal Nanotechnology, researchers from National Taiwan University have come up with a convenient and low-cost way of fabricating ZnO/organic heterostructure white-light emitting devices. The team uses a hydrothermal method with a modified seeding layer to grow a ZnO nanorod (NR) array on a polyfluorene (PF) thin film, forming a p-n junction heterostructure.
The group's white-light emitting device exhibits a broad emission band covering the entire visible range from 400 to 800 nm. The white-light electroluminescence is attributed to the greatly enhanced green-yellow emission associated with the ZnO surface defects in the ZnO NR array/PF heterostructure and the blue emission from the PF. The enhancement of the ZnO-defect emission is caused by the presence of Zn(OH)2 at the interface between the ZnO NRs and the PF layer.
The study highlights that ZnO nanorod array/PF heterostructures offer a straightforward approach to making white-light electroluminescence devices that take advantage of the high carrier mobility of inorganic materials and the high luminescence efficiency of organic materials at very low cost.
About the author
The work was performed at the National Taiwan University (NTU) of Taiwan. Ching-Fuh Lin is a professor in the Graduate Institute of Photonics and Optoelectronics, Graduate Institute of Electronics Engineering and Department of Electrical Engineering, National Taiwan University. He has published around 120 journal papers, 280 conference papers and 30 issued patents. His current research interests include thin-film solar cells, silicon-based light-emitting devices, nano-structures for optoelectronics, and ultrafast phenomena and carrier dynamics in semiconductor lasers/amplifiers, broadband semiconductor lasers/amplifiers for optical communication. Prof. Ching-Fuh Lin is a member of Asia-Pacific Academy of Materials, a senior member of the IEEE Lasers and Electro-Optics Society and a member of the Optical Society of America. Chun-Yu Lee is a PhD student in Lin's group at NTU. This work was financially supported by the National Science Council, Taiwan, Republic of China (NSC96-2221-E-002-277-MY3, NSC97-2218-E-002-013, and NSC97-2221-E-002- 039-MY3).