Imagine flat screen displays on materials so resilient that they can be rolled up and carried around, or moving images on clothing and newspapers that can be changed and updated. These applications may be a few years ahead, but with the research being undertaken in the lab of Professor Zheng-Hong Lu of the Department of Materials Science and Engineering, there can be no doubt that a revolution in display technologies is underway.
The current hallmark of display technology is the conventional light emitting diode (LED), which uses inorganic (without carbon) semiconductor materials containing very ordered crystalline structures. The main roadblock, according to Professor Lu, is that these materials often contain more than one crystalline material. The two materials must have crystal structures that match, so that impurities are not created at the interface between them. This effectively limits the area of the resultant display, after which size they become highly brittle.
In order to get around this brittleness, Lu and his team had to find a more robust material. “The most stable nano [extremely small] material in nature is the molecule; so naturally occuring nanomaterial, which is the molecule, for [electrical and light] applications, that’s really the focus of my research.” Organic molecules in fact are the most flexible material that can be grown on thin substrates.
The basic way in which Lu’s new FOLEDs (Flexible Organic Light Emitting Devices) function is that negative and positive charges are transported from a contact point through the molecule to a point where they recombine, releasing light. His research centres on producing FOLEDS for flat panel displays and general lighting. He is also studying fiber optic communications.
“Using molecular LEDs, the molecules are so resilient, robust, that you can coat this molecule on any substrate including plastic, so you can fold [the substrate] and you can make large area display applications” says Professor Lu. He explains that this technology may one day replace LCDs (liquid crystal displays) and allow much larger, thinner, lighter, flat panel displays.
The soft polymer substrates could be folded and rolled up for portability, and could contain curves or angled surfaces. Lu explains that space industries may find important applications from his new technology. These include thinner, lighter solar cells that could be rolled up to increase portability, and displays inside the space shuttle, which would also be thinner and could be curved to save room. Xerox is currently working on a similar technology for an application known as an electronic newspaper, where portable displays update the headlines instantly.
Brian Fong is a fourth year engineering science student working in the lab. He uses an instrument known as a FOLED Cluster Tool to evaporate the FOLED material and condense it on top of the substrate.
Fong is extremely excited about the work he is doing and the possible revolution it may help spurn, citing examples of current applications already underway. Kodak has already introduced a digital camera using a FOLED display, while Sony Corp. will begin manufacturing full-colour FOLED display panels for cell phones in the spring.
