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Chlorine Found to Boost Flat Panel Display Technology

L to R: Zhibin Wang, Zheng-Hong Lu, and Michael Helander hold their chlorine-enabled OLED devices (Univ. of Toronto)

L to R: Zhibin Wang, Zheng-Hong Lu, and Michael Helander hold their chlorine-enabled OLED devices (Univ. of Toronto)

Materials scientists at University of Toronto in Canada have found a simple way to use chlorine to reduce the complexity of Organic Light-Emitting Diode (OLED) devices and improve their efficiency. The faculty/student team published their findings in this week’s issue of the journal Science (paid subscription required).

OLEDs are used in a wide variety of devices, such as flat-panel display televisions, and for room lighting. They consist of a series of organic thin films between two conductors, which when electrical current is applied, emits a a bright light.

Toronto Ph.D. candidates Michael Helander and Zhibin Wang, with materials science and engineering professor Zheng-Hong Lu, devised a method of adding a one-atom thick film of chlorine to the surface of indium tin oxide, a standard electrode material found in today’s flat-panel displays. By adding the chlorine layer, the researchers created a medium that makes the electrical current through the OLED more efficient, eliminating the need for several layers required in traditional OLED devices.

While chlorine is a commonly used element in swimming pools and drinking water, chlorine gas itself has long been considered a dangerous substance; as far back as World War I, it was used as a chemical warfare agent. The Toronto team’s process, adds chlorine without resorting to its gaseous form. “We developed a UV [ultraviolet] light-assisted process to achieve chlorination,” says Helander, “which negates the need for chlorine gas, making the entire procedure safe and reliable.”

With traditional OLEDS, device makers need to trade-off brightness for efficiency; as brightness increases, efficiency declines. The Toronto researchers, however, found the efficiency of their chlorinated green-emitting OLEDs more than doubled at very high brightness.

Reducing the complexity of OLEDs — removing the need for multiple film layers — can also simplify manufacturing processes, which can lead to lower production costs. “This effectively lowers barriers for mass production,” says Zheng-Hong Lu, “and thereby accelerates the adoption of OLED devices into mainstream flat-panel displays and other lighting technologies.”

Read more: Researchers Improve Efficiency of LED Lighting

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