Reflections on Polymers

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Date: July 9, 1999
From: Science(Vol. 285, Issue 5425)
Publisher: American Association for the Advancement of Science
Document Type: Brief article
Length: 1,029 words

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A decade ago, it was discovered that semiconducting organic polymeric materials could be made into light-emitting diodes (LEDs) (1). When electrons and holes injected into a suitable polymer capture each other, they form an exciton, which can then decay to produce a photon--light. Despite continuing controversy over some of the details of exciton generation and recombination, so much progress has been made that Philips Components now has a pilot-scale production plant aiming for polymers to take part of the estimated $40 billion per year displays market. The properties of the emitted light can be controlled by placing the polymer layer between two mirrors to form a tiny cavity, known as a microcavity. To date, inorganic materials have been used to make these mirrors (2). Now, Ho and colleagues (3) show on page 233 of this issue that control of the emitted light can be achieved using layered structures of semiconducting organic polymers.

The attraction of these semiconducting organic materials is twofold. First, at the molecular level their composition may be readily controlled to adjust their charge-transport properties (4) and the color of their emission (5), both of which are vital for commercially viable display devices. Second, these tunable polymers can be processed in solution. It has recently been shown that organic LEDs can be produced by ink-jet printing (6) and spin cast onto flexible substrates (7), emphasizing the potential their easy processing confers. Many of the organic LEDs studied to date are composite optical microcavity structures (8).The light-emitting polymer is confined to a thin (~100-nm) layer sandwiched...

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Gale Document Number: GALE|A55266731