Portland, Ore. -- Organic LEDs promise to enable "spray on" displays covering entire walls and conforming to almost any form factor. But OLEDs' lower efficiency makes them dimmer and lower in contrast than conventional, inorganic LEDs. Now a chemist and an EE at the Massachusetts Institute of Technology claim to have hit upon a solution that increases OLED efficiency to 85 percent from 25 percent.
EE professor Marc Baldo approached chemistry professor Troy Van Voorhis last year for help in figuring out why only a quarter of the electrons and holes injected into OLEDs recombine. Van Voorhis surmised from detailed simulations of OLEDs that their electrons have mostly the same spin. Since electrons and holes can only recombine to emit photons if their spins are opposite, Van Voorhis recommended doping with a heavy metal.
Baldo confirmed Van Voorhis' solution experimentally, achieving 85 percent recombination.
The David and Lucile Packard Foundation recently awarded Van Voorhis an unrestricted research grant of $625,000 over five years. The professor plans to apply it to organic-semiconductor research. "In organic LEDs, electrons are the glue that holds their molecules together, so we want to improve our understanding of how they behave," he said.