Opaque Layer Improves Light Output

Attempting to improve an organic LED's light output by covering its top with an opaque, 50-nm-thick layer of silver may seem a little nonsensical, but the technique has allowed researchers at the University of Rochester in New York to increase the observed photoluminescence intensity tenfold. The silver transfers molecular fluorescence from the LED's inner layers by coupling radiation from the metal's interior surface plasmon mode to its exterior surface plasmon mode. As reported in the May 20 edition of Applied Physics Letters, the researchers assured resonance in the coupling and in the emission of fluorescence into free space by constructing the silver and LED layers in a grating pattern.