Spectrally narrowed edge emission from organic light-emitting diodes

A dramatic spectrally narrowed edge emission (SNEE) from small molecular organic light-emitting diodes at room temperature, with a full width at half maximum of 5-10 nm, is described. The results show that this emission is due to irregular waveguide modes that leak from the indium tin oxide anode to the glass substrate at a grazing angle. Measurements of variable stripe length devices exhibit an apparent weak optical gain, but there is no observable threshold bias associated with this SNEE. Hence this apparent "optical gain" is suspected to result from misalignment of the propagating leaky waveguide mode and the collecting optics. (c) 2007 American Institute of Physics.