Strongly modified emission from organic electroluminescent device with a microcavity

We demonstrate the improvements of directionality and intensity of light emission from the electroluminescent (EL) device with a Fabry-Perot microcavity. The improvements have been realized by applying a new idea: (1) an unsymmetrical emission spectrum, with a steep rise at shorter wavelength side, from the emitting region doped with quinacridone, and (2) a composite dielectric mirror including a thick indiumtin-oxide (ITO) conducting layer. The resultant microcavity EL device exhibited a single mode emission with pure green (full width at half-maximun, FWHM = 15 nm at 535 nm), and the emission intensity for normal direction (along the optical axis of the device) was significantly enhanced. The sharply directed emission exceeded 40 000 cd/m2 at a driving current of 800 mA/cm2, which was higher than that of a noncavity EL device.