Abstract
The need for light weight, low-power color displays and backlights has spurred interest in thin-film, organic electrolumi nescent (EL) devices. A typical small-molecule organic thin-film light-emitting diode (LED) consists of an indium-tin oxide (ITO) anode on a glass substrate followed by sequential layers of bis(triphenyl)diamine (TAD, hole transporter), tris(8-hydroxyquinoline)aluminum (AIQ, electron transporter and green light-emitter), and a low work function metal cathode (e.g., A1 or Mg:Ag). This paper describes a microcavity organic LED, which has enhanced spatially integrated (~2) and forward (>3) surface-emitted intensity, and which could be suitable for low- information content display applications. The device, shown in Fig. 1, employs an optical microcavity to enhance the efficiency of a nearly monochromatic organic light-emitting diode. Assuming the internal light emission is isotropic, the fraction of light that escapes from an LED is limited by total internal reflection and given by the factor l/2n2,1 where n is the refractive index of the emissive layer. We can enhance to total escaping fraction or the intensity in the forward direction by tuning the cavity resonance wavelength relative to the molecular emission wavelength.
© 1996 Optical Society of America
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