Manipulating the Microcavity Structure for Highly Efficient Inverted Top-Emitting Organic Light-Emitting Diodes: Simulation and Experiment

A comprehensive theoretical and experimental study on inverted top-emitting organic light-emitting diodes (ITOLEDs) with a microcavity structure is demonstrated. In the ITOLEDs, tris-(8-hydroxyquinoline) aluminum (Alq₃) is used as the emitting material and the outcoupling capping layer, and the 2, 9-dimethyl-4, 7-diphenyl-1, 10-phenanthroline is used as the hole/exciton-blocking layer to confine most emitting dipoles exactly at the desired resonant position. A classical optical model is adopted to simulate the electroluminescence intensity and the spectral characteristics as a function of a viewing angle. The factors that influence optical interference effects and light outcoupling are discussed systematically. The optimized ITOLED shows an enhanced outcoupling efficiency and highly saturated colors compared with that of the corresponding conventional bottom-emitting light-emitting diode while the angular dependence of the emission wavelength is minimized.