High-Efficiency Bottom-Emitting Organic Light-Emitting Diodes with Double Aluminum as Electrodes

Bottom-emitting organic light-emitting diodes (BOLEDs), using Al/MoO₃ as the semitransparent anode and LiF/Al as the reflective cathode and Alq₃ as the emitter, are fabricated. At the same time, the performance improvement of the BOLEDs having a capping layer inserted between the semitransparent anode and the glass substrate is studied. The optimized microcavity BOLED shows a current efficiency (5.49 cd/A) enhancement of 10% compared with a conventional BOLED based on ITO (5.0 cd/A). Slight color variation is observed in 120° forward viewing angle with 50 nm BCP as the capping layer. Strong dependence of efficiency on Al anode thickness and the thickness and refractor index of the capping layer is explained. The results indicate that the BOLEDs with the double-aluminum electrode have potential practical applications. (paper)