High-efficiency microcavity top-emitting organic light-emitting diodes using silver anode

Top-emitting organic light-emitting diodes (TOLEDs) employing highly reflective Ag as anode and semitransparent LiF/Al/Ag as cathode were fabricated. The hole injection efficiency of Ag anode can be significantly improved with surface modification using a CF4 plasma. With C545T-doped Alq(3) emitter, the top-emitting device shows a low turn-on voltage of 2.65 V. The optimized microcavity TOLED shows a current efficiency enhancement of 65% and a total outcoupling efficiency enhancement of 35%, compared with a conventional OLED. No color variation was observed in the forward 140 degrees forward viewing cone. Strong dependence of efficiency on Ag cathode thickness was observed, in good agreement with numerical simulations. (c) 2006 American Institute of Physics.