Highly efficient simplified organic light emitting diodes

The authors report on highly efficient organic light emitting diodes (OLEDs) consisting of only two organic layers. The key to the simplification is the direct injection of holes into the wide band gap hole transport material 4,4('),4(')-tris(N-carbazolyl)-triphenyl amine (highest occupied molecular orbital is 5.9 eV) through an indium tin oxide/tungsten oxide (WO3) anode. Kelvin probe analysis has revealed an extremely high work function of 6.4 eV for WO3. The efficiencies of the simplified OLEDs exceed 40 lm/W and 45 cd/A at a brightness of 100 cd/m(2), unsurpassed by other comparably simple OLED devices. Therefore, our OLED architecture demonstrates highly efficient, yet easy to fabricate devices.