Top emission organic light emitting diode with a Cr/Al/Cr anode

A top emission organic light emitting diode (TEOLED) comprised of a Cr anode on PES film/NPB/Alq3/cathodes has been fabricated. The triple layer structure of Cr/Al/Cr allowed for fabrication of a crack-free anode and provided better thermal stability and higher work function than a conventional ITO anode. For the Cr/Al/Cr anodes, a series of Cr layers with various surface morphology has been tested. A Cr layer with a smooth surface morphology was found to be optimal. The TEOLED fabricated on PES film having good anode surface morphology showed similar device characteristics to that on a Si wafer. TEOLEDs on PES film and Si wafer exhibited a maximum luminous efficiency of 2.87 and 3.0 cd/A, respectively, at 1000 cd/m2 with a NPB/Alq3/LiF/Al/Ag structure on a Cr/Al/Cr anode.