Top-emitting white organic light-emitting diodes with a color conversion cap layer

We report top-emitting white organic light-emitting diodes (WOLEDs) by thermally evaporating non-doped (4-(4-(1,2,2-triphenylvinyl)phenyl)-7-(5-(4-(1,2,2-triphenylvinyl)phenyl)thiophen-2yl)benzo[c][1,2,5]thiadiazole) (BTPETTD) as a color conversion cap layer on top-emitting blue OLEDs. With a 240 nm cap layer, 74.5% of the blue photon energy are absorbed and converted to red emission with a conversion efficiency of 40%. By mixing the unabsorbed blue emission and red emission, the resulting top-emitting WOLEDs exhibit a broad band spectra with CIE coordinates of (0.34, 0.35), high color stability over a wide range of driving voltages, and peak efficiency of 17.7 cd/A and 8.7 lm/W. (C) 2011 Elsevier B.V. All rights reserved.