White organic light-emitting device based on a compound fluorescent-phosphor-sensitized-fluorescent emission layer

The authors demonstrate a combination fluorescent and phosphor-sensitized-fluorescent white organic light-emitting device (WOLED), employing the conductive host material, 4,4(')-bis(9-ethyl-3-carbazovinylene)-1,1(')-biphenyl, doped with the phosphorescent green, and the fluorescent red and blue emitters, fac-tris(2-phenylpyridinato-N,C-2') iridium (III), 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran, and 4,4(')-bis (9-ethy-3-carbazolvinylene)-1-1(')-biphenyl, respectively. Although two fluorescent dopants are employed along with only a single phosphor, this simple structure can, in principle, achieve 100% internal quantum efficiency. In the prototype, the phosphor-sensitized WOLED exhibits total external quantum and power efficiencies of eta(ext,tot)=13.1 +/- 0.5% and eta(p,tot)=20.2 +/- 0.7 lm/W, respectively, at a luminance of 800 cd/m(2) with Commission Internationale de L'Eclairage chromaticity coordinates of (x=0.38, y=0.42) and a color rendering index of 79. (c) 2006 American Institute of Physics.