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,C2′) 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 ηext,tot=13.1±0.5% and ηp,tot=20.2±0.7lm∕W, respectively, at a luminance of 800cd∕m2 with Commission Internationale de L’Eclairage chromaticity coordinates of (x=0.38, y=0.42) and a color rendering index of 79.