White organic light-emitting diodes combining vacuum deposited blue electrophosphorescent devices with red surface color conversion layers.

We report white organic light-emitting diodes (WOLEDs) combining vacuum deposited blue electrophosphorescent devices with red surface color conversion layers (CCLs). With an iridium (III) [bis(4,6-di-fluoropheny)- pyridinato-N,C(2')] picolinate (FIrpic) doped 4,4'-bis(9-carbazolyl)-2,2'-dimethyl-biphenyl (CDBP) blue electrophosphorescent light emitting layer, and an appropriate red surface CCL containing 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB), the WOLED generate high efficiency and very pure white light with a peak luminous (power) efficiency of 18.1 cd/A (9.5 lm/W) and CIE coordinates of (0.32, 0.31), very close to the equal-energy white, respectively. Moreover, the output spectra and CIE coordinates of the WOLED show no significant change at a wide range of current density.

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