This paper describes a red dopant material, the cyanocoumarin derivative 9-cyano-10-͑2-benzothiazolyl͒-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-benzo ͓l͔ pyrano͓6,7,8-i j͔quinolizin-11-one ͑RC545T͒, and its use in organic light-emitting diodes ͑OLEDs͒. Because RC545T exhibits ͑i͒ redshifted fluorescence ͑ max = 607 nm͒ and ͑ii͒ a narrower full width at half-maximum ͑fwhm; 48 nm͒ relative to the corresponding signal for 4-͑dicyanomethylene͒-2-tert-butyl-6-͑1,1,7,7-tetramethyljulolidyl-9-enyl͒-4H-pyran ͑DCJTB; max = 605 nm; fwhm = 73 nm͒, which is currently one of the most efficient red dopant materials, we could fabricate red OLEDs exhibiting improved color purity. A device incorporating RC545T as a dopant and rubrene as an assistant dopant in the configuration indium-tin oxide ͑ITO͒/N,NЈ-bis͑1-naphthyl͒-N,NЈ-diphenyl-1,1Ј-biphenyl-4,4Ј-diamine ͑65 nm͒/tris͑8-hydroxyquinoline͒aluminum ͑Alq 3 ͒:15 wt % rubrene:2 wt % RC545T ͑30 nm͒/Alq 3 ͑30 nm͒/LiF ͑0.8 nm͒/Al ͑250 nm͒ exhibited a maximum luminance of 8000 cd/m 2 at 12.5 V, with near-saturated CIE coordinates of ͑0.64, 0.35͒, significantly better red color purity than that of the device featuring DCJTB as the dopant material ͓CIE coordinates: ͑0.63, 0.37͔͒, thereby rendering RC545T a good red-emitting dopant for OLED applications.
