A new family of bis-DCM based dopants for red OLEDs

We have synthesized a series of novel bis-DCM derivatives as candidate red dopants for use in organic light-emitting devices (OLEDs), by introducing various donor-substituted aryl rings. Compared to DCJTB (621 nm), the novel dopants (637-677 nm) showed more red-shifted emission in 1,2-dichloroethane. Using bis-DCMNEtOBu (7) as a dopant, we fabricated OLEDs with the configuration of ITO/4,49,40"-tris(3-methylphenylamino)triphenylamine (m-MTDATA) ( 20 nm)/N,N'-bis(1-naphthyl)-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) (40 nm)/tris(8-quinolinolato) aluminium (Alq(3)) : red dopant (35 nm, x wt%)/ Alq(3) (35 nm) LiF/Al. The device with a doping concentration of 1.25 wt% showed pure red emission at lambda(max) 5 654 nm ( chromaticity coordinate: x = 0.67, y = 0.33) and a maximum brightness of 2500 cd m(-2). The chromaticity coordinates were almost independent of current density. Moreover, highly efficient red emission ( x = 0.63, y = 0.36) was obtained in the 0.74 wt% doped device. The maximum external quantum efficiency was 4.46% at 7 V, the current efficiency was 3.43 cd A(-1), and the power efficiency was 1.64 lm W-1. The highest brightness of 8300 cd m(-2) was obtained at 19.6 V.