High colour rendering index white organic light-emitting devices with three emitting layers

A non-doped-type pure white organic light-emitting device with high colour rendering index has been reported. The structure of the device is ITO/m-MTDATA (45 nm)/NPB (8 nm)/DPVBi (10 nm)/DCJTB (x nm)/Alq3 (5 nm)/QAD (y nm)/Alq3 (10 nm)/BPhen (8 nm)/Alq3 (45 nm)/LiF (1 nm)/Al, where m-MTDATA is 4,4′,4″-tris{N,-(3-methylphenyl)-N-phenylamin}triphenylamine, NPB is N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1,1′-biph-enyl-4,4′-diamine, BPhen is 4,7-diphenyl-1,10-phenanthroline, Alq3 is tris-(8-hydroxyquinoline) aluminium, DCJTB is 4-(dicyanomethylene)-2-tert-butyl-6(1,1,7,7-tetramethyl julolidyl-9-enyl)-4H-pyran, QAD is quinacridone. Through the optimization of x and y, white emission with CIE coordinates of (0.33, 0.33) at 8 V was obtained, and the colour temperature and colour rendering index were 6712 K and 91 at 8 V, respectively. The Commission Internationale de 1’Eclairage (CIE) coordinates of the device change from (0.37, 0.36) at 4 V to (0.32, 0.33) at 15 V that are well in the white region. Its maximum luminance was 27360 cd/m2 at 15 V and maximum power efficiency was 3.16 lm/W at 7 V. Moreover, the current efficiency is largely insensitive to the current density.