Improvement of color purity in white OLED based on Zn(HPB)2 as blue emitting layer

We synthesized zinc (II) [2-(2-hydroxyphenyl)benzoxazole] (Zn(HPB)(2)) as blue emitting materials and evaluated in the organic light emitting diodes (OLEDs). The layer of Zn(HPB)2 doped with 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) (Zn(HPB)2:DCJTB) as emitters has been demonstrated. The structure of the device is indium-tin-oxide (ITO)/N,N'-bis-(1-naphthl)-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB, 40 nm)/Zn(HPB)(2)/Zn(HPB)(2):DCJTB/Alq(3) (20 nm)/LiF/Al. The thickness of Zn(HPB)(2) layer was 0, 10, 20, 30 nm at the same time the thickness of Zn(HPB)(2):DCJTB layer were 40, 30, 20, 10 nm. When thickness of Zn(HPB)(2) layer was 30 nm and the thickness of Zn(HPB)2:DCJTB layer was 10 nm, white emission is achieved. The Commission Internationale de l'Eclairage (CIE) coordinates of the white emission are (0.304, 0.332) at an applied voltage of 10.5V. (c) 2007 Elsevier B.V. All rights reserved.