Codoped Spacer Ratio Effect on Electroluminescence Characteristics of Hybrid White Organic Light-Emitting Diodes for Reduced Efficiency Roll-Off

Abstract

We demonstrated hybrid white organic light-emitting diodes (HWOLEDs) using 1,4-bis{2-[7-N-diphenyamino-2-(9,9-diethyl-9H-fluoren-2-yl)]vinyl} benzene as the fluorescent blue emitter and iridium(III) bis(2-phenylquinoline) acetylacetonate as the phosphorescent red emitter. We also investigated the codoped spacer ratio (CSR) effects of 4,4',4 ''-tris(N-carbazolyl)-triphenylamine(TCTA)and2,2',2 ''-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBI) on the electroluminescence characteristics of HWOLEDs. The optimized HWOLED with a CSR of 1 : 3 (TCTA: TPBI) exhibited a lower efficiency roll-off of 32% than the control device (67%) with a CSR of 1 : 1 (TCTA: TPBI). The HWOLED also showed a current efficiency of 12.76 cd/A, an external quantum efficiency of 6.95%, and Commission Internationale de l'Eclairage coordinates of (0.38, 0.39) at 1000cd/m(2). (C) 2010 The Japan Society of Applied Physics