Enhancement in brightness and efficiency of organic electroluminescent device using novel N,N-di(9-ethylcarbaz-3-yl)-3-methylaniline as hole injecting and transporting material

Abstract

A novel hole injecting and transporting material, N,N-di(9-ethylcarbaz-3- yl)-3-methylaniline (DECMA), was prepared by one-step reaction for use in organic electroluminescent (EL) devices. Organic EL device with configuration of ITO/DECMA (60nm)/NPB (10nm)/Alq3 (60 nm)/Mg:Ag/Ag turned on at 3.7 V and displayed a brightness of 1150 cd m-2 and a current efficiency of 5.5 cd A-1 at the current density of 20 mA cm-2, while a reference device with configuration of ITO/NPB (70 nm)/Alq3 (60 nm)/Mg:Ag/Ag turned on at 3.9 V and exhibited a brightness of 500 cd m -2 and a current efficiency of 2.4 cd A-1 at the same current density. The lower turn on voltage and higher brightness and efficiency obtained in DECMA-containing device can be ascribed to the improved hole injection at anode/organic interface due to the low ionization potential of DECMA and the better balanced hole-electron recombination in emitting layer due to the moderate hole drift mobility of DECMA. © 2004 Elsevier B.V. All rights reserved.