White and red organic light-emitting diodes using a phosphorescent iridium complex as a red dopant

In this paper, we describe the phosphorescent characteristics of a red-emitting iridium complex, bis(2-naphthalen-1-yl-5-trifluoromethyl-pyridine- N, C2) iridium(III) acetylacetonate [(5-fnapy)2 Ir (acac)], together with investigating the electroluminescence (EL) mechanisms of organic light-emitting diodes (OLEDs) by using this complex as a red dopant. A bright white and red light emission can be realized using the indium tin oxide/ α -naphthylphenylbiphenyl (NPB)/ 4, 4′ -N, N′ -dicarbazole-biphenyl (CBP) (5-fnapy)2 Ir (acac) BAl q3 LiFAl structure with different concentrations of (5-fnapy)2 Ir (acac) in CBP host. With the dopant concentration above 9%, the red emission with Commission Internationale De L'Eclairage (CIE) coordinates x=0.65, y=0.34, maximum luminance of 7240 cd m2 and luminous efficiency of 7.1 cdA was obtained in the device. The white-emitting device with a maximum luminance of 3060 cd m2 and maximum luminous efficiency of 4.0 cdA was obtained via doping 1.5% (5-fnapy)2 Ir (acac). The white-emission spectrum of this device is composed of a red band from (5-fnapy)2 Ir (acac) and two blue emissions from NPB and BAl q3. The CIE coordinates were well within the white zone, which moves slightly from (0.33, 0.32) to (0.36, 0.33) when applied voltage is varied from 9 to 18 V. The Electrochemical Society