Highly Efficient Orange and Warm White Phosphorescent OLEDs Based on a Host Material with a Carbazole-Fluorenyl Hybrid

Abstract

A new carbazole–fluorenyl hybrid compound, 3,3′(2,7-di(naphthaline-2-yl)-9H-fluorene-9,9-diyl)bis(9-phenyl-9H-carbazole) (NFBC) was synthesized and characterized. The compound exhibits blue-violet emission both in solution and in film, with peaks centered at 404 and 420 nm. In addition to the application as a blue emitter, NFBC is demonstrated to be a good host for phosphorescent dopants. By doping Ir(2-phq)3 in NFBC, a highly efficient orange organic light-emitting diode (OLED) with a maximum efficiency of 32 cd A−1 (26.5 Lm W−1) was obtained. Unlike most phosphorescent OLEDs, the device prepared in our study shows little efficiency roll-off at high brightness and maintains current efficiencies of 31.9 and 26.8 cd A−1 at a luminance of 1000 and 10 000 cd m−2, respectively. By using NFBC simultaneously as a blue fluorescence emitter and as a host for a phosphorescent dopant, a warm white OLED with a maximum efficiency of 22.9 Lm W−1 (21.9 cd A−1) was also obtained.