Deep-blue and white organic light-emitting diodes based on novel fluorene-cored derivatives with naphthylanthracene endcaps

Novel fluorene based deep-blue-emitting molecules with naphthylanthracene endcaps, namely 2,7-di (10-naphthylanthracene-9-yl)-9,9-dioctylfluorene (NAF1) and 7,7'-di(10-naphthylanthracene-9-yl)-9,9,9',9'-tetraoctyl-2,2'-bifluorene (NAF2), are synthesized by a Suzuki cross-coupling reaction. These materials exhibit excellent thermal and amorphous stabilities, and high fluorescence quantum yield of over 70%. Organic light-emitting devices (OLEDs) using NAF1 or NAF2 as non-doped emitter exhibit bright deep blue electroluminescence with CIE coordinates of (0.15, 0.13) for NAF1, (0.16, 0.13) for NAF2. A maximum power efficiency of 2.2 lm W-1 (4.04 cd A(-1), 4.04%) is achieved for NAF1, which is among the highest values ever reported for deep-blue fluorescent OLEDs. A further improved coordinates of (0.15, 0.09) with efficiencies of 3.56 cd A(-1) and 2.10 lm W-1 are achieved for NAF1 upon tuning device thickness, which are also among the best data for non-doped deep blue fluorescent OLEDs with a CIE coordinate of y < 0.1. NAF1 serves as excellent host emitter when doped with an orange fluorophore (4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran, DCJTB). Upon careful tuning the doping level, the two-emitting- component (NAF1 : DCJTB) OLED realizes efficient white light emission with a power efficiency of 3.01 lm W-1 (7.66 cd A(-1)), a brightness of 12090 cd m(-2), and a standard white light coordinates of (0.33, 0.33). This performance is among the best results ever reported for two-emitting- component white OLEDs based on fluorescent materials.