Synthesis of indenocarbazole-based efficient deep-blue fluorescent emitter with a narrow emission band

Deep-blue fluorescent materials are a key component in the development of organic light emitting diode (OLED). The synthesis of efficient deep-blue luminescent materials with narrowband emissions and stable OLED devices is important. Here, three new deep-blue fluorescent materials containing electron donor as an indenocarbazole and π-bridge linkage as a pyrene moiety were designed and synthesized. They possessed high thermal decomposition temperature higher than 498 °C. The three new fluorescent dopants, 1,6-DICP (1,6-bis(7,7-dimethylindeno[2,1–b] carbazol-5(7H)-yl)pyrene), 1,7-DICP (5,5′-(pyrene-1,7-diyl)bis(7,7-dimethyl-5,7-dihydroindeno [2,1–b]carbazole)), and 1,6-DIC-3,8-DIP (5,5′-(3,8-diisopropylpyrene-1,6-diyl)bis(7,7-dimethyl-5,7-dihydroindeno[2,1–b]carbazole)) were synthesized and doped in 2-methyl-9,10-bis(naphthalen-2-yl)anthracene as a blue host for emitting layer. The devices fabricated with these emitting materials showed deep-blue emission with peak wavelength (λem) at 445, 445, and 446 nm [CIE (1931): (0.15, 0.09), (0.15, 0.09), and (0.149, 0.085)]. It also exhibited high color purity with narrow spectral width (FWHM: 59 nm). In addition, they showed high external quantum efficiencies (EQE) of 3.61, 4.97, and 8.34%, respectively. In particular, the 1,6-DIC-3,8-DIP-based device exhibited high EQE and high current and power efficiencies, owing to the high photoluminescence quantum yield (PLQY) presumably due to a suppression of molecular aggregation by structural modification to give a twisted structure with a high dihedral angle.