Highly efficient pyrene blue emitters for OLEDs based on substitution position effect

To investigate the effect of substitution position of the side group on a pyrene core, three derivatives having a triphenylbenzene group as a bulky side group at the 1,6-position, 4,9-position, and 1,8-position were successfully synthesized: 1,6-bis(5′-phenyl-[1,1':3′,1″-terphenyl]-4-yl)pyrene (1,6-DTBP), 4,9-bis(5′-phenyl-[1,1':3′,1″-terphenyl]-4-yl)pyrene (4,9-DTBP), and 1,8-bis(5′-phenyl-[1,1':3′,1″-terphenyl]-4-yl)pyrene (1,8-DTBP). The three synthesized materials showed excellent thermal stability with a high Tg of >140 °C and a high Td of >500 °C. Due to the highly twisted structure of 1,8-DTBP in the film state, the absolute photoluminescence quantum yield value was improved. Of the three synthesized materials used as an emitter in a non-doped organic light-emitting diode device, 1,8-DTBP showed highly efficient electroluminescence performance, with a luminance efficiency of 6.89 cd/A, power efficiency of 3.03 lm/W, and external quantum efficiency of 7.10% at 10 mA/cm2. In addition, 4,9-DTBP showed a deep-blue emission of CIE x, y (0.158, 0.063) suitable for HD-TV.