Synthesis and characterization of hole-transporting star-shaped carbazolyl truxene derivatives

Abstract

Two star-shaped carbazolyl truxene derivatives (1 and 2) are synthesized via iodination of truxene and Cu-catalyzed C–N coupling with carbazole or 3,6-di(9-carbazolyl)carbazole. In solution phase, these compounds show maximum absorption bands around 330 nm and the emission maxima at 367 and 391 nm. The emission bands shift bathochromically in solid phase as a result of the more restricted molecular vibration and rotation. Both compounds show good thermal stabilities with glass transition temperatures at 249 and 293 °C and 5% weight loss temperatures at 392 and 371 °C, respectively. Both compounds exhibit good hole-transporting properties as the devices of structure ITO/PEDOT:PSS/1 or 2/Alq₃/LiF:Al could provide maximum brightness of 12 000 cd m⁻² with turn-on voltages of 3.1–4.1 V, and maximum external quantum efficiency of 0.89–1.13%.