Synthesis of carbazole/triarylamine containing polyfluorene and its application to electroluminescent devices

Solution-processable carbazole/triarylamine-based polyfluorene (CT-PF) was designed and synthesized by Suzuki coupling reaction. CT-PF was originally designed to have multiple functions at the same polymer backbone; blue emission and large band gap energy by fluorine group as well as good hole transporting property and tunable ionization potential by excellent electron donating triarylamine and carbazole moieties. It was confirmed from TGA measurement that the synthesized CT-PF had thermal stability up to 379 degrees C. The UV-Visible absorption spectra of CT-PF had absorption maxima at 292 nm and 351 nm in dilute solution, and 332 nm and 400 nm in film state, which might be originated from fluorene and arylamine moieties. PL emission maxima were also measured in the blue range at 425 nm in dilute solution and 468 nm in film state. Turn-on voltage of double-layered OLED with CT-PF as HTL was reduced to 7 V, and the luminescence were enhanced up to 1,397 cd/m2 with maximum current efficiency of 0.32 lm/W and power efficiency of 1.1 cd/A, which were over 3 times higher than those of single-layered device without HTL. PhOLED with CT-PF as a host material for Ir(ppy)3 phosphorescent dopant showed bright green emission with CIE color coordinates as (x = 0.31, y = 0.57).