Tetraphenylsilane group containing carbazoles as high triplet energy host materials for solution-processable PhOLEDs

Abstract

A series of solution processable, wide band-gap host materials composed of carbazole and tetraphenylsilane groups were designed and synthesized. Their thermal, electrochemical, and photophysical properties were fully investi- gated. The introduction of bulky tetraphenylsilane and tert-butyl groups around the carbazole led to high glass transition temperatures (Tg) between 120 and 204 ° C. The triplet energies (ET ) of the synthesized materials were examined by low temperature (77 K) photoluminescence studies and determined as ET > 2.6 for all compounds. Phosphorescent organic light-emitting devices with the ITO/PEDOT:PSS/EML/TPBi/Cs2CO3 /Al device structure were fabricated by using synthesized materials as the host and two kinds of phosphorescent emitters, FIrpic and Ir(ppy)3 , as the guests. The highest luminous and power efficiency values obtained by using FIrpic were 3.6 cd A -1 and 1.48 lm W -1 , respectively, with commission International de I'Eclairage (CIE) coordinates of (0.17, 0.36), whereas these values were 7.8 cd A -1 and 2.9 lm W -1 for the device structure when Ir(ppy)3 was used as the guest [CIE (0.28, 0.62)].