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

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 investigated. The introduction of bulky tetraphenylsilane and tert-butyl groups around the carbazole led to high glass transition temperatures (T-g) between 120 and 204 degrees C. The triplet energies (E-T) of the synthesized materials were examined by low temperature (77 K) photoluminescence studies and determined as E-T > 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)].