A novel tetraphenylsilane-phenanthroimidazole hybrid host material for highly efficient blue fluorescent, green and red phosphorescent OLEDs

A novel organosilane compound, bis(4-(1-phenylphenanthro[9,10-d]imidazol-2-yl)phenyl) diphenylsilane (Si(PPI)(2)), has been designed and synthesized. It has a high thermal decomposition temperature of 528 degrees C and is able to form an amorphous glass with a high glass-transition temperature of 178 degrees C. In addition, it possesses high singlet and triplet energies and displays efficient energy transfer to the selected blue fluorescent and green and red phosphorescent dopants when used as a host material. Electrochemical measurements and single-carrier devices indicate that Si(PPI)(2) is a bipolar transport material, allowing the injection and transport of both electrons and holes. By using (Si(PPI)(2)) as a host, high-performance fluorescent blue (FB) and phosphorescent green (PG) and red (PR) OLEDs with a uniform and simple device configuration have been achieved. These OLEDs exhibit very high peak external quantum efficiency (EQE) and peak power efficiency (PE), i.e. 6.1% and 8.0 lm W-1 for FB, 19.2% and 51.1 lm W-1 for PG and 12.0% and 15.6 lm W-1 for PR. Moreover, the high-level EQE of 4.0, 19.1 and 10.6% and PE of 3.0, 41.6 and 7.5 lm W-1 can be maintained by FB, PG and PR, respectively, at the practical luminance of 100 cd m(-2). Furthermore, the emission colors of these OLEDs remain almost unchanged within the whole range of driving voltages. Importantly, the blue OLED displays a pure blue emission (CIE: 0.18, 0.17).