Solution-Processed Double-Silicon-Bridged Oxadiazole/Arylamine Hosts for High-Efficiency Blue Electrophosphorescence

A series of oxadiazole/arylamine hybrids, namely p OXDDSiPA, p OXDDSiCz, m OXDDSiPA, and m OXDDSiCz, were designed and synthesized by incorporating electron-donating diphenylamine or 3,6-di- tert -butyl-9 H -carbazole unit and electron-accepting oxadiazole moiety into one molecule via double-silicon-bridged linkage. This design strategy of extending molecular structure endows these compounds with good solution processability, and high thermal and morphological stability, without lowering their triplet energies. These compounds exhibit similar energy levels and higher glass transition temperatures (92–190 °C) relative to the corresponding single-silicon-bridged congeners. The reasonable combination of the tetra- meta -position linking topology and electron donor diphenylamine group imparts the compound m OXDDSiPA with both relative high triplet energy (2.72 eV) and high-lying HOMO level (5.30 eV). As a result, the best EL performance was achieved for the m OXDDSiPA-based blue phosphorescent device, with a maximum current efficiency of 23.4 cd A –1, a maximum power efficiency of 10.2 lm W –1, and a maximum external quantum efficiency of 10.7%. Moreover, the current efficiency remains as high as 23.3 cd A –1 at the luminance of 100 cd m –2, and even at the high luminance of 1000 cd m –2, the efficiency is still 17.7 cd A –1 .