Novel tetraarylsilane-based hosts for blue phosphorescent organic light-emitting diodes

Two highly twisted tetraarylsilane derivatives containing carbazole and benzimidazole were designed and synthesized with high triplet energy level (E-T) as hosts for blue phosphorescent organic light-emitting diodes (PHOLEDs). The thermal, photophysical, electrochemical properties and geometry optimization of materials were studied. The central silicon atom effectively disconnected the electronic interactions among the three functional units in a molecule, resulting in high E-T and relatively wide band gap (E-g) (>= 3.5 eV). Finally, the blue PHOLED devices using 3,3'-((phenyl(4-(9-phenyl-9H-carbazol-2-yl)phenyl)silanediyl)bis(4,1-phenylene)) bis(9-phenyl-9H-carbazole) (TCzSi) as host material achieved a maximum current efficiency of 25.5 cd A(-1), a maximum power efficiency of 18.15 lm W-1, a maximum luminance of 6285 cd m(-2) and a maximum external quantum efficiency (EQE) of 13.32%. This study showed a molecular design strategy to develop novel tetra-arylsilane-based compounds for blue hosts.