BSB, 4,4'-di(triphenylsilyl)-biphenyl, has a structure of two triphenyllsilanes joined by a biphenyl spacer. The other family member, UGH-2, has a phenyl spacer.
Having a deep HOMO energy level and a wide bandgap, BSB is normally used as phosphorescent host for blue light-emitting materials such as FIrPic. When compared to UGH-2, it has higher glass transition temperature (Tg = 100 °C) to afford better morphology of OLED device films for higher device performance and stability. Electroluminescence devices using FIrpic as the blue phosphorescence dopant and UGH2, BSB, and BST (4,4″-bis(triphenylsilanyl)-(1,1′,4′,1″)-terphenyl) as the hosts show that BSB provides best device performance.