C1‐Linked Spirobifluorene Dimers: Pure Hydrocarbon Hosts for High‐Performance Blue Phosphorescent OLEDs

: Reported here are C1-linked spiro-bifluorene dimers. A comprehensive study is carried out to analyze the electronic properties of these highly twisted structures. This work shows that the C1-position enables the design of pure hydrocarbon materials, with a high triplet energy, for hosting blue phosphors in efficient phosphorescent OLEDs (PhOLEDs). To date, this work describes the highest performance of blue PhOLEDs ever reported for pure hydrocarbons (external quantum efficiency of ca. 23 %), thus highlighting the potential of the C1-spirobifluorene scaffold in organic electronics.