Spirobifluorene derivatives for ultraviolet organic light-emitting diodes

Four new spirobifluorene (SBF) derivatives, 1,3,5-tris(9,9′-spirobifluoren-2-yl)benzene (TSBFB), 1,3-bis(9,9′-spirobifluoren-2-yl)benzene (BSBFB), 2-(1-naphthyl)-9,9′-spirobifluorene (1SBFN), and 2-(2-naphthyl)-9,9′-spirobifluorene (2SBFN), were prepared as ultraviolet (UV)-emitting materials for organic light-emitting diodes (OLEDs). These SBF derivatives all have high glass transition temperatures (Tg) above 95 °C, affording high-quality amorphous films with good morphological stability, and exhibit strong UV photoluminescence (PL) in solid state, showing no formation of excimers. In multilayer OLEDs using these SBF compounds as the emissive layers, the desired UV electroluminescence was achieved with high external quantum efficiencies of up to 2.9%. These results demonstrate that these compounds are promising UV-emitting materials for OLEDs.