Blue electroluminescence from spiro-configured polyfluorene derivatives with hetero-atoms

New polyfluorene (PF) derivatives with hetero-atom containing spiro-rings were characterized. The polymers showed typical optical properties of PFs with pure blue emission and enhanced thermal properties due to the presence of bulky spiro-rings at C-9 position of the fluorene unit. Hetero-atoms, even when in spiro-rings, affected the energy levels of the polymers. In particular, the nitrogen-containing polymer showed an improved HOMO level for efficient hole injection at 5.35 eV and a polymer light-emitting diode (PLED) based on the polymer showed low turn-on and operating voltages.