High-Performance All-Aryl Phenazasilines via Metal-Free Radical-Mediated CH Silylation for Organic Light-Emitting Diodes

Heteroatom-containing organic molecules show a unique combination of properties for high-performance optoelectronic applications. With both Si and N heteroatoms in an aromatic architecture, phenazasilines are promising for optoelectronic devices, except for their synthetic difficulties. Through a newly developed two-step SiH/CH coupling silylation in a metal-free intramolecular radical-mediated catalysis mechanism, all-aryl phenazasilines that can be hardly synthesized by previous methods are facilely prepared and found to have excellent optoelectronic properties with both high thermal stability and high solubility due to the effects of bulky diphenyl substituents on Si, which cannot only strengthen the intramolecular interactions but also alleviate the intermolecular packing of phenazasilines. Using these compounds as host materials, high device performance was achieved with external quantum efficiency up to 21.3% and very low efficiency roll-off (1.4% at 1000 cd m⁻²), which are among the best of the recent reported results of blue phosphorescent organic light emitting diodes. This design strategy featuring rigid all-aryl phenazasiline motifs and the metal-free radical-catalyzed synthetic methodology should be important in developing high-performance multiheteroatom modified aromatic molecules for organic optoelectronics.