P-n Metallophosphor based on cationic iridium(III) complex for solid-state light-emitting electrochemical cells

An ionic transition-metal complex for improved charge transporting properties was designed, containing both n-type dimesitylboryl (BMes ₂) and p-type carbazole groups. The complex, [Ir(Bpq) ₂(CzbpyCz)]PF₆ (1) (Bpq = 2-[4-(dimesitylboryl)phenyl] quinoline, CzbpyCz = 5,5′-bis(9-hexyl-9H-carbazol-3-yl)-2,2′- bipyridine) and its equivalent in which the BMes₂ groups were substituted with carbazole moieties were evaluated on the photoluminescence and excited state properties in detail. According to the photophysical and electrochemical properties, we concluded that the BMes₂ groups can increase the conjugation length of the cyclometalated C^N ligands and greatly enhance the phosphorescence efficiency over the carbazole groups. In addition, the bulky BMes₂ groups are effective in preventing the molecular aggregation in film. Both complexes were used to prepare single component light-emitting electrochemical cells (LECs). The electroluminescent devices show the typical behavior of LECs. The LEC based on the complex containing both electron- and hole-transporting groups shows the best performance. This work demonstrated that the design and synthesis of p-n metallophosphors will be beneficial for the improvement of device performances.