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 (BMes2) 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.