Controllably Tuning Excited‐State Energy in Ternary Hosts for Ultralow‐Voltage‐Driven Blue Electrophosphorescence

A series of dibenzofuran-based ternary hosts were designed and prepared. The singlet energy levels and carrier injecting/transporting abilities were adjusted on the basis of the mixed meso and short-axis linkages (see picture). By harmonizing the optical and electrical properties, the blue-emitting diodes realized highly efficient blue electrophosphorescence with ultralow driving voltages.