Electrophosphorescence from hole-transporting layer doped with cerium halide nano-particles

Hybrid films of hole-transporting compounds embedded with cerium halides nano-particles were successfully prepared by simultaneous vacuum deposition of hole-transporting compounds and cerium halides. From observation by transmission electron microscopy, it was confirmed that cerium halides formed spherical nano-particles with diameter of less than 20 nm. The hybrid films exhibited fluorescence by irradiation of ultraviolet light. However, fairly efficient electrophosphorescence was confirmed in the electroluminescence device having the hybrid films as an emissive layer. When the hybrid film of 4,4′-N,N′-dicarbazole-biphenyl doped with cerium iodide nano-particles was used, maximum luminance was 486 cd cm−2, and maximum external quantum efficiency was 0.11%.