Uniform dispersion of triplet emitters in multi-layer solution-processed organic light-emitting diodes

The influence of the iridium complex solubility on the efficiency of multi-layer solution-processed organic light-emitting diode is demonstrated by synthesized orange triplet iridium complexes with the same core. The solubility of the iridium(III) bis(4-phenylthieno[3,2-c]pyridinato-N,C2′) acetylacetonate is increased and uniform dispersion of iridium complex in polymer host poly(vinylcarbazole) is achieved by tert-butyl and n-hexyl group modification. Blade coating technique is utilized to achieve tri-layer structures with a polymer hole-transporting layer poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(4-s-butylphenyl))diphenylamine)], a host–guest emissive layer, and small-molecule hole-blocking layer 1,3,5-tris(N-phenylbenzimidazol-2-yl) benzene. The efficiency as high as 20 cd/A is achieved for orange-emitting device.