A series of 1-phenylisoquinoline derivatives encapsulated with peripheral arylamines as dendrons are synthesized by using the Ullmann reaction and palladium-catalyzed aromatic carbon–carbon Suzuki-coupling reactions. Red-emitting dendritic iridium complexes (called G1-1, G1-2, and G2) are synthesized using the following derivatives: N,N-diphenyl-3′-isoquinolin-4-biphenylaniline, N,N-di(9,9-dimethylfluorenyl-3′-isoquinolin-4-biphenylaniline, N,N-di(4′-di(2′-(9′,9′-dimethylfluorenyl)amine)biphenyl-3′-isoquinolin-4-biphenylaniline as the first ligands and 5-methyl-3-(pyridin-2′-yl)-1H-1,2,4-triazole as an ancillary ligand. The obtained dendrimers are soluble in common organic solvents, and uniform thin films can be spin-coated from such solutions. Devices fabricated from dendritic iridium complexes G1-2 and G2 with a small molecule host are fabricated by spin-coating from chloroform solution in different device configurations. G1-2 and G2 show similar device performances with maximum external quantum efficiencies (EQEs) of 12.8 % and 11.8 % (photons/electron) and luminous efficiency of 9.2 cd A–1 and 8.5 cd A–1 at 0.1 mA cm–2, respectively. Devices based on polymer host poly(9,9-dioctylfluorene)(PFO) (30 % PBD (2-(4-biphenyl)-5-(4-tert-butylphenyl-1,3,4-oxadiazole)) show a slightly higher efficiency for G1-2, with a maximum EQE of 13.9 % at a much higher current density of 6.4 mA cm–2 and luminance of 601 cd m–2.