Energy transfer and morphology study of a new iridium based cyclometalated phosphorescent complex

This paper reports synthesis and characterization of a new phosphorescent iridium complex namely iridium (III) bis (2-phenylpyridinato–N, C2′) picolinate [(ppy)2Irpic]. For its future use in organic light emitting diodes (OLED), we doped the iridium complex into various host materials and carried out a study of energy transfer process through photoluminescence (PL) and photoluminescence excitation (PLE) measurements onto the blended films with different concentrations of (ppy)2Irpic. The blended films were casted by the spin coating method, as to make the device fabrication process cheaper. The selected host materials were poly(N-vinylcarbazole) (PVK), poly(9,9-dihexylfluorene) (PDHF) and N,N′-diphenyl-bis(3-methylphenyl) [1,1′-biphenyl]-4,4′-diamine (TPD). The blended films with TPD as a host were made in poly(methyl-methacrylate) (PMMA) matrix. The emission from the host molecule disappears at a particular concentration of (ppy)2Irpic, which is determined as 5 wt%, 12 wt% and 20 wt% of the host materials for blended PVK, TPD (20% by weight of PMMA) and TPD (10% by weight of PMMA) films, respectively. No energy transfer could be observed for PDHF for the concentration range of 0.1–20 wt%. The energy transfer efficiency and the morphology of the various blends were also studied in order to find out the most appropriate host material for the device applications.