Coordination complexes exhibiting room-temperature phosphorescence: Evaluation of their suitability as triplet emitters in organic light emitting diodes

The aim of this review is to evaluate the potential of known main-group, transition metal and lanthanide complexes exhibiting room-temperature phosphorescence, either for direct application as dopants in the emissive layer of OLED devices, or as an aid to deduce which structural trends might lead to new materials for this purpose. A systematic analysis of emission characteristics such as wavelength, quantum yields and lifetimes is given for known classes of complexes and their suitability as OLED phosphors evaluated. Blue electroluminescent devices remain to date the most challenging area of this technology, and polynuclear copper(I), mono-, di- and polynuclear gold(I) and osmium(II) complexes are identified as being of particular promise in this regard. Heterobimetallic complexes are also identified as being of interest because of the possibility for emission tuning, by suitable choice of metals and ligands, which these complexes may offer.