Green iridium complexes based on pyrimidine derivatives for efficient electroluminescence with EQE near 30%

To obtain dopants owing excellent electron mobility, four novel iridium (III) complexes (Ir(tfmppm)2(acac), Ir(tfmppm)2(tpip), Ir(f-4-tfmppm)2(tpip) and Ir(f-3-tfmppm)2(tpip)) with green emission using 2-(2,6-bis(trifluoromethyl)pyridin-4-yl)pyrimidine (tfmppm), 2-(2,6-bis(trifluoromethyl)pyridin-4-yl)-5-fluoropyrimidine (f-4-tfmppm) and 2-(2,6-bis(trifluoromethyl)pyridin-3-yl)-5-fluoropyrimidine (f-3-tfmppm) as main ligands, acetylacetonate (acac) and tetraphenylimidodiphosphinate (tpip) as ancillary ligands, were investigated, respectively. Due to the variation of the structures among the complexes, the photoluminescence quantum yield (up to 94%) and electron mobility can be regulated gradually, which would broaden the recombination zone, balance the distribution of holes and electrons, leading to excellent electroluminescence (EL) performances. Among four emitters, the organic light-emitting diodes (OLEDs) using Ir(f-3-tfmppm)2(tpip) display the best EL performances with a maximum current efficiency of 92.83 cd A−1 and a maximum external quantum efficiency of 29.5%, suggesting these materials have potential application in OLEDs.