Synthesis, characterization, and application of a novel orange–red iridium(III) phosphor for solution-processed single emissive layer white organic light-emitting diodes

A novel iridium(III) complex bis(2-(naphthalen-1-yl)-6-(trifluoromethyl)benzothiazole)iridium(acetylacetonate) (CF3BT-N)2Ir(acac) with an orange–red emission was synthesized. The incorporation of CF3 and naphthalene groups into benzimidazole to act as a new ligand causes a significant change of both HOMO and LUMO energy levels of the iridium complex compared with the yellow emissive parent compound comprising the 2-phenylbenzimidazole ligand. As a result, a bathochromic shift by as much as 50 nm of the phosphorescence emission peak can be achieved. Electronic properties of (CF3BT-N)2Ir(acac) were examined by time-dependent density functional theory (TD-DFT) calculations. The influence of such substituent groups on the photophysical, electrochemical and electroluminescent properties of iridium complex was studied. Furthermore, two- and three-element solution-processed white organic light-emitting diodes (WOLEDs) with high performance can be realized by using this kind of orange–red phosphorescent emitter in conjunction with other phosphors in a single emissive layer. A maximum luminous efficiency of 10.9 cd A−1 with CIE coordinates of (0.27, 0.37) was obtained for the two-element WOLEDs. For the three-element WOLED, a maximum luminance of 22716 cd m−1 and a maximum luminous efficiency of 14.6 cd A−1 with CIE coordinates of (0.33, 0.42) can be achieved.