Two new mixed ligand complexes [Eu(tfac)3(DPEPO)] (Eu-1) and [Tb(tfac)3(DPEPO)] (Tb-2) incorporating trifluoroacetylacetone (Htfac) and bis(2-(diphenylphosphino)phenyl)ether oxide (DPEPO) were synthesized in gram-scale quantities and used as emitters to fabricate single- and double-EML (light-emitting layer) electroluminescence (EL) devices. The single-EML device with the structure: ITO/HAT-CN (6 nm)/HAT-CN (0.2 wt%):TAPC (50 nm)/Eu-1 (1-6 wt%): 26DCzPPy (10 nm)/Tm3PyP26PyB (50 nm)/LiF (1 nm)/Al (100 nm) showed light red (CIE, x: 0.574; y: 0.275) emission for the Eu-1 based EL devices due to the presence of a host emission with a brightness of 1274 cd m-2, current efficiency (ηc), power efficiency (ηp) and external quantum efficiency (EQE) of 0.58 cd A-1, 0.68 lm W-1, and 0.70%, respectively. The single-EML device for the Tb-2 complex with the same device structure displayed white-light emission. The optimized single-EML device of Tb-2 with 14.0 wt% doping concentration showed an impressive EL performance with brightness of 1637 cd m-2, ηc ≈ 3.05 cd A-1, ηp ≈ 2.80 lm W-1, EQE ≈ 1.4%, Vturn-on ≈ 3.1 V, respectively. This is the first report of single component white organic light emitting diode (W-OLED) fabricated from an organo-Tb(iii) complex. The W-OLEDs show low turn-on voltages (Vturn-on) ≈ 3.1 V and are thus advantageous in lowering the power consumption of the OLED display.
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