NIR-OLED structures based on lanthanide coordination compounds: synthesis and luminescent properties

Abstract

Electroluminescence complexes based on ytterbium and 5-methyl-2-phenyl-4-(2,2,2-trifluoroacetyl)-2,4-dihydro-3H-pyrazol-3-one (HL) ligand and various diimine-type ancillary ligands (2,2-bipyridine, bathophenanthroline, 1,10-phenanthroline) have been synthesized, and corresponding crystals were investigated. [Yb(L)₃(bipy)] and [Yb(L)₃(bath)] complexes have triclinic structure (P-1), while [Yb(L)₃(phen)] complex has orthorhombic structure (P2₁2₁2₁). The crystallography parameters were determined. The photoluminescence of the complexes demonstrated only bands resulted from ${}^2{F}_{5/2}^{}{\to }^2{F}_{7/2}^{}$ transition and corresponding three Stark subcomponents generated due to the crystal field action. NIR-OLED structures with emitting layers based on the [Yb(L)₃(bipy)], [Yb(L)₃(bath)], and [Yb(L)₃(phen)] complexes have been fabricated, and their electroluminescence demonstrated maxima intensities at 978 and 1005 nm. Comparison of NIR-OLEDs power density showed that the maximal power densities of 2.17 (978 nm) and 1.92 (1005 nm) μW × cm⁻² were determined for the NIR-OLED based on [Yb(L)₃(bath)] complex.