Photoluminescence and electroluminescence properties of three ternary lutetium complexes

Abstract

Three lutetium complexes, Lu(PMIP)₃(TPPO)₂ (A), Lu(PMIP)₃Bipy (B) and Lu(PMIP)₃Phen (C) (where PMIP, TPPO, Bipy and Phen stand for 1-phenyl-3-methyl-4-isobutyryl-5-pyrazolone, triphenylphosphinoxide, 2,2′-bipyridine and 1,10-phenanthroline, respectively), were synthesized and complex A was characterized by single-crystal X-ray diffraction analysis. Complex A was found to crystallize in the P2₁/n (14) space group. The photoluminescence spectra of the complexes reveal that all the complexes have a similar spectrum peaking near 440 nm; however, the intensity of the spectrum of complex A is about 100 times higher than that of the other two complexes. When these complexes were utilized to prepare light-emitting devices, that with complex A gave a blue light, originating from this complex, with the highest brightness of 119 cd m⁻² at an applied voltage of 19 V, while the same configuration devices using the other two complexes exhibited green light peaking at 512 nm, which arises from exciplexes formed at the interface of TPD and the corresponding lutetium complex. A maximum luminance of 1010 cd m⁻² at 16 V from the exciplex was obtained with the highest power efficiency of 0.13 lm W⁻¹ at 9 V and a turn-on voltage as low as 3 V for the device with a (ITO)/TPD(10 nm)/B(50 nm)/BCP(20 nm)/AlQ(40 nm)/Mg_0.9Ag_0.1(100 nm)/Ag (100 nm) configuration.