Efficient Visible-Light-Excitable Eu3+ Complexes for Red Organic Light-Emitting Diodes

authors	Francis, B; Nolasco, MM; Brandao, P; Ferreira, RAS; Carvalho, RS; Cremona, M; Carlos, LD
nationality	International
journal	EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
author keywords	Luminescence; Europium; Photophysics; Visible-light excitation; LUMPAC; OLEDs
keywords	BETA-DIKETONATE COMPLEXES; LUMINESCENT LANTHANIDE COMPLEXES; INTRAMOLECULAR ENERGY-TRANSFER; EMISSION QUANTUM YIELD; RADIATIVE LIFETIME; INORGANIC HYBRIDS; LIGAND; EUROPIUM(III); SENSITIZATION; OXIDE
abstract	Visible-light-excited Eu3+ complexes have received much attention in the last years due to the rapidly increasing demand for less-harmful biomarkers and low-voltage driven emitters in optoelectronics. Nevertheless, these complexes usually exhibit poor emission quantum yields, contrarily to the ones excited in the ultraviolet spectral region. To address this challenge, a series of complexes based on trivalent lanthanide ions, [Eu(bpyO2)(CH3OH)(2)(H2O)(NO3)(2)](NO3) (1), [Gd(bpyO2)(H2O)(4)(Cl)(2)]Cl (4), Ln(tta)(3)(H2O)(C2H5OH) {Ln = Eu (2), Gd (5)} and Ln(tta)(3)(bpyO2) {Ln = Eu (3), Gd (6)}, were synthesized using 2-thenoyltrifluoroacetone (Htta) as primary ligand and 2,2'-dipyridyl N,N'-dioxide (bpyO2) as neutral donor, and characterized, with special emphasis on their crystal structures and luminescence properties. Single crystal X-ray diffraction revealed that the central metal ion has a coordination number of 9 in 1, and 8 in all other complexes. Complex 3 exhibited a broad excitation spectrum ranging from 250 to 480 nm, exhibiting, when compared to 1 and 2, higher absolute emission quantum yields of 0.46, 0.36 and 0.33, for excitation at 400, 425, and 450 nm, respectively. The theoretical intensity parameters, radiative and non-radiative decay rates, and intrinsic and absolute emission quantum yields were assessed using the LUMPAC software displaying a very good accord with the experimental values. Moreover, organic light-emitting diodes with a maximum efficiency of 5.7 x 10(-2) cd A(-1) at 14 V were fabricated using 3 as an emitting layer.
publisher	WILEY-V C H VERLAG GMBH
issn	1434-1948
isbn	1099-0682
year published	2020
volume	2020
issue	14
beginning page	1260
ending page	1270
digital object identifier (doi)	10.1002/ejic.202000027
web of science category	Chemistry, Inorganic & Nuclear
subject category	Chemistry
unique article identifier	WOS:000516636800001