ABSTRACT
The development of iridium-free, yet efficient emitters with thermally activated delayed fluorescence (TADF) was an important step towards mass production of organic light-emitting diodes (OLEDs). Progress is currently impeded by the low solubility and low chemical stability of the materials. Herein, we present a CuI -based TADF emitter that is sufficiently chemically stable under ambient conditions and can be processed by printing techniques. The solubility is drastically enhanced (to 100â g L-1 ) in relevant printing solvents. The integrity of the complex is preserved in solution, as was demonstrated by X-ray absorption spectroscopy and other techniques. In addition, it was found that the optoelectronic properties are not affected even when partly processing under ambient conditions. As a highlight, we present a TADF-based OLED device that reached an efficiency of 11±2 % external quantum efficiency (EQE).
ABSTRACT
The substitution of rare metals such as iridium and platinum in light-emitting materials is a key step to enable low-cost mass-production of organic light-emitting diodes (OLEDs). Here, it is demonstrated that using a solution-processed, fully bridged dinuclear Cu(I)-complex can yield very high efficiencies. An optimized device gives a maximum external quantum efficiency of 23 ± 1% (73 ± 2 cd A(-1) ).
Subject(s)
Copper/chemistry , Electrical Equipment and Supplies , Organometallic Compounds/chemistry , Models, Molecular , Molecular Conformation , TemperatureABSTRACT
Luminescent Cu(I) complexes are interesting candidates as dopants in organic light-emitting diodes (OLEDs). However, open questions remain regarding the stability of such complexes in solution and therefore their suitability for solution processing. Since the emission behavior of Cu(I) emitters often drastically differs between bulk and thin film samples, it cannot be excluded that changes such as partial decomposition or formation of alternative emitting compounds upon processing are responsible. In this study, we present three particularly interesting candidates of the recently established copper-halide-(diphenylphosphino)pyridine derivatives (PyrPHOS) family that do not show such changes. We compare single crystals, amorphous bulk samples, and neat thin films in order to verify whether the material remains stable upon processing. Solid-state nuclear magnetic resonance (MAS (31)P NMR) was used to investigate the electronic environment of the phosphorus atoms, and X-ray absorption spectroscopy at the Cu K edge provides insight into the local electronic and geometrical environment of the copper(I) metal centers of the samples. Our results suggest that--unlike other copper(I) complexes--the copper-halide-PyrPHOS clusters are significantly more stable upon processing and retain their initial structure upon quick precipitation as well as thin film processing.
Subject(s)
Copper/chemistry , Pyridines/chemistry , Magnetic Resonance Spectroscopy , Solutions , X-Ray Absorption SpectroscopyABSTRACT
Easy come, easy go: the great structural diversity of Cu(I) complexes is an ambivalent trait. Apart from the well-known catalytic properties of Cu(I), a great number of potent luminescent complexes have been found in the last ten years featuring a plethora of structural motifs. The downside of this variety is the undesired formation of other species upon processing. In here, strategies to avoid this behavior are presented: Only one favorable structural unit often exists for multinuclear Cu(I) complexes with bridging ligands. In addition, these complexes exhibit favorable photophysical properties due to cooperative effects of the metal halide core. Furthermore, we demonstrate the broad range of applications of emitting Cu(I) compounds.
Subject(s)
Coordination Complexes/chemistry , Copper/chemistry , Ligands , Molecular Conformation , Nitrogen/chemistry , Phosphines/chemistry , Quantum Theory , Spectrometry, FluorescenceABSTRACT
o-Bromo(propa-1,2-dien-1-yl)arenes exhibit novel and orthogonal reactivity under Pd catalysis in the presence of secondary amines to form enamines (concerted Pd insertion, intramolecular carbopalladation, and terminative Buchwald-Hartwig coupling) and of amides to form indoles (addition, Buchwald-Hartwig cyclization, and loss of the acetyl group). The substrates for these reactions can be accessed in a reliable and highly selective two-step process from 2-bromoaryl bromides.
