Brightly blue and green emitting Cu(I) dimers for singlet harvesting in OLEDs

Experimental and theoretical studies of highly emissive dinuclear Cu(i) halide complexes with delayed fluorescence

Experimental and theoretical studies of the photophysical properties of three novel emissive dinuclear Cu(i) halide complexes with thermally activated delayed fluorescence (TADF) are reported.

Dual luminescence in solid CuI(piperazine): hypothesis of an emissive 1-D delocalized excited state

Dual luminescence in crystals of [CuI(piperazine)_0.5]_∞ has been photophysically characterized and discussed on the basis of TD-DFT theoretical calculations.

Structures and photophysical properties of copper(i) complexes bearing diphenylphenanthroline and bis(diphenylphosphino)alkane: the effect of phenyl groups on the phenanthroline ligand

Emissive copper(i) complexes bearing a phenanthroline ligand having diphenyl groups and diphosphines were synthesized. The quantum yields are enhanced by the diphenyl groups on the phenanthroline ligand.

Four highly efficient cuprous complexes and their applications in solution-processed organic light-emitting diodes

Four novel highly emissive cuprous complexes were prepared. The OLEDs from these complexes had a peak current efficiency of 17.8 cd A⁻¹ and an EQE of 6.4%.

A new class of deep-blue emitting Cu(i) compounds – effects of counter ions on the emission behavior

A series of three deep-blue emitting Cu(i) compounds with a tripodal ligand is investigated. The compounds only deviate by their respective counter anions. These anions have a significant impact on the emission behavior.

Halocuprate(i) zigzag chain structures with N-methylated DABCO cations – bright metal-centered luminescence and thermally activated color shifts

Two halocuprate(i) chain structures were synthesized and studied with respect to their emission properties that are governed by two interacting chain segments.

Thermally activated delayed fluorescence materials towards the breakthrough of organoelectronics

The design and characterization of thermally activated delayed fluorescence (TADF) materials for optoelectronic applications represents an active area of recent research in organoelectronics. Noble metal-free TADF molecules offer unique optical and electronic properties arising from the efficient transition and interconversion between the lowest singlet (S1 ) and triplet (T1 ) excited states. Their ability to harvest triplet excitons for fluorescence through facilitated reverse intersystem crossing (T1 →S1 ) could directly impact their properties and performances, which is attractive for a wide variety of low-cost optoelectronic devices. TADF-based organic light-emitting diodes, oxygen, and temperature sensors show significantly upgraded device performances that are comparable to the ones of traditional rare-metal complexes. Here we present an overview of the quick development in TADF mechanisms, materials, and applications. Fundamental principles on design strategies of TADF materials and the common relationship between the molecular structures and optoelectronic properties for diverse research topics and a survey of recent progress in the development of TADF materials, with a particular emphasis on their different types of metal-organic complexes, D-A molecules, and fullerenes, are highlighted. The success in the breakthrough of the theoretical and technical challenges that arise in developing high-performance TADF materials may pave the way to shape the future of organoelectronics.

Phosphorescence versus thermally activated delayed fluorescence. Controlling singlet-triplet splitting in brightly emitting and sublimable Cu(I) compounds

Photophysical properties of two highly emissive three-coordinate Cu(I) complexes, (IPr)Cu(py2-BMe2) (1) and (Bzl-3,5Me)Cu(py2-BMe2) (2), with two different N-heterocyclic (NHC) ligands were investigated in detail (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene; Bzl-3,5Me = 1,3-bis(3,5-dimethylphenyl)-1H-benzo[d]imidazol-2-ylidene; py2-BMe2 = di(2-pyridyl)dimethylborate). The compounds exhibit remarkably high emission quantum yields of more than 70% in the powder phase. Despite similar chemical structures of both complexes, only compound 1 exhibits thermally activated delayed blue fluorescence (TADF), whereas compound 2 shows a pure, yellow phosphorescence. This behavior is related to the torsion angles between the two ligands. Changing this angle has a huge impact on the energy splitting between the first excited singlet state S1 and triplet state T1 and therefore on the TADF properties. In addition, it was found that, in both compounds, spin-orbit coupling (SOC) is particularly effective compared to other Cu(I) complexes. This is reflected in short emission decay times of the triplet states of only 34 μs (1) and 21 μs (2), respectively, as well as in the zero-field splittings of the triplet states amounting to 4 cm(-1) (0.5 meV) for 1 and 5 cm(-1) (0.6 meV) for 2. Accordingly, at ambient temperature, compound 1 exhibits two radiative decay paths which are thermally equilibrated: one via the S1 state as TADF path (62%) and one via the T1 state as phosphorescence path (38%). Thus, if this material is applied in an organic light-emitting diode, the generated excitons are harvested mainly in the singlet state, but to a significant portion also in the triplet state. This novel mechanism based on two separate radiative decay paths reduces the overall emission decay time distinctly.

Bright coppertunities: multinuclear Cu(I) complexes with N-P ligands and their applications

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.

Simple and extremely efficient blue emitters based on mononuclear Cu(i)-halide complexes with delayed fluorescence

Mononuclear Cu(i)-halide complexes with a ternary ligand system exhibit blue light emission based on delayed fluorescence with extremely high quantum yields, approaching 100% in the solid states.

DFT/TDDFT insights into the chemistry, biochemistry and photophysics of copper coordination compounds

Highlighting the recent progress in DFT/TDDFT application to coordination chemistry of copper.

Control of emission colour with N-heterocyclic carbene (NHC) ligands in phosphorescent three-coordinate Cu(i) complexes

A series of three phosphorescent mononuclear (NHC)–Cu(i) complexes were prepared and characterized.

Charge-transfer metal–organic frameworks based on CuCN architecture units: crystal structures, luminescence properties and theoretical investigations

Four cuprous cyanide charge-transfer metal–organic frameworks have been fabricated via the synchronous redox and self-assembly reaction, and exhibit intense green luminescence properties and high thermal stabilities.