A series of highly luminescent, heteroleptic copper(I) complexes has been synthesized using a modular approach based on easily accessible P^N ligands, triphenylphosphine, and copper(I) halides, allowing for an independent tuning of the emission wavelength with low synthetic efforts. The molecular structure has been investigated via X-ray analysis, confirming a dinuclear copper(I) complex consisting of a butterfly shaped metal-halide cluster and two different sets of ligands. The bidentate P^N ligand bridges the two metal centers and can be used to tune the energy of the frontier orbitals and therefore the photophysical characteristics, as confirmed by emission spectroscopy and theoretical investigations, whereas the two monodentate triphenylphosphine ligands on the periphery of the cluster core mainly influence the solubility of the complex. By using electron-rich or electron-poor heterocycles as part of the bridging ligand, emission colors can be adjusted, respectively, between yellow (581 nm) and deep blue (451 nm). These complexes have been further investigated in particular with regard to their photophysical properties in thin films and polymer matrix as well as in solution. Furthermore, the suitability of this class of materials for being applied in organic lightemitting diodes (OLEDs) has been demonstrated in a solution-processed device with a maximum current efficiency of 9 cd/A and a low turn-on voltage of 4.1 V using a representative complex as an emitting compound.

Organic light-emitting diodes (OLEDs) are currently being commercialized for lighting and display applications, but more work has to be done. In addition to the ongoing optimization of materials and devices in terms of efficiency and lifetime, the substitution of processing steps involving vacuum deposition for solution processing techniques is favorable. To reach this aim, good soluble materials are required. A modular family of highly emissive PyrPHOS-copper iodide complexes featuring various ancillary phosphine ligands has been synthesized. Photoluminescence spectroscopy, TCSPC (time-correlated single photon counting), cyclic voltammetry, X-ray diffraction, and DFT calculations were performed to gain a broad understanding of the complexes. While the photophysical properties are consistent within the family, thermal stability and solubility depend on the ligands. The materials showed very high photoluminescence quantum efficiencies up to 99% in powders and 85% in thin films. Selected examples were tested in devices, confirming the suitability of heteroleptic PyrPHOS-complexes for OLEDs.

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) ).

Strongly luminescent, neutral copper(I) complexes bearing 5-(2-pyridyl)tetrazolate and various phosphine ligands were synthesized. While the cationic copper(I) precursors 1b-4b do not exceed photoluminescence quantum yields (PLQY) of 4-46%, the neutral complexes 1a-4a show PLQYs of up to 89%.