Molecular Construction Kit for Tuning Solubility, Stability and Luminescence Properties: Heteroleptic MePyrPHOS-Copper Iodide-Complexes and their Application in Organic Light-Emitting Diodes

Abstract

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.