Synthesis and Characterization of Heteroleptic Copper(I) Complexes for Application in Light-Emitting Electrochemical Cells

Light-emitting electrochemical cells (LECs) are a solid-state lighting technology, which has great assets in applications as versatile ‘low-tech’ components. The simple device architecture allows for low-cost device fabrication and manufacturing on flexible substrates and large surfaces. The LEC features several other advantages such as a low turn-on voltage and high power-efficiency and a wide range of emitted colours of light are possible by choosing appropriate emitter compounds. In Chapter 1, the history of artificial lighting and a comparison of different lighting fixtures and display technologies are presented. Along, the advantages and challenges of the LEC technology are discussed and compared to state-of-the-art industrial lighting devices like OLEDs and LEDs. Throughout the projects presented in this thesis, heteroleptic copper(I) complexes are synthesized and characterized for the application as luminophores in the active layer of the LEC device. The complexes are of the type [Cu(PˆP)(NˆN)][A], where PˆP is a chelating bisphosphane and NˆN is a chelating diimine ligand. The common goal of the projects presented in this thesis was the systematic optimization of the luminescence properties of the complexes and finding methods to improve the performance of the LEC device. Heteroleptic copper(I) complexes were chosen as the active species to enable using highly abundant and inexpensive raw materials for the preparation of the active emitter compounds in the LEC. In Chapter 2, the preparation and characterization of a series of [Cu(PˆP)(NˆN)][A] complexes and ionic liquids featuring different ion pairings for the application in the active layer of the LEC are described. Both the photophysical properties of the emitters and the device performance are investigated in depth. Chapter 3 details the preparation of 2,2’-bipyridine-derived ligands with different sterically demanding functional groups in the 6- and 6,6’-positions of the ligand backbone. These ligands are then used to prepare heteroleptic copper(I) complexes of the type [Cu(PˆP)(NˆN)][PF6], which are characterized in their structural and photophysical properties. In Chapter 4, the preparation and characterization of multinuclear copper(I) complexes is presented in order to investigate the effect of multiple d10 metal centres on the structural and emissive properties of the complexes. Chapter 5 describes an approach to influence the electronic properties of the [Cu(NˆN)(PˆP)][PF6] complexes via introduction of electron withdrawing substituents to the NˆN ligand backbone. A last Chapter summarizes the conclusions and findings of the thesis with a brief outlook for each project.