Heteroleptic light-emitting copper(I) complexes with possible applications in LECs and OLEDs

Sarah Keller^a

^aDepartment of Chemistry, University of Basel, Spitalstrasse, 51, Basel, Switzerland

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics 2015 (HOPV15)

Roma, Italy, 2015 May 11th - 13th

Organizer: Filippo De Angelis

Poster, Sarah Keller, 114
Publication date: 5th February 2015

The access to artificial light sources is one of the basic human needs and crucial for our modern society. As the energy to light conversion with “classic” lighting systems is relatively inefficient, the development of new lighting devices such as LECs (Light-Emitting Electrochemical Cells) and OLEDs (Organic Light-Emitting Diodes) promises considerable savings in terms of both energy and resources. The main advantage of this technology lies in the generation of visible light as main product instead of heat with light only as a by-product. This poster will present new results on the synthesis and investigation of light-emitting copper(I) complexes: For LECs, charged complexes with [PF₆]⁻ or other counter ions are required, whereas OLEDs also work with neutral, uncharged compounds. Based on the encouraging results of the Cu(I) complexes with heteroleptic N^N and P^P chelating ligands in our group [1], the strategy is to further modify and fine tune these ligands. Improving the features of the Cu(I) compounds will make them a low-priced alternative to the materials which are based on less abundant elements such as ruthenium or iridium. In order to stabilize the d¹⁰ state of Cu(I) and protect it from being oxidized, the ligands should be coordinated in a tetrahedral geometry. Promising ligands are bisphosphanes such as POP (bis[(2-diphenylphosphino)phenyl] ether) and xantphos (4,5-Bis(diphenylphosphino)-9,9-dimethylxanthene), in combination with 2,2'-bipyridines, 2,2':6',2''-terpyridines and other chelating N-donors. We recently demonstrated that simple structural modification of the bpy ligand leads to improved luminance and efficiency of LECs containing [Cu(POP)(6-Mebpy)][PF₆] and [Cu(POP)(6,6′-Me₂bpy)][PF₆] (6-Mebpy = 6-methyl-2,2′-bipyridine, 6,6′-Me₂bpy = 6,6′- dimethyl-2,2′-bipyridine) [2]. Further alteration of the ligands will provide new insights into their influence on the important complex properties such as electroluminescence, lifetime of the excited state, quantum yield and ion mobility. The sustainability of the luminophores combined with the elegant setup of LECs makes these devices promising candidates for the lighting of the future.
Schematic layout of the LECs that were applied for testing of our compounds. (Luminophore = light-emitting copper(I) complex, BMIM = 1-Butyl-3-methylimidazolium hexafluorophosphate (ionic liquid), PEDOT:PSS = Poly(3,4-ethylenedioxythiophene) Polystyrene sulfonate (polymer mixture))
[1] R. D. Costa, D. Tordera, E. Orti, H. J. Bolink, J. Schönle, S. Graber, C. E. Housecroft, E. C. Constable, J. Zampese, "Copper(I) complexes for sustainable light-emitting electrochemical cells", J. Mater. Chem., Vol. 21, (2011), pp. 16108 - 16118. [2] S. Keller, E. C. Constable, C. E. Housecroft, M. Neuburger, A. Prescimone, G. Longo, A. Pertegás, M. Sessolo, H. J. Bolink: "[Cu(bpy)(P^P)]+ containing light-emitting electrochemical cells: improving performance through simple substitution", Dalton Trans. 2014, 43, 16593-16596.

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