Heteroleptic bis-diimine copper(I) complexes for applications in solar energy conversion

The development of molecular materials for conversion of solar energy into electricity and fuels is one of the most active research areas, in which the light absorber plays a key role. In this article, we present a class of photo-sensitizers constituted by heteroleptic bis-diimine copper(I) complexes, whose features rely on their tunable MLCT excited states and earth abundant and environmentally friendly nature of copper. These properties make this class of dyes compatible with a sustainable development. Their synthesis through the HETPHEN strategy and the background of their photophysical properties as well as the recent advances in the fields of both dye-sensitized solar cells and photoinduced charge separation are presented. The presented examples prove that bis-diimine copper(I) complexes are valuable dyes to be used to build multicomponent arrays for long range electron transfer and for dye-sensitized solar cells. These examples illustrate that one major advantage of heteroleptic complexes is the possibility to finely tune their opto-electronic properties to a larger extent than homoleptic complexes.