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.