Thin film solar cell technology has traditionally made use of costly high energy vacuum based processes like sputtering and evaporation. The use of a nanoparticle ink as a precursor absorber layer is a promising route for solution processed photovoltaics which has a number of advantages over vacuum-based methods. Nanoparticle inks are genuine colloidal dispersions that can be deposited through a variety of low cost printing techniques to produce smooth films with mirror-like finishes.

Nanoco has developed a range of CIGS and CIS (copper indium gallium diselenide/sulfide, copper indium diselenide/sulfide) nanoparticle materials with tunable bandgaps ideal for fully exploiting the solar spectrum. The all-important stoichiometry of the final CIGS absorber layer can be built in and finely tuned at the nanoparticle level. This allows a bottom-up approach to creating homogenous CIGS films over large areas, a serious problem for the vacuum-based technologies when scaling up the record lab cell efficiencies.

Nanoco’s flexible synthesis approach can be adapted to a wide range of binary, ternary and quaternary sulphide and selenide particles. After synthesis the nanoparticles are isolated, cleaned and dispersed in solvents to form the nanoparticle ink for coating. The presence of organic ligands attached to the surface of the nanoparticle adds much of the processing functionality to the inorganic semiconductor material. Many characteristics such as the solubility, robustness to agglomeration, particle size control and organic content are dictated by the choice of ligand.