SCOPE – Photovoltaic (PV) solar cell technologies are becoming cheaper and more efficient in terms of converting sunlight into electricity. Further progress, with higher efficiencies and lower cost, requires improving current technologies in new ways, whilst using cheap, abundant materials. Kesterites (Cu2ZnSnS(e)4) are one group of promising materials, but it still needs to be established which kind of kesterites is the most suitable and what is the best way to manufacture them.
CONCEPT – Kesterite solar cells are studied as potential top cell absorbers for tandem solar cell applications. Si is the ideal bottom cell candidate, but many of the typical top cell candidates have shortcomings with respect to abundancy, toxicity, stability or cost. Therefore, Cu2ZnSn(S,Se)4 solar cells are considered: they are stable, made from abundant and non-toxic components, and already achieve relatively high performance (i.e. 12.6 %). Unfortunately, they have a too low bandgap (< 1.5 eV), but partially replacing tin atoms with silicon or germanium atoms can potentially increase the bandgap above 1.5 eV. The SWInG consortium focuses both on the development of the processes for the synthesis of wide band gap solar cells based on the Cu2ZnXY4 (with X = Sn, Si, or Ge and Y = S or Se) compounds and on understanding the physical and electrical properties of the high band gap absorber in order to reach high conversion efficiency. The key research challenges are: (i) developing scalable processes for the synthesis of the absorbers; (ii) defining the specifications for high-quality wide band gap absorbers as well as suitable back contact and buffer layers; and (iii) assessing the potential of this technology for PV applications. The wide band gap thin film solar cells developed in this project are expected to reach state-of-the-art efficiencies. Publication of specifications for the synthesis of high quality Cu2ZnXY4 absorber as well as suitable back/front contact are expected. The lead users will be PV module manufacturers and companies that design and produce the equipment for the synthesis of such devices. The results will be disseminated and communicated to the European PV industries and the scientific community. The intensive exchange of researchers between the partners during the project will also lead to an enhanced European collaboration in the research field of thin film solar cells.