Correlation and optimization of the optoelectrical properties of DC magnetron-sputtered Cu2ZnSnS4 absorber layer as a function of the material composition

Abstract Sequential DC magnetron sputtering and rapid thermal processing appear very promising to fabricate CZTS-based thin-film photovoltaic (PV) solar cells with regards to existent environmental and industrial issues. However, their state-of-the-art efficiency remains limited to about 10% to date. In this work, we aim at optimizing the optical and electrical properties of the CZTS absorber by an extensive screening of their correlation with the material composition. This is widely varied by different deposition (i.e. thickness of precursors) and process (i.e. RTP) conditions. We assess the impact of absorber composition on the energy bandgap, absorption coefficient, p-type carrier concentration and mobility. The most important results lie in the extensive analysis of the inverse power-law trend for carrier concentration versus mobility and logarithmic trend versus bandgap. Our conclusions point the optimal composition ratios towards Cu-poor and less than actual target Zn-rich range. As a result, a potential roadmap is drawn up based on presented experimental results and SCAPS simulations in order to reach more than 10% cell efficiency with the target technology.