Abstract EN:

Copper-Zinc-Tin chalcogenide (Cu2ZnSnS4, CZTS) materials have attracted increasing attention for solar cell absorber layers. To address the issue of low-cost photovoltaic, non-vacuum ink-based approaches were developed involving nanocrystals building blocks. Here, various nanocrystals fabrication process routes are proposed yielding CZTS nanocrystals exhibiting different physicochemical characteristics. A first process is designed to employ a simple sulfide source such as thiourea which advantageously acts both as a complexing agent inhibiting crystallite growth and as a surface additive providing redispersion in polar solvents. We demonstrate the production of solvent-dispersible partially crystallized CZTS nanocrystals via a temperature poly-condensation route involving ((Cu2+)a (Zn2+)b (Sn4+)c (Tu)d (OH-)e )t+ (Tu = CS(NH2)2,thiourea) tailored complex precursors. A second high temperature synthetic procedure performed at higher temperature in molten salts (T > 400 °C) and involving an in-situ generated gas as a template is reported with the objective to minimize defects concentration into the bulk and at the surface of the semiconducting CZTS nanocrystals, Using highly concentrated free SCN--containing reaction mixtures which enhance CZTS precipitation over concurrent reactions, it is demonstrated that this high temperature synthetic route yields highly crystallized CZTS nanocrystals. The versatility of this second process route was demonstrated to the synthesis of Ga doped -CZTS nanocrystals. Lastly, a third process route is reported involving dissolution reprecipitation to the fabrication of CZTS nanocrystals exhibiting platelet morphology. The ability to control crystallinity, morphology and size of the CZTS nanocrystals will provide with an opportunity to further test the effects of these powder characteristics on forming and sintering behaviors of CZTS based films and will greatly help to the further fabrication of low cost solar cells.