Effect of Sulfide Precursor Selection on the Nucleation, Growth, and Elemental Composition of Cu2ZnSnS4 Nanocrystals
文摘
A means to synthesize large quantities of Cu2ZnSnS4 (CZTS) nanocrystals (NCs) is necessary for large-scale production of solution-processed CZTS solar cells. We embarked on a pioneering attempt to investigate and understand the conditions necessary to synthesize CZTS NCs in a novel formamide solvent system using an easily scalable heat-up method and focused on the effect of sulfide precursor selection (thioacetamide vs thiourea). Unlike previous reports, which studied metallic and binary compounds, the compound (CZTS) we investigated comprises more than one metallic element. This difference in composition made possible the observation that sulfide precursor selection strongly alters the elemental composition of the NCs, a vital consideration for multinary compounds of which their performance is strongly dependent on their elemental composition. We found also that sulfide precursor choice influences the nucleation and growth characteristics of the NCs but not the phase of the final product or the phase transformation during reaction. The reasons for the observed differences are investigated and presented. On the basis of these findings, multigram quantities of CZTS NCs with small size and suitable elemental composition, properties crucial for solution-processed CZTS solar cells, are synthesized successfully with high yields.