A heating-up method for the synthesis of pure phase kesterite Cu2ZnSnS4 nanocrystals using a simple coordinating sulphur precursor

Abstract

Pure phase kesterite Cu₂ZnSnS₄ (CZTS) nanocrystals (NCs) have been successfully synthesized via a heating-up method utilizing metal salts as cation sources and thioacetamide (TAA) as a coordinating sulphur precursor in combination with oleylamine (OAm) as a coordinating ligand and solvent. The slower release of H₂S from the metal–TAA complexes, as compared with the commonly used sulphur powder, is crucial for control of the grain size and size distribution of the NCs. As dominating coordinating ligands, OAm led to Sn-rich nuclei and kesterite CZTS NCs. The formation of pure phase kesterite CZTS NCs depends significantly on the temperature and Zn²⁺/Sn⁴⁺ molar ratio of the reaction system. The formation mechanism of the pure phase kesterite CZTS NCs has been clarified taking into account the chemical potentials of the elements involved.