Facile single-component precursor for Cu₂ZnSnS₄ with enhanced phase and composition controllability

A simple and effective method has been demonstrated using soluble single-component precursors to achieve high quality Cu₂ZnSnS ₄ (CZTS) thin films with enhanced phase and composition controllability. The soluble single-component precursors were composed of Cu_2-xS colloidal nanocrystals (NC) and the homogeneously distributed Zn-Sn species on the surface. Zn species is presented as the surface ligand for the first time, in the form of Zn-Sn complex, providing both the colloidal stabilization and the essential components for CZTS. CZTS film composition is governed by the prescribed stoichiometry between Cu_2-xS nanoparticles and the Zn-Sn complex in solution. This novel reaction process enables a favorable CZTS phase progression, with less than 175 °C formation temperature, and a minimized secondary phase growth mode, due to its local composition uniformity in both liquid and film state. Compared with the approaches based on molecular precursor or quarternary CZTS nanocrystals, the single-component precursor allows fine tuning of the kesterite materials for future advanced optoelectronics.