Synthesis of thermally stable Cu3SbS4 thin films with high charge density: Doping of Sb atoms in hexagonal Cu9S5 close-packed planes

Abstract

Cu₃SbS₄ is commonly used as a hole transport layer in heterojunction devices due to its high valence vacancy, which provides a large number of carriers. The preparation of Cu₃SbS₄ by large-scale dry chemistry is often accompanied by the generation of other copper antimony sulfide ternary phases during the heating process. By exploiting phase transitions in the crystal structure, the synthesis of nanophases can be controlled to improve the properties of the material. Different choices of the main material structure can trigger the evolution of the internal structure of the product material. In the experiment, the fusion of antimony atoms with host Cu₉S₅ crystals will preferentially produce thermally stable Cu₃SbS₄. The stepwise synthesis of Cu₃SbS₄ films from Sb-Cu₉S₅ stacked films was discovered. The influence of reaction temperatures on crystal structure, surface morphology, chemical composition of the films was investigated, and the optical and electrical properties of the films were analyzed during the alloying process. The pure Cu₃SbS₄ was obtained by heating and melting Cu₉S₅ and Sb in a sulphur vapor environment. The Cu₃SbS₄ films obtained at 450 °C have a forbidden bandwidth of 0.89 eV and a charge density of 1.39 × 10²⁰ cm⁻³. These findings provide an explanation for the phase transition and morphological changes during the synthesis of copper antimony sulphide and offer a new thinking strategy for the alloying of synthetic ternary copper-based sulphides.