Insight into the Growth Mechanism of Mixed Phase CZTS and the Photocatalytic Performance

In this work, CZTS particles with a mixed phase of wurtzite and kesterite were synthesized by the solvothermal method. The time-dependent XRD patterns, Raman spectra, SEM, and EDS analysis were employed to study the growth mechanism of CZTS. The results revealed that the formation of CZTS started from the nucleation of monoclinic Cu₇S₄ seeds, followed by the successive incorporation of Zn²⁺ and Sn⁴⁺ ions. Additionally, the diffusion of Zn²⁺ into Cu₇S₄ crystal lattice is much faster than that of Sn⁴⁺. With increasing time, CZTS undergoes a phase transformation from metastable wurtzite to steady kesterite. The morphology of CZTS tends to change from spherical-like to flower-like architecture. The mixed-phase CZTS with a bandgap of 1.5 eV exhibited strong visible light absorption, good capability for photoelectric conversion, and suitable band alignment, which makes it capable to produce H₂ production and degrade RhB under simulated solar illumination.