Electrospun Cu2ZnSnS4 microfibers with strong (112) preferred orientation: fabrication and characterization

Abstract

In this study, Cu₂ZnSnS₄ (CZTS) microfibers were fabricated using a non-vacuum method of electrospinning following vulcanization process. CZTS fibers were obtained via the vulcanization of the electrospun precursor fibers at 500 °C (CZTS-500), 550 °C (CZTS-550), and 600 °C (CZTS-600), in sulfur ambient conditions. Samples were characterized by scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), XRD mapping scan, Raman spectrum and UV-vis absorption. Polycrystalline CZTS fibers with kesterite crystallization were formed in CZTS-500, whereas higher temperature vulcanization in CZTS-550 led to a strong preferential crystallization along CZTS [112] crystal direction around fiber surface, which is definitely confirmed by XRD mapping scan. More interestingly, the band gap value (E_g), which was 1.48 eV for CZTS-500, reduced to 1.43 eV for CZTS-550. E_g reduction may be related to lattice distortion induced by stress or strain around fiber surface, and can be beneficial for broadening optical absorption range thus increasing the efficiency of CZTS-based solar cells.