Improvement of Structural and Optical Properties of V ⁺ ‐Implanted CZTS Thin Films at Different Fluences

This study investigates the effects of vanadium ion implantation on pristine copper zinc tin sulphide (CZTS) thin films. The CZTS thin films were synthesized via a two‐stage process: electron beam deposition of metal precursors (Cu, Zn, and Sn) followed by sulphurization in a tube furnace at 500°C for 30 min. The as‐grown films were subsequently implanted with 150 keV V ⁺ ions at fluences of 1 × 10 ¹⁶ , 3 × 10 ¹⁶ , and 1 × 10 ¹⁷ ions/cm ² . Structural and optical properties, i.e., key parameters governing photovoltaic performance, were characterized for both pristine and ion‐implanted films using X‐ray diffraction (XRD), Raman spectroscopy, and UV‐Vis spectroscopy. XRD analysis confirmed kesterite CZTS as the dominant phase. Following ion implantation, the kesterite structure was preserved across all fluences; however, diffraction peak shifts revealed tensile stress at 3 × 10 ¹⁶ ions/cm ² and compressive stress at both 1 × 10 ¹⁶ and 1 × 10 ¹⁷ ions/cm ² . Raman spectroscopy revealed prominent peaks in the range of 332–337 cm ⁻¹ , consistent with single‐phase CZTS of kesterite structure. Additionally, traces of a ZnS secondary phase were detected in samples implanted at 1 × 10 ¹⁶ and 3 × 10 ¹⁶ ions/cm ² ; this secondary phase was absent at the highest fluence of 1 × 10 ¹⁷ ions/cm ² . UV‐Vis spectroscopy showed variation in the optical band gap across samples: 1.60 eV for pristine CZTS and 1.61, 1.83, and 1.45 eV for samples implanted at 1 × 10 ¹⁶ , 3 × 10 ¹⁶ , and 1 × 10 ¹⁷ ions/cm ² , respectively. Despite the band gap fluctuation, all values fall within the accepted range for CZTS absorber layers, confirming the material's suitability for photovoltaic applications. Notably, the sample implanted at the highest fluence exhibited the most promising optical properties.