Open Access

ARTICLE

Spin-Coated Kesterite Based CZTS (Cu₂ZnSnS₄) Thin Films: Structural, Optical, and Compositional Analysis for Photovoltaic Applications

Md. Rakib Hasan¹, Afrina Sharmin², Mimi Mondal^1,3, Md. Ahasan Habib¹, Rinku Majumder¹, Muhammad Shahriar Bashar^2,*, Md. Salahuddin Mina^1,*

1 Physics Discipline, Science, Engineering and Technology School, Khulna University, Khulna, Bangladesh
2 Institute of Energy Research and Development (IERD), Bangladesh Council of Scientific and Industrial Research (BCSIR), Dhaka, Bangladesh
3 Department of Physics, Faculty of Arts and Science (FSA), Bangladesh Army University of Science and Technology, Khulna, Bangladesh

* Corresponding Authors: Muhammad Shahriar Bashar. Email: ; Md. Salahuddin Mina. Email:

Chalcogenide Letters 2026, 23(3), 1 https://doi.org/10.32604/cl.2026.079270

Received 18 January 2026; Accepted 03 March 2026; Issue published 03 April 2026

Abstract

In this work, spin-coated Cu₂ZnSnS₄ (CZTS) thin films with systematically varied thicknesses were investigated to understand their influence on structural, compositional, and optical properties relevant to high-performance photovoltaic applications. CZTS absorber layers were fabricated using a sol-gel spin-coating technique, which offers simplicity, low cost, and excellent thickness control, followed by annealing at 450°C under a nitrogen atmosphere to promote crystallization and phase formation. X-ray diffraction (XRD) analysis revealed that films with a thickness of approximately 608 nm exhibited the highest crystallinity and a preferred orientation along the (112) plane, indicating enhanced structural order and improved grain connectivity. Raman spectroscopy further confirmed the formation of single-phase kesterite CZTS, with no detectable secondary phases, ensuring material purity. Scanning electron microscopy (SEM) images demonstrated compact, uniform grains, while energy-dispersive X-ray spectroscopy (EDX) analysis indicated a slightly Cu-rich and Zn-poor composition, consistent with typical solution-processed CZTS films. Optical characterization using UV-Vis spectroscopy revealed strong absorption in the visible region, with absorption coefficients exceeding 10⁴ cm⁻¹, highlighting the material’s suitability for efficient light harvesting. The direct optical bandgap was estimated to range from 1.48 to 1.53 eV, achieving an optimal value of 1.50 ± 0.02 eV for the ten-layer film. Urbach energy values (0.57–0.78 eV) suggested the presence of defect-related localized states associated with grain boundaries and compositional variations. Overall, this work demonstrates that careful thickness optimization significantly enhances the microstructural, compositional, and optical properties of CZTS thin films, providing valuable insights for the design, fabrication, and optimization of efficient kesterite-based photovoltaic absorber layers for practical solar cell applications.

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