Effect of Stacking Order on the Formation of Cu₂CdSnS₄ Thin Films Synthesized Using Thermal Evaporation Technique

This study investigates the influence of stacking order and sulfurization temperatures on the structural, morphological, optical, and electrical properties of Cu₂CdSnS₄ (CCTS) thin films synthesized via sequential thermal evaporation. Three different stacking sequences (SLG/CdS/Sn/Cu, SLG/Cu/Sn/CdS, and SLG/Cu/CdS/Sn/Cu) were used, followed by sulfurization at 550 and 580 °C. Structural analysis confirmed a tetragonal crystal structure with preferred orientation along the (112) plane, with the N3 series (SLG/Cu/CdS/Sn/Cu) free of SnS impurities. Increasing sulfurization temperature improved crystallinity, increased crystallite size, and reduced lattice strain and dislocation density. Morphological studies showed uniform, crack-free films, with the N3 series exhibiting near-ideal stoichiometry. Optical analysis revealed band gaps in the range of 1.32-1.37 eV, with lower band gap values for higher sulfurization temperatures. Electrical measurements demonstrated that N3-550 had the highest carrier concentration (3.5 × 10¹⁴ cm⁻³) and p-type conductivity, making it the most suitable candidate for photovoltaic applications. The study’s novel approach in stack order optimization and temperature control during sulfurization has resulted in high-quality CCTS thin films with properties that are highly desirable for photovoltaic applications.