Experimental and simulation study for an improved efficiency of 8.46% of a CTS thin-film solar cell: impact of tin (Sn) concentration on structural, optoelectronic properties and photovoltaic performance

In this study, we investigated the influence of tin concentration on the physical properties of eco-friendly CTS thin-film based solar cells deposited by means of the SILAR route. The results were discussed through several characterization techniques. XRD revealed the formation of Cu₂SnS₃ phase, along with peaks of CuS and Cu₄S₇ secondary phases, which diminished with increasing tin concentration. Raman spectroscopy confirmed the tetragonal crystalline structure of CTS films with (112) as the preferred orientation. The direct optical bandgap energy of the synthesized CTS films increased from 1.42 to 1.56 eV as the concentration of tin rose from 0.08 to 0.12 M. Electrical Hall effect measurements performed on the grown CTS layers revealed a p-type conductivity with hall mobility in the range 0.38–2.135 cm²/Vs and a carrier concentration between 3.93 × 10²¹ cm⁻³ and 7.68 × 10²¹ cm⁻³. Furthermore, using SCAPS-1D solar cell simulation software, the photovoltaic performance of the CTS-S1, CTS-S2 and CTS-S3 absorber layers has been evaluated. Despite the fact that the CTS-S1 absorber layer has more secondary phases and slightly lower mobility than the CTS-S2 and CTS-S3 layers, its excellent optical properties, including a high absorption coefficient (> 10⁴ cm⁻¹) and an optimal bandgap energy of 1.42 eV, enabled it to achieve the best efficiency of 8.46%.