Document Type : Research
Author
Department of Physics- Yazd University
Abstract
Considering the environmental challenges arising from lead toxicity and the poor stability of conventional perovskite solar cells, the development of eco-friendly perovskite alternatives has become a major research priority. In this study, simultaneously investigate the effects of precursor solution concentration and post-deposition annealing temperature on the structural, morphological, and optical properties of spin-coated tin(II) iodide (SnI2) thin films, used as a precursor for lead-free perovskite solar cells. Scanning electron microscopy (SEM) analysis revealed that a precursor concentration of 375 mg/ml SnI2 in precursor solution and annealing at 100 °C provided optimal conditions for producing uniform films with densely packed grains (80–120 nm), controlled porosity, and a significant reduction in surface defects. In contrast, raising the annealing temperature to 150 °C induces thermal degradation and the formation of undesirable anisotropic oxide phases, ultimately reducing both optical and electronic performance. UV–vis spectroscopy confirmed strong absorption edge near 650 nm and the best optical performance was observed for films annealed at 100 °C. Tauc plot analysis determined a direct bandgap of 1.87 eV under optimal conditions accompanied by a reduced Urbach energy of 105 meV, indicating fewer defect states and improved crystallinity. Photoluminescence (PL) spectra further suggested enhanced charge transport and suppressed nonradiative recombination for optimized annealed films. These improvements in morphology and optoelectronic quality make SnI2 thin films annealed at 100 °C as a promising candidate for high-efficiency, lead-free perovskite solar cells, offering a viable strategy to enhance both performance and stability in developing photovoltaic technology.
Keywords
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