Unveiling strain-driven band gap tunability in low-temperature CBD CdS thin films

Engineering notes

Engineering notes will be added by the Power for Solar editorial team.

Chinese explanation / 中文解读

中文解读待补充：本站会优先为光伏效率、钙钛矿太阳能电池、储能技术、太阳能热利用、BIPV、并网技术等高价值论文补充中文说明。

Original abstract

Abstract The impact of residual strain on the optical band gap of cadmium sulfide (CdS) thin films synthesized by chemical bath deposition (CBD) is systematically investigated. CdS, a II–VI semiconductor, is widely employed in photovoltaics and optoelectronics devices; however, precise control of its band gap remains essential for optimizing light absorption, carrier transport, and device efficiency. The novelty of the present work lies in establishing a direct quantitative correlation between residual lattice strain and optical band-gap modulation in CBD-grown CdS thin films, thereby demonstrating strain engineering as an effective alternative to conventional doping and high-temperature processing techniques. Variations in bath temperature, solution pH, precursor concentration, and deposition duration were utilized to induce controlled microstructural stress, resulting in different levels of residual strain within the crystallites. Lattice strain and crystallite size were evaluated using the Scherrer method and high-resolution X-ray diffraction analysis, while scanning electron microscopy revealed progressive grain coalescence and time-dependent morphological evolution. UV–Vis absorption spectroscopy and Tauc plot analysis demonstrated a strong dependence of the optical band gap on the induced strain state. Compressive strain was found to increase the band-gap energy through bond-length contraction and crystal-field effects, whereas tensile strain produced a comparatively smaller reduction in the band gap. The study provides new insights into the strain–structure–property relationship in CdS thin films and highlights residual strain as a controllable parameter for tailoring optoelectronic properties. These findings offer a sustainable and cost-effective route for band-gap engineering of CdS absorber and window layers, paving the way for the development of high-performance solar cells, photodetectors, and other optoelectronic devices without relying on toxic dopants or energy-intensive fabrication processes.

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