Development of a High-Performance of Cu-Doped SnS Thin Film for Broadband Flexible Photodetector

Tin sulfide, particularly in its π-phase with a cubic crystal structure, has demonstrated significant potential for use in flexible photodetector applications due to its unique optoelectronic properties. However, its performance is often limited by low photocurrent and, consequently, low responsivity. This study addresses this challenge by introducing a novel approach to enhancing photodetector performance through copper doping. A thin film of copper-doped tin sulfide (SnS: Cu) was grown on a flexible polyester substrate using the cost-effective and straightforward chemical bath deposition (CBD) technique. The photoresponse measurements demonstrated an increase in responsivity of approximately 56 times compared to what was previously reported for undoped SnS thin films in our earlier study. Furthermore, the present photodetector exhibited a strong response across a wide range from UV to near-infrared illumination. X-ray diffraction (XRD) confirmed the preservation of the cubic SnS phase. Field emission scanning electron microscopy (FE-SEM) revealed a homogeneous, quasi-spherical grain structure. Energy-dispersive X-ray spectroscopy (EDX) confirmed the presence of Cu in the film, and the systematic shift of XRD peaks toward higher diffraction angles indicates that Cu is incorporated into the SnS lattice, consistent with substitutional doping. The optical measurements indicated a bandgap of 1.44 eV. The responsivity (R) and detectivity (D) were also calculated at 380 nm, 750 nm, and 850 nm. These findings underscore the potential of Cu-doped SnS thin films as next-generation flexible optoelectronic devices.