Improving the FOM of photodetectors fabricated by Sn-doped CuS nanostructures

The Sn-doped CuS nanostructures with different Sn-doping concentrations (Sn₁ (5 %), Sn₂ (10 %), and Sn₃ (15 %)) were synthesized by the sonochemical method. Due to the difference in ionic radii between Cu and Sn, the stress in the CuS crystal was increased from 41 × 10⁻⁴ for the undoped sample to 50 × 10⁻⁴ for the Sn₂-doped sample. The absorption of visible light by the doped samples was increased dramatically. The morphology of CuS nanostructures was changed from nanoparticles (NPs) in the undoped CuS to nanoplates in the Sn₂-doped CuS. Finally, the optoelectronic applications of the samples were studied, and it was shown that all the samples responded to the visible light source, and their resistance was decreased due to light radiation. The results indicated that specific detectivity (D*), responsivity (R), and sensitivity (S) as the figure-of-merit (FOM) of the photodetectors were increased from 2.07 × 10⁹ Jones, 0.92 mA W⁻¹, and 1328 % for undoped CuS nanostructures to 65.22 × 10⁹ Jones, 28.27 mA W⁻¹, and 3802 % for the Sn₂-doped CuS nanostructures. The Mott-Schottky (M − S) results indicated that a higher acceptor carrier concentration in the Sn-doped CuS compared to undoped CuS was one of the most critical factors in enhancing the FOM of the photodetectors fabricated with Sn-doped CuS nanostructures.