Influence of samarium doping on enhancing the photosensing capability of nebulizer-sprayed bismuth sulfide thin films

The nebulizer spray pyrolysis (NSP) technique is employed to analyze the effect of samarium doping on the structural, morphological, optical, and electrical conductivity in Bi2S3 thin films deposited on bare glass substrates by varying the doping concentration from 0 to 3 wt %. Further, their photosensing properties are also studied to utilize the prepared Bi2S3:Sm thin films for photo-detecting applications. The Bi2S3:Sm thin films are found to be in an orthorhombic structure. The data from X-ray diffraction are used to calculate the value of crystallite size, microstrain, and lattice parameters, as well as the volume of the unit cell. 2% Sm-doped Bi2S3 film exhibited a maximum crystallite size of 38 nm and a lower micro-strain value. FESEM micrographs of 2% Sm-doped film show well-defined larger grains. The optical band gap is found to vary between 2.02 and 2.26 eV when the Sm doping concentration is varied. These thin films' absorption is higher around the ultraviolet region of the electromagnetic spectra. The electrical properties exhibited an increase in photocurrent under illumination. A higher responsivity of 9.57 x 10(-1) AW(-1), detectivity of 1.97 x 10(11) Jones, and external quantum efficiency of 309% are recorded for Bi2S3:Sm (2%) thin film. The response and recovery time of the Bi2S3:Sm (2%)-based photodetector are observed to be 1.6 and 1.8 s, respectively. These favorable characteristics of samarium-doped Bi2S3 thin films recommend its potential usage in low-cost, high-performance UV photodetectors.