Improved opto-electronic properties of Bi2S3 thin films through trivalent atom (Al3+) doping for photodiode applications

Abstract

The present work discloses the development of Bi2S3: Al (0, 1, 3, 5%) thin films using the spray pyrolysis technique for photosensing application. The structural analysis of the prepared samples through XRD revealed the ortho-rhombic structure of Bi2S3 with an increase in crystallite size of 38 nm when doped with Al atoms signifying the incorporation of Al ions in substitutional sites rather than interstitial sites. The optical absorption of the Bi2S3 thin films improved through Al doping and obtained maximum absorption for optimal doping of 3% Bi2S3: Al thin films. Also from Tauc's plot, a decrease in bandgap value of 1.84 eV for the sample was observed with a red shift in the absorption spectrum. The morphological studies showed the samples exhibited distributed candy-shaped grains with uneven morphology and with Al doping the morphology turned to aggregated grain clusters with tiny pinholes or cracks. The photoluminescence study shows two distinct emission peaks around 475 nm and 525 nm due to the blue and green emissions. Finally, the photosensing studies reveal that the 3% Bi2S3: Al photodetector exhibits higher R (4.02 × 10−1 A/W), D* (3.36 × 1010Jones), and EQE (130%) compared to other devices suggesting that the material could be promising for commercial device application.