Facile low temperature development of Ag-doped PbS nanoparticles for optoelectronic applications

The present article is based on Silver (Ag) doped Lead sulfide (PbS) nanoparticles for optoelectronic applications. Structural and morphological properties of pristine PbS and 0.5, 1.0, 2.5 and 5.0 wt% Ag doped PbS nano -particles (NPs) were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. X-ray diffraction (XRD) patterns of pure PbS, 0.5, 1.0, and 2.5 wt% Ag: PbS NPs were marginally shifted towards a lower diffraction angle and XRD profile of 5.0 wt% Ag: PbS NPs was shifted to the right side with respect to JCPDS card. The crystallite sizes of pristine PbS and Ag: PbS NPs were obtained in the range of 17-18.7 nm. The phase and substitution of Ag into the PbS lattice were confirmed by the Fourier transform (FT) Raman spectra of Ag:PbS NPs. Scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) spectroscopy was employed to observe the morphology and to confirm the homogeneous doping of pristine PbS and Ag-doped PbS NPs. The optical band gaps were determined in the range of 3.011-3.378 eV and 1.201-1.286 eV, respectively from diffused reflectance spectra of pristine PbS and Ag: PbS NPs. Urbach energies were evaluated as 1.5687, 1.8879, 2.8020, 1.6425, and 1.2799 eV from the slopes of the fitted straight lines near the absorption band edge region of pure, 0.5, 1.0, 2.5, and 5.0 wt %, respectively. Current (I)-voltage (V) characteristics of the prepared NPs were carried out in the presence of an applied voltage (+/- 4 V). The enhancement in I-V characteristics of 2.5 and 5.0 wt % was caused by the increment in the injected charge density. The optical transition states were examined by the second-order derivative of the absorbance spectra. The high carrier density in Ag: PbS has been attributed to the bottleneck effect, which is confirmed by the BM shift and I-V characteristics. It was found that Ag: PbS NPs exhibited an increase in electrical properties compared to the pristine PbS NPs.