Comprehensive Study on Nebulizer-Spray-Pyrolyzed Eu-Doped PbS Thin Films for Optoelectronic Applications

Abstract

PbS films in undoped state and with various Eu contents (1 wt.%, 3 wt.%, and 5 wt.%) have been coated effectively on insulating glass substrates by a nebulized spray pyrolysis route. The effects of Eu doping on various properties including the photosensitivity of the PbS films were systematically analyzed. X-ray diffraction (XRD) analysis of the materials revealed a polycrystalline nature with crystallites showing simple cubic structure oriented along (200) direction. Based on the XRD data, the crystallite size, dislocation density, and lattice strain of the films with different doping concentrations were calculated and are consistently discussed. The secondary phase Eu3O4 formed when the Eu doping level was higher in the host solution. The Raman peaks detected at 190 cm−1, 236 cm−1, and 465 cm−1 confirmed formation of PbS. Scanning electron microscopy was used to reveal the morphology of the films as a function of the dopant concentration. Important optical properties including the bandgap, absorption coefficient, dielectric constant, index of refraction, and coefficient of extinction of the films are systematically reported. Optical study of the films revealed a variation of the bandgap from 2.14 eV to 2.81 eV with increasing Eu doping level. The 3 wt.% europium-doped PbS film showed better photosensitivity at 100 W/m2 compared with the other films based on current–voltage (I–V) measurements.