Effect of Cr Doping Concentration on the Structural, Optical, and Electrical Properties of Lead Sulfide (PbS) Nanofilms

In this paper, pristine and Cr-doped lead sulfide (PbS) nanofilms were prepared by chemical and deposition methods. From X-ray diffraction (XRD) analysis, all nanofilm samples possessed good crystallinity with a preferential orientation of the (200) crystal plane. As the Cr doping concentration increased, the nanofilm grain size decreased from 71.5 to 18.9 nm. The SEM results revealed that the variation in Cr concentration led to different grain shapes, and the grain size became smaller with the increasing doping concentrations. Optical studies showed that the optical band gap of PbS films increased from 1.21 to 1.60 eV after Cr doping due to the quantum confinement effect; the 2% Cr-doped PbS nanofilm, with an Eg of 1.49 eV, matched the ideal band-gap value. The electrical characterization showed that, for a 2% Cr doping concentration, the Hall mobility and volume carrier concentration of the nanofilm reached the maximum values of 59.6 cm2∙V−1 s−1 and 20.7 × 1016 cm−3 respectively. The 2 at.% Cr-doped PbS nanofilms exhibited the best optical and electrical properties, suitable for solar cell applications.