1：Experimental Design and Method Selection

PbS films were fabricated on glass by simple spray method using nebulizer. The doping percentage of Cu was increased from 0% to 8% in steps of 2%. All other deposition parameters were kept constant.

2：Sample Selection and Data Sources

Lead nitrate (PbNO3) as a source for Pb and thiourea (CS(NH2)2) as a source for S were used to deposit the PbS thin films. The prepared solution was sprayed as pure and added dopant Cu precursor of concentrations 2%, 4%, 6% and 8wt.%.

3：List of Experimental Equipment and Materials

Nebulizer spray gun, Lambda Perkin Elmer UV-Vis-NIR Spectrophotometer, PAN analytical X’Pert Pro XRD, EVO 18 ZEISS scanning electron microscope, Atomic Force Microscopy (AFM), spectrofluorometer, Hall Effect measurement setup, Keithley source meter (Model-2450).

4：Experimental Procedures and Operational Workflow

The prepared solution was sprayed on the substrate surface. The nebulizer spray gun was with a programmed stepper motor system which was moved in x-y direction to attain uniform films. Later the prepared Cu:PbS films were cooled to room temperature and characterized for various studies.

5：Data Analysis Methods

The optical band gap was calculated using absorption measurement spectrum by the Tauc relation. The crystalline size (D), strain (ε) and dislocation-density (δ) of Cu:PbS thin films were determined using specific equations.