Ultrasonic Spray Pyrolysis Deposited Copper Sulphide Thin Films for Solar Cell Applications

Polycrystalline copper sulphide (Cu(x)S) thin films were grown by ultrasonic spray pyrolysis method using aqueous solutions of copper chloride and thiourea without any complexing agent at various substrate temperatures of 240, 280, and 320°C. The films were characterized for their structural, optical, and electrical properties by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX), atomic force microscopy (AFM), contact angle (CA), optical absorption, and current-voltage (I-V) measurements. The XRD analysis showed that the films had single or mixed phase polycrystalline nature with a hexagonal covellite and cubic digenite structure. The crystalline phase of the films changed depending on the substrate temperature. The optical band gaps (E(g)) of thin films were 2.07 eV (CuS), 2.50 eV (Cu(1.765)S), and 2.28 eV (Cu(1.765)S–Cu(2)S). AFM results indicated that the films had spherical nanosized particles well adhered to the substrate. Contact angle measurements showed that the thin films had hydrophobic nature. Hall effect measurements of all the deposited Cu(x)S thin films demonstrated them to be of p-type conductivity, and the current-voltage (I-V) dark curves exhibited linear variation.