Tailoring properties of nano-crystalline CdO thin films by incorporation of Al for enhanced photo-voltaic applications

Abstract

Nano-crystalline thin films of Al doped and undoped CdO thin films were successfully deposited using home-built spray pyrolysis unit. The consequence of Al in CdO was explored and found that the doping of Al has influenced the characteristics of CdO. The CdO was doped with varying concentration of Al viz.0, 0.1, and 10 At.%. The physical, optical and morphological properties were analyzed. These films showed a preferential growth along [111] and [020] direction. The reduction in lattice parameter found to be, the undoped film had lattice parameter of 4.6833×10-10 m whereas, 10 At.% had 4.6819×10-10 m. All crystallites were below 50 nm and grain size was estimated using Scherrer and Williamson-hall plot. The 0.1 At.% of Al showed a larger absorbance whiled 10 At.% had the lowest absorbance. Which is also reflected in transmittance. All film showed transmittance from 70% to 86%. The 10 At.% had the largest transmittance. The reduction in bandgap was observed 10 At.% has the lowest bandgap of 2.04 eV against undoped which has a bandgap of 2.37 eV. The 10 At.% Al film showed an average reflectance of 0.061 at 700 nm whereas; undoped film has an average reflectance of 0.083. The refractive index found to decrease as the doping concentration increases. The electrical conductivity was estimated from optical analysis and found that the electrical conductivity found to increase from 4.7×104 S/cm to 5.2×104 S/cm as the concentration of Al is increased. Haacke’s figures of merit (φH) was calculated and found that doping has increased the φH. 10 At.% showed 8.23×10-3cm-1. Nonlinear optical parameters were also studied. The Scanning electron microgram suggests the incorporation of Al has increased in density of particles in the film. Hence, the developed nano-crystalline CdO thin films by incorporation Al for enhanced photo-voltaic applications.