Compositional dependence of optical and electrical properties of indium doped zinc oxide (IZO) thin films deposited by chemical spray pyrolysis

Highlights: • Indium doped ZnO thin films were deposited via chemical spray pyrolysis. • ZnO thin films were doped with different Indium concentrations. • Crystallinity decreased with increasing Indium concentrations. • Surface morphology was influenced by varying dopant concentrations. • The 4 at.% Indium doping sample showed the lowest resistivity. The structural and optoelectronic properties of undoped and indium doped zinc oxide (IZO) thin films grown on glass substrates through a simple reproducible custom-made pneumatic chemical spray pyrolysis technique are presented. X-ray diffraction (XRD) results showed a polycrystalline structure of hexagonal wurtzite phase growing preferentially along the (002) plane for the undoped sample. Increase in dopant content modified the orientation leading to more pronounced (100) and (101) reflections. Optical transmission spectra showed high transmittance of 80–90% in the visible range for all thin films. The optical band gap energy (E_g) was evaluated on the basis of the derivative of transmittance (dT/dλ) versus wavelength (λ) model and Tauc's extrapolation method in the region where the absorption coefficient, α ≥ 10⁴ cm⁻¹. The observed values of E_g were found to decrease generally with increasing In dopant concentration. From the figure of merit calculations a sample with 4 at.% In dopant concentration showed better optoelectronic properties.