Tailoring the structural, optoelectrical, and optical properties of the Al-doped ZnSnO3 thin films

In the current research, undoped and Al-doped ZnSnO₃ thin films are fabricated by cost-effective spray pyrolysis at various Al ratios. The XRD measurements reveal a rhombohedral structure for the ZnSnO₃ and Al-doped ZnSnO₃ thin films. The reflectance, R, and transmittance, T measurements of the ZnSnO₃ and Al-doped ZnSnO₃ thin films were employed to evaluate the linear optical parameters like refractive index, energy gap, and absorption coefficient. The increase in Al content improves the refractive index values and reduces the energy gap from 3.46 to 2.93 eV. The nonlinear absorption coefficient and nonlinear refractive index of the ZnSnO₃ and Al-doped ZnSnO₃ thin films were improved by raising the Al content from 2.5 to 7.5 wt%. The optoelectrical measurements show a significant increase in carrier concentration and electrical conductivity with increasing Al content, while optical analysis demonstrates a maintained or improved transparency in the visible range. These results suggest that the Al-doped ZnSnO₃ films offer high conductivity and excellent optical transparency, which are crucial for transparent conductive oxide (TCO) applications. On the other hand, the rise in Al content reduces the sheet resistance of the examined ZnSnO₃ and Al-doped ZnSnO₃ thin films. The figure of merit of the ZnSnO₃ and Al-doped ZnSnO₃ thin films was increased by raising the Al content from 2.5 to 7.5 wt%. The optimized Al doping concentration for achieving the best balance between conductivity and transparency is discussed, and the potential of Al-doped ZTO as a competitive TCO material for next-generation photovoltaic and electronic devices is highlighted.