Properties of Al-doped zinc oxide and In-doped zinc oxide bilayer transparent conducting oxides for solar cell applications

Abstract

Novel aluminum and indium doped zinc oxide (ZnO) bilayer transparent conducting oxide thin films was fabricated by simple sol-gel spin coating method and post-annealed at 500 °C for an hour under nitrogen ambient for solar cell applications. The structural, electrical and optical properties of both the as-deposited and annealed bilayer thin films were characterized. X-ray diffraction studies show a hexagonal wurtzite-type structure of ZnO with (0 0 2) orientation, which enhanced with annealing. In atomic force microscopy studies, minimum surface roughness was attained for Al-doped ZnO (AZO)/In-doped ZnO (IZO) bilayer TCO film compared to IZO/AZO bilayer film. The AZO/IZO film sheet resistance improved to 0.057 M ohm/square after post-annealing, while the single layer AZO film sheet resistance degraded upon annealing in nitrogen atmosphere. All the films had an average transmittance in the visible region over 96%.