Anti-reductive properties of AZO/FTO bilayered transparent conducting films

Abstract

Aluminium-doped zinc oxide (AZO)/fluorine-doped tin dioxide (FTO) double-layered transparent conducting films were manufactured on quartz glass substrates by spray pyrolysis. Like top films, AZO has marvellous reduction-resistant properties during a-Si:H deposition. However, as thin films with features of self-textured surfaces, SnO₂:F (FTO) provides high light scattering for front electrode in photovoltaic devices. The distribution of elements in surface and interface has been analysed by glow discharge spectrometer. The anti-reductive behaviour in ambient hydrogen plasma condition was studied and the results showed that hydrogen ions are dispersed in the AZO layer but not diffused to the FTO layer, thus avoiding the reduction of SnO₂ to SnO or Sn during hydrogen plasma bombardment. Besides, this phenomenon also indicated that the coating of the AZO layer on FTO electrode can increase the resistance of FTO to hydrogen. AZO film protects FTO from reduction, and the resistivity to hydrogen plasma of AZO/FTO bilayer films has been improved.