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, SnO 2 :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 SnO 2 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.

Solution processed glass/fluorine-doped tin oxide/aluminum-doped zinc oxide double layer thin films for transparent heater and near-infrared reflecting applications

“…Moreover, such an epitaxial growth for the AZO layer was not expected due to dynamic deposition conditions specific to USP method. Yu et al showed that AZO thin films produced by the USP method on 540 nm thick and polycrystalline FTO layers possess very similar XRD pattern compared to our sample [40]. Their AZO layer thicknesses were very thin i.e., 10-100 nm, compared to our AZO layer thickness.…”

“…The study has shown that the optoelectronic properties of as-deposited (2891 Ω/sq, 78% visible transmittance, 400 °C deposition temperature, glass substrate) thin films were not sufficient for THs applications without a post-deposition annealing step (38.7 Ω/sq, 83% visible transmittance, 400 °C annealing temperature, Ar + 4% H 2 , 90 min). On the other hand, USP-deposited FTO/ AZO double layer thin films were mostly examined for antireductive properties during a-Si:H deposition [40,41] and as a substitute for ITO in solar cell transparent electrodes [42] due to the higher durability of AZO to hydrogen environment at high temperatures [43]. In addition, Ravikumar et al investigated the effect of FTO layer thickness on the optoelectronic properties of AZO/FTO spray pyrolysis-deposited double layer films [44].…”

Oxygen effect on structural and optical properties of zinc oxide

“…ZnO is a well-transparent conductive oxide, which has a wide energy band gap of 3.37 eV, good electrical conductivity of 10 3 Ω −1 cm −1 , abundance, and environmentally friendly [1][2][3]. Because of its advantages, zinc oxide can be used in several applications like solar cells, optical and gas sensors, ultrasonic oscillators, transductors, transparent conductors and photoprotective coatings [4][5][6][7][8]. These applications depend on ZnO properties that are influenced by different factors like deposition conditions, chemical composition, ZnO structural, defects and preferential orientation.…”