Characterization of Aluminum Doped Zinc Oxide (Azo) Thin Films Prepared by Reactive Thermal Evaporation for Solar Cell Applications
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Date
2015
Authors
Mugwang’a, F. K.
Karimi, P. K.
Njoroge, W. K.
Omayio, O.
Journal Title
Journal ISSN
Volume Title
Publisher
OMICS International
Abstract
Aluminium doped Zinc Oxide (AZO) thin films have been deposited using reactive thermal evaporation technique using an Edward
Auto 306 Magnetron Sputtering System. Transmittance and reflectance data in the range 300 nm-2500 nm were obtained using UV-VIS
NIR Spectrophotometer Solid State 3700 DUV for all the thin films samples that were prepared. Transmittance values of above 70%
were observed. The optical measurements were simulated using SCOUT 98 software to determine optical constants and optical bad
gap of the thin film. The optical properties in these films were varied by varying Aluminums doping percentages. It was observed that the
transmission over the visible range decreased as the concentration of Aluminum increased. This is due to free carriers coupling to the
electric field hence increasing the reflection. Optical band gap for various samples of Aluminum doped thin films show a direct allowed
transition and a shift in the optical absorption edge as the Aluminums concentration increased. These results show values of band gap
ranging between 3.2 eV and 3.5 eV. Between 0% - 3% the optical band gap reduces. This is followed with widening of the band gap
for doping between 4%- 6%. Urbach energy gradually increased with increasing band gap. The band gap reduced due to formation of
localized states near the conduction band corresponding to increase in Urbach energy
Description
Research Article
Keywords
Aluminums doped Zinc Oxide (AZO), Thin films, Optical properties, Reactive thermal evaporation technique, Solar cell applications
Citation
J Fundam Renewable Energy Appl Volume 5 Issue 4, 2015