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Optical properties of ZnO/Al/ZnO multilayer films for large area transparent electrodes

Published online by Cambridge University Press:  17 November 2014

Egidius Rutatizibwa Rwenyagila ,
Benjamin Agyei-Tuffour ,
Martiale Gaetan Zebaze Kana ,
Omololu Akin-Ojo  and
Winston Oluwole Soboyejo
Egidius Rutatizibwa Rwenyagila
Affiliation:
Department of Materials Science and Engineering, African University of Science and Technology (AUST), PMB 681, Garki, Abuja, Nigeria; and Physics Department, University of Dar es Salaam, Dar es Salaam 35063, Tanzania
Benjamin Agyei-Tuffour
Affiliation:
Department of Materials Science and Engineering, African University of Science and Technology (AUST), PMB 681, Garki, Abuja, Nigeria
Martiale Gaetan Zebaze Kana
Affiliation:
Physics Advanced Laboratory, Sheda Science and Technology Complex (SHESTCO), Abuja, Nigeria; and Department of Materials Science and Engineering, Kwara State University, PMB 1531, Malete, Nigeria
Omololu Akin-Ojo
Affiliation:
Department of Theoretical and Applied Physics, African University of Science and Technology (AUST), PMB 681, Garki, Abuja, Nigeria
Winston Oluwole Soboyejo*
Affiliation:
Department of Materials Science and Engineering, African University of Science and Technology (AUST), PMB 681, Garki, Abuja, Nigeria; and Department of Mechanical and Aerospace Engineering & the Princeton Institute of Science and Technology of Materials, Princeton University, New Jersey 08544, USA
*
a)Address all correspondence to this author. e-mail: soboyejo@aol.com
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Abstract

This study presents the optical properties of layered ZnO/Al/ZnO composite thin films that are being explored for potential applications in solar cells and light emitting devices. The composite thin films are explored as alternatives to ZnO thin films. They are produced via radio frequency magnetron sputtering. The study clarifies the role of the aluminum mid-layer in a ZnO (25 nm)/Al/ZnO (25 nm) film structure. Multilayers with low resistivity ∼362 µΩ cm and average transmittances between ∼85 and 90% (in the visible region of the solar spectrum) are produced. The highest Haacke figure of merit of 4.72 × 10−3 Ω−1 was obtained in a multilayer with mid-layer Al thickness of 8 nm. The combined optical band gap energy of the multilayered films increased by ∼0.60 eV for mid-layer Al thicknesses between ∼1 and 10 nm. The observed shifts in the optical absorption edges to shorter wave lengths of the spectrum are shown to be in agreement with the Moss–Burstein effect.

Keywords

conductivitymid-Almultilayertransmittance
Type
Articles
Information
Journal of Materials Research , Volume 29 , Issue 24 , 28 December 2014 , pp. 2912 - 2920
Copyright
Copyright © Materials Research Society 2014 

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