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Open AccessFeature PaperArticle

Spectroscopic Ellipsometry Studies of n-i-p Hydrogenated Amorphous Silicon Based Photovoltaic Devices

Wright Center for Photovoltaics Innovation & Commercialization and Department of Physics & Astronomy, University of Toledo, Toledo, OH 43606, USA
Author to whom correspondence should be addressed.
Academic Editor: Joshua M. Pearce
Materials 2016, 9(3), 128;
Received: 1 January 2016 / Revised: 12 February 2016 / Accepted: 18 February 2016 / Published: 25 February 2016
(This article belongs to the Special Issue Photovoltaic Materials and Electronic Devices)
Optimization of thin film photovoltaics (PV) relies on characterizing the optoelectronic and structural properties of each layer and correlating these properties with device performance. Growth evolution diagrams have been used to guide production of materials with good optoelectronic properties in the full hydrogenated amorphous silicon (a-Si:H) PV device configuration. The nucleation and evolution of crystallites forming from the amorphous phase were studied using in situ near-infrared to ultraviolet spectroscopic ellipsometry during growth of films prepared as a function of hydrogen to reactive gas flow ratio R = [H2]/[SiH4]. In conjunction with higher photon energy measurements, the presence and relative absorption strength of silicon-hydrogen infrared modes were measured by infrared extended ellipsometry measurements to gain insight into chemical bonding. Structural and optical models have been developed for the back reflector (BR) structure consisting of sputtered undoped zinc oxide (ZnO) on top of silver (Ag) coated glass substrates. Characterization of the free-carrier absorption properties in Ag and the ZnO + Ag interface as well as phonon modes in ZnO were also studied by spectroscopic ellipsometry. Measurements ranging from 0.04 to 5 eV were used to extract layer thicknesses, composition, and optical response in the form of complex dielectric function spectra (ε = ε1 + iε2) for Ag, ZnO, the ZnO + Ag interface, and undoped a-Si:H layer in a substrate n-i-p a-Si:H based PV device structure. View Full-Text
Keywords: spectroscopic ellipsometry; hydrogenated silicon; infrared spectra; photovoltaic devices spectroscopic ellipsometry; hydrogenated silicon; infrared spectra; photovoltaic devices
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MDPI and ACS Style

Karki Gautam, L.; Junda, M.M.; Haneef, H.F.; Collins, R.W.; Podraza, N.J. Spectroscopic Ellipsometry Studies of n-i-p Hydrogenated Amorphous Silicon Based Photovoltaic Devices. Materials 2016, 9, 128.

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