## Dependencies Between poly-Si Composition and Solar Cell Performance of poly-Si/SiOx Passivating Contacts

2020
Dissertation
Published
##### Abstract
In this thesis, dependencies between incorporation of foreign elements in the poly-Si layer and solar cell performance of poly-Si/SiOx passivating contacts are explored. For both dopant polarities a difference in total and electrically active dopant concentrations is observed. If applied on the front side of a solar cell, poly-Si/SiOx contacts based on phosphorus doped poly-Si layers are rather limited by free carrier absorption and based on boron doped poly-Si layers are rather limited by detrimental strong dopant in-diffusion. Incorporation of the light elements oxygen, nitrogen and carbon widens the optical band gap and thus lowers parasitic absorption in the poly-Si layer at the expense of a higher resistivity. Both effects are mediated by a lower crystallinity compared to pure poly-Si layers without incorporated light elements. Therefore, the crystallinity was identified as key parameter for solar cell performance if applied on the front side of a solar cell. All investigated layer types yield an excellent passivation quality in terms of contact recombination current densities down to Jc = 2.3 fA/cm2 and selectivities up to S10 = 15.2. The maximum achievable efficiency for an application of the investigated layers in an actual solar cell is estimated to 24.2% for a phosphorus doped poly-Si layer on the rear side and a boron doped poly-SiOxNy layer on the front side with thicknesses of 100 nm. This limit may be increased by 2%abs if the layer thicknesses are reduced to 30 nm.
530 Physics
##### Keywords
photovoltaics, polycrystalline silicon, poly-Si, passivating contacts
##### Cite This
ISO 690STEFFENS, Jonathan, 2020. Dependencies Between poly-Si Composition and Solar Cell Performance of poly-Si/SiOx Passivating Contacts [Dissertation]. Konstanz: University of Konstanz
BibTex
@phdthesis{Steffens2020Depen-51641,
year={2020},
title={Dependencies Between poly-Si Composition and Solar Cell Performance of poly-Si/SiO<sub>x</sub> Passivating Contacts},
author={Steffens, Jonathan},
school={Universität Konstanz}
}

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<dcterms:abstract xml:lang="eng">In this thesis, dependencies between incorporation of foreign elements in the poly-Si layer and solar cell performance of poly-Si/SiO&lt;sub&gt;x&lt;/sub&gt; passivating contacts are explored. For both dopant polarities a difference in total and electrically active dopant concentrations is observed. If applied on the front side of a solar cell, poly-Si/SiO&lt;sub&gt;x&lt;/sub&gt; contacts based on phosphorus doped poly-Si layers are rather limited by free carrier absorption and based on boron doped poly-Si layers are rather limited by detrimental strong dopant in-diffusion. Incorporation of the light elements oxygen, nitrogen and carbon widens the optical band gap and thus lowers parasitic absorption in the poly-Si layer at the expense of a higher resistivity. Both effects are mediated by a lower crystallinity compared to pure poly-Si layers without incorporated light elements. Therefore, the crystallinity was identified as key parameter for solar cell performance if applied on the front side of a solar cell. All investigated layer types yield an excellent passivation quality in terms of contact recombination current densities down to J&lt;sub&gt;c&lt;/sub&gt; = 2.3 fA/cm&lt;sup&gt;2&lt;/sup&gt; and selectivities up to S&lt;sub&gt;10&lt;/sub&gt; = 15.2. The maximum achievable efficiency for an application of the investigated layers in an actual solar cell is estimated to 24.2% for a phosphorus doped poly-Si layer on the rear side and a boron doped poly-SiO&lt;sub&gt;x&lt;/sub&gt;N&lt;sub&gt;y&lt;/sub&gt; layer on the front side with thicknesses of 100 nm. This limit may be increased by 2%&lt;sub&gt;abs&lt;/sub&gt; if the layer thicknesses are reduced to 30 nm.</dcterms:abstract>
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