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Title: Degradation of Mg-doped zinc oxide buffer layers in thin film CdTe solar cells

Abstract

Cadmium Sulphide is the conventional n-type buffer layer used in thin film Cadmium Telluride solar cells. It is well known that Cadmium Sulphide causes optical losses and sulphur diffuses into the absorber during high temperature activation. Sputter-deposited Mg-doped ZnO (MZO) has been shown to be an attractive buffer layer for Cadmium Telluride solar cells due to its transparency and tuneable band gap. It is also stable to high temperature processing and avoids diffusion of elements into the cadmium telluride absorber during the cadmium chloride activation treatment. However, degradation is observed in solar cells incorporating MZO buffer layers. Analysis of the MZO film surface potential has revealed significant fluctuations in the thin film work function once the layer is exposed to the atmosphere following deposition. These fluctuations are attributed to the high reactivity to water vapour of the MgO contained in the MZO films. This has been analysed using X-ray Photoelectron Spectroscopy to determine corresponding changes in the surface chemistry. The Zinc Oxide component is relatively stable, but the analysis shows that MgO forms a Mg(OH)2 layer on the MZO surface which forms a secondary barrier at the MZO/CdTe interface and/or at the interface between MZO and the Fluorine-doped SnO2. Thismore » affects the Fill Factor and as a consequence it degrades the conversion efficiency.« less

Authors:
ORCiD logo [1];  [1];  [1];  [1];  [1]; ORCiD logo [2];  [2];  [2]
  1. Loughborough Univ., Loughborough, Leicestershire (United Kingdom)
  2. Colorado State Univ., Fort Collins, CO (United States)
Publication Date:
Research Org.:
Colorado State Univ., Fort Collins, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE); National Science Foundation (NSF)
OSTI Identifier:
1670786
Grant/Contract Number:  
EE0008557
Resource Type:
Accepted Manuscript
Journal Name:
Thin Solid Films
Additional Journal Information:
Journal Volume: 691; Journal ID: ISSN 0040-6090
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; Magnesium-doped zinc oxide; Thin film solar cells; Cadmium telluride; Buffer; Degradation; Hydroxide; Surface contamination

Citation Formats

Bittau, Francesco, Jagdale, Shridhar, Potamialis, Christos, Bowers, Jake W., Walls, John M., Munshi, Amit H., Barth, Kurt L., and Sampath, Walajabad S. Degradation of Mg-doped zinc oxide buffer layers in thin film CdTe solar cells. United States: N. p., 2019. Web. doi:10.1016/j.tsf.2019.137556.
Bittau, Francesco, Jagdale, Shridhar, Potamialis, Christos, Bowers, Jake W., Walls, John M., Munshi, Amit H., Barth, Kurt L., & Sampath, Walajabad S. Degradation of Mg-doped zinc oxide buffer layers in thin film CdTe solar cells. United States. https://doi.org/10.1016/j.tsf.2019.137556
Bittau, Francesco, Jagdale, Shridhar, Potamialis, Christos, Bowers, Jake W., Walls, John M., Munshi, Amit H., Barth, Kurt L., and Sampath, Walajabad S. Mon . "Degradation of Mg-doped zinc oxide buffer layers in thin film CdTe solar cells". United States. https://doi.org/10.1016/j.tsf.2019.137556. https://www.osti.gov/servlets/purl/1670786.
@article{osti_1670786,
title = {Degradation of Mg-doped zinc oxide buffer layers in thin film CdTe solar cells},
author = {Bittau, Francesco and Jagdale, Shridhar and Potamialis, Christos and Bowers, Jake W. and Walls, John M. and Munshi, Amit H. and Barth, Kurt L. and Sampath, Walajabad S.},
abstractNote = {Cadmium Sulphide is the conventional n-type buffer layer used in thin film Cadmium Telluride solar cells. It is well known that Cadmium Sulphide causes optical losses and sulphur diffuses into the absorber during high temperature activation. Sputter-deposited Mg-doped ZnO (MZO) has been shown to be an attractive buffer layer for Cadmium Telluride solar cells due to its transparency and tuneable band gap. It is also stable to high temperature processing and avoids diffusion of elements into the cadmium telluride absorber during the cadmium chloride activation treatment. However, degradation is observed in solar cells incorporating MZO buffer layers. Analysis of the MZO film surface potential has revealed significant fluctuations in the thin film work function once the layer is exposed to the atmosphere following deposition. These fluctuations are attributed to the high reactivity to water vapour of the MgO contained in the MZO films. This has been analysed using X-ray Photoelectron Spectroscopy to determine corresponding changes in the surface chemistry. The Zinc Oxide component is relatively stable, but the analysis shows that MgO forms a Mg(OH)2 layer on the MZO surface which forms a secondary barrier at the MZO/CdTe interface and/or at the interface between MZO and the Fluorine-doped SnO2. This affects the Fill Factor and as a consequence it degrades the conversion efficiency.},
doi = {10.1016/j.tsf.2019.137556},
journal = {Thin Solid Films},
number = ,
volume = 691,
place = {United States},
year = {Mon Sep 09 00:00:00 EDT 2019},
month = {Mon Sep 09 00:00:00 EDT 2019}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Figures / Tables:

Fig. 1 Fig. 1: Schematic diagram of the conventional structure of a thin film CdTe solar device. The use of CdS causes parasitic absorption losses which can be eliminated by using a wide band gap buffer layer such as magnesium doped zinc oxide (MZO).

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Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.