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Title: Combinatorial sputtering of Ga-doped (Zn,Mg)O for contact applications in solar cells

Abstract

In this study, the development of tunable contact materials based on environmentally friendly chemical elements using scalable deposition approaches is necessary for existing and emerging solar energy conversion technologies. In this paper, the properties of ZnO alloyed with magnesium (Mg), and doped with gallium (Ga) are studied using combinatorial thin film experiments. As a result of these studies, the optical band gap of the sputtered Zn 1-xMg xO thin films was determined to vary from 3.3 to 3.6 eV for a compositional spread of Mg content in the 0.04 < x < 0.17 range. Depending on whether or not Ga dopants were added, the electron concentrations were on the order of 10 17 cm -3 or 10 20 cm -3, respectively. Based on these results and on the Kelvin Probe work function measurements, a band diagram was derived using basic semiconductor physics equations. The quantitative determination of how the energy levels of Ga-doped (Zn, Mg)O thin films change as a function of Mg composition presented here, will facilitate their use as optimized contact layers for both Cu 2ZnSnS 4 (CZTS), Cu(In, Ga)Se 2 (CIGS) and other solar cell absorbers.

Authors:
 [1];  [2];  [2];  [3];  [2]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States); State Univ. of New York at Binghamton, Binghamton, NY (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  3. State Univ. of New York at Binghamton, Binghamton, NY (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
OSTI Identifier:
1326897
Report Number(s):
NREL/JA-5K00-66843
Journal ID: ISSN 0927-0248
Grant/Contract Number:
AC36-08GO28308
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Solar Energy Materials and Solar Cells
Additional Journal Information:
Journal Volume: 159; Journal Issue: C; Journal ID: ISSN 0927-0248
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; transparent conductive oxide; electron affinity; high-throughput experiments; electrical contact; photovoltaic; photo-electrochemical

Citation Formats

Rajbhandari, Pravakar P., Bikowski, Andre, Perkins, John D., Dhakal, Tara P., and Zakutayev, Andriy. Combinatorial sputtering of Ga-doped (Zn,Mg)O for contact applications in solar cells. United States: N. p., 2016. Web. doi:10.1016/j.solmat.2016.09.003.
Rajbhandari, Pravakar P., Bikowski, Andre, Perkins, John D., Dhakal, Tara P., & Zakutayev, Andriy. Combinatorial sputtering of Ga-doped (Zn,Mg)O for contact applications in solar cells. United States. doi:10.1016/j.solmat.2016.09.003.
Rajbhandari, Pravakar P., Bikowski, Andre, Perkins, John D., Dhakal, Tara P., and Zakutayev, Andriy. 2016. "Combinatorial sputtering of Ga-doped (Zn,Mg)O for contact applications in solar cells". United States. doi:10.1016/j.solmat.2016.09.003. https://www.osti.gov/servlets/purl/1326897.
@article{osti_1326897,
title = {Combinatorial sputtering of Ga-doped (Zn,Mg)O for contact applications in solar cells},
author = {Rajbhandari, Pravakar P. and Bikowski, Andre and Perkins, John D. and Dhakal, Tara P. and Zakutayev, Andriy},
abstractNote = {In this study, the development of tunable contact materials based on environmentally friendly chemical elements using scalable deposition approaches is necessary for existing and emerging solar energy conversion technologies. In this paper, the properties of ZnO alloyed with magnesium (Mg), and doped with gallium (Ga) are studied using combinatorial thin film experiments. As a result of these studies, the optical band gap of the sputtered Zn1-xMgxO thin films was determined to vary from 3.3 to 3.6 eV for a compositional spread of Mg content in the 0.04 < x < 0.17 range. Depending on whether or not Ga dopants were added, the electron concentrations were on the order of 1017 cm-3 or 1020 cm-3, respectively. Based on these results and on the Kelvin Probe work function measurements, a band diagram was derived using basic semiconductor physics equations. The quantitative determination of how the energy levels of Ga-doped (Zn, Mg)O thin films change as a function of Mg composition presented here, will facilitate their use as optimized contact layers for both Cu2ZnSnS4 (CZTS), Cu(In, Ga)Se2 (CIGS) and other solar cell absorbers.},
doi = {10.1016/j.solmat.2016.09.003},
journal = {Solar Energy Materials and Solar Cells},
number = C,
volume = 159,
place = {United States},
year = 2016,
month = 9
}

Journal Article:
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Cited by: 2works
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  • High-throughput computational and experimental techniques have been used in the past to accelerate the discovery of new promising solar cell materials. An important part of the development of novel thin film solar cell technologies, that is still considered a bottleneck for both theory and experiment, is the search for alternative interfacial contact (buffer) layers. The research and development of contact materials is difficult due to the inherent complexity that arises from its interactions at the interface with the absorber. A promising alternative to the commonly used CdS buffer layer in thin film solar cells that contain absorbers with lower electronmore » affinity can be found in ..beta..-In2S3. However, the synthesis conditions for the sputter deposition of this material are not well-established. Here, In2S3 is investigated as a solar cell contact material utilizing a high-throughput combinatorial screening of the temperature-flux parameter space, followed by a number of spatially resolved characterization techniques. It is demonstrated that, by tuning the sulfur partial pressure, phase pure ..beta..-In2S3 could be deposited using a broad range of substrate temperatures between 500 degrees C and ambient temperature. Combinatorial photovoltaic device libraries with Al/ZnO/In2S3/Cu2ZnSnS4/Mo/SiO2 structure were built at optimal processing conditions to investigate the feasibility of the sputtered In2S3 buffer layers and of an accelerated optimization of the device structure. The performance of the resulting In2S3/Cu2ZnSnS4 photovoltaic devices is on par with CdS/Cu2ZnSnS4 reference solar cells with similar values for short circuit currents and open circuit voltages, despite the overall quite low efficiency of the devices (-2%). Overall, these results demonstrate how a high-throughput experimental approach can be used to accelerate the development of contact materials and facilitate the optimization of thin film solar cell devices.« less
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