Effect of Sodium on the Properties of Ag(In, Ga)Se2 Thin Films and Solar Cells

Xianfeng Zhang; Masakazu Kobayashi

doi:10.1109/JPHOTOV.2017.2718588

Effect of Sodium on the Properties of Ag(In, Ga)Se₂ Thin Films and Solar Cells

Xianfeng Zhang^*, Masakazu Kobayashi

^*Corresponding author for this work

School of Advanced Science and Engineering

Research output: Contribution to journal › Article › peer-review

2 Citations (Scopus)

Abstract

Ag(In, Ga)Se₂ (AIGS) thin films were deposited by a modified three-stage method, using a molecular beam epitaxy apparatus. The influence of sodium on the properties of AIGS films was investigated, using Mo-coated soda-lime-glass (SLG) and quartz as substrates. A sodium concentration gradient was observed along the thickness direction of the AIGS film. This resulted from sodium diffusion from the SLG substrate. No sodium was observed in the AIGS film fabricated on the quartz substrate. The grain size and crystallinity of AIGS increased upon sodium doping. Photoluminescence (PL) experiments on the AIGS film showed that exponentially tailed donor states introduced by indium atoms were passivated by sodium. This led to free excitons being observed in the PL spectrum. Potential fluctuation was used to explain the emission spectra of both sodium-containing and sodium-free samples. The donor and acceptor levels included in the quasi-donor-acceptor pair recombination were observed at approximately 35 meV interstitial defect (GaAg) and 100 meV (V_Se), respectively. Solar cell performance was significantly improved by sodium doping, probably because of defect passivation.

Original language	English
Article number	7997696
Pages (from-to)	1426-1432
Number of pages	7
Journal	IEEE Journal of Photovoltaics
Volume	7
Issue number	5
DOIs	https://doi.org/10.1109/JPHOTOV.2017.2718588
Publication status	Published - 2017 Sept

Keywords

Ag(In
Ga)Se (AIGS)
photoluminescence
sodium doping

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Condensed Matter Physics
Electrical and Electronic Engineering

Access to Document

10.1109/JPHOTOV.2017.2718588

Cite this

@article{cea2d832951a44c18937d50f48b53182,

title = "Effect of Sodium on the Properties of Ag(In, Ga)Se2 Thin Films and Solar Cells",

abstract = "Ag(In, Ga)Se2 (AIGS) thin films were deposited by a modified three-stage method, using a molecular beam epitaxy apparatus. The influence of sodium on the properties of AIGS films was investigated, using Mo-coated soda-lime-glass (SLG) and quartz as substrates. A sodium concentration gradient was observed along the thickness direction of the AIGS film. This resulted from sodium diffusion from the SLG substrate. No sodium was observed in the AIGS film fabricated on the quartz substrate. The grain size and crystallinity of AIGS increased upon sodium doping. Photoluminescence (PL) experiments on the AIGS film showed that exponentially tailed donor states introduced by indium atoms were passivated by sodium. This led to free excitons being observed in the PL spectrum. Potential fluctuation was used to explain the emission spectra of both sodium-containing and sodium-free samples. The donor and acceptor levels included in the quasi-donor-acceptor pair recombination were observed at approximately 35 meV interstitial defect (GaAg) and 100 meV (VSe), respectively. Solar cell performance was significantly improved by sodium doping, probably because of defect passivation.",

keywords = "Ag(In, Ga)Se (AIGS), photoluminescence, sodium doping",

author = "Xianfeng Zhang and Masakazu Kobayashi",

note = "Funding Information: Manuscript received April 14, 2017; revised June 7, 2017; accepted June 9, 2017. Date of publication July 31, 2017; date of current version August 18, 2017. This work was supported in part by the New Energy and Industrial Technology Development Organization, Japan, in part by the Waseda University Initiatives, and in part by a Waseda University Grant for Special Research Projects (Corresponding author: Xianfeng Zhang.) X. Zhang is with the International Center for Science and Engineering Programs, Waseda University, Tokyo 169-8555, Japan (e-mail: zhangxf@aoni. waseda.jp). Publisher Copyright: {\textcopyright} 2011-2012 IEEE.",

year = "2017",

month = sep,

doi = "10.1109/JPHOTOV.2017.2718588",

language = "English",

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AU - Zhang, Xianfeng

AU - Kobayashi, Masakazu

N1 - Funding Information: Manuscript received April 14, 2017; revised June 7, 2017; accepted June 9, 2017. Date of publication July 31, 2017; date of current version August 18, 2017. This work was supported in part by the New Energy and Industrial Technology Development Organization, Japan, in part by the Waseda University Initiatives, and in part by a Waseda University Grant for Special Research Projects (Corresponding author: Xianfeng Zhang.) X. Zhang is with the International Center for Science and Engineering Programs, Waseda University, Tokyo 169-8555, Japan (e-mail: zhangxf@aoni. waseda.jp). Publisher Copyright: © 2011-2012 IEEE.

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N2 - Ag(In, Ga)Se2 (AIGS) thin films were deposited by a modified three-stage method, using a molecular beam epitaxy apparatus. The influence of sodium on the properties of AIGS films was investigated, using Mo-coated soda-lime-glass (SLG) and quartz as substrates. A sodium concentration gradient was observed along the thickness direction of the AIGS film. This resulted from sodium diffusion from the SLG substrate. No sodium was observed in the AIGS film fabricated on the quartz substrate. The grain size and crystallinity of AIGS increased upon sodium doping. Photoluminescence (PL) experiments on the AIGS film showed that exponentially tailed donor states introduced by indium atoms were passivated by sodium. This led to free excitons being observed in the PL spectrum. Potential fluctuation was used to explain the emission spectra of both sodium-containing and sodium-free samples. The donor and acceptor levels included in the quasi-donor-acceptor pair recombination were observed at approximately 35 meV interstitial defect (GaAg) and 100 meV (VSe), respectively. Solar cell performance was significantly improved by sodium doping, probably because of defect passivation.

AB - Ag(In, Ga)Se2 (AIGS) thin films were deposited by a modified three-stage method, using a molecular beam epitaxy apparatus. The influence of sodium on the properties of AIGS films was investigated, using Mo-coated soda-lime-glass (SLG) and quartz as substrates. A sodium concentration gradient was observed along the thickness direction of the AIGS film. This resulted from sodium diffusion from the SLG substrate. No sodium was observed in the AIGS film fabricated on the quartz substrate. The grain size and crystallinity of AIGS increased upon sodium doping. Photoluminescence (PL) experiments on the AIGS film showed that exponentially tailed donor states introduced by indium atoms were passivated by sodium. This led to free excitons being observed in the PL spectrum. Potential fluctuation was used to explain the emission spectra of both sodium-containing and sodium-free samples. The donor and acceptor levels included in the quasi-donor-acceptor pair recombination were observed at approximately 35 meV interstitial defect (GaAg) and 100 meV (VSe), respectively. Solar cell performance was significantly improved by sodium doping, probably because of defect passivation.

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