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Title: Effect of thermal annealing on the redistribution of alkali metals in Cu(In,Ga)Se2 solar cells on glass substrate

Journal Article · · Journal of Applied Physics
DOI:https://doi.org/10.1063/1.5016949· OSTI ID:1429975
ORCiD logo [1];  [1]; ORCiD logo [1];  [1];  [2];  [1];  [1];  [1]
  1. National Inst. of Advanced Industrial Science and Technology (AIST), Tsukuba (Japan)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
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The precise control of alkali-metal concentrations in Cu(In,Ga)Se2 (CIGS) solar cells via post deposition treatment (PDT) has recently attracted attention. When PDT is performed at an elevated temperature, an accompanying annealing effect is expected. Here, we investigate how thermal annealing affects the redistribution of alkali metals in CIGS solar cells on glass substrates and the properties of the solar cells. In addition, we investigate the origin of non-homogeneous alkali-metal depth profiles that are typical of CIGS grown using a three-stage process. In particular, we use secondary-ion mass spectrometry measurements of the ion concentration as a function of distance from the CIGS surface to investigate the impact of thermal annealing on the distribution of alkali metals (Na, Ka, and Rb) and constituent elements (Ga and In) in the CIGS absorbers. We find that the depth profiles of the alkali metals strongly reflect the density of sites that tend to accommodate alkali metals, i.e., vacancies. Annealing at elevated temperature caused a redistribution of the alkali metals. The thermal-diffusion kinetics of alkali metals depends strongly on the species involved. We introduced low flux potassium fluoride (KF) to study a side effect of KF-PDT, i.e., Na removal from CIGS, separately from its predominant effects such as surface modification. When sufficient amounts of Na are supplied from the soda lime glass via annealing at an elevated temperature, the negative effect was not apparent. Conversely, when the Na supply was not sufficient, it caused a deterioration of the photovoltaic properties.

Research Organization:
National Renewable Energy Laboratory (NREL), Golden, CO (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Grant/Contract Number:
AC36-08GO28308
OSTI ID:
1429975
Report Number(s):
NREL/JA-5K00-71194; TRN: US1802487
Journal Information:
Journal of Applied Physics, Vol. 123, Issue 9; ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 11 works
Citation information provided by
Web of Science

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Cited By (1)

Role of surface microstructure of Mo back contact on alkali atom diffusion and Ga grading in Cu(In,Ga)Se 2 thin film solar cells journal April 2019

Figures / Tables (10)

Table I(p. 17)table Table I
Figure 1(p. 23)figure Figure 1
Figure 2(p. 24)figure Figure 2
Figure 3(p. 25)figure Figure 3
Figure 4(p. 26)figure Figure 4
Figure 5(p. 27)figure Figure 5
Figure 6(p. 28)figure Figure 6
Figure 7(p. 29)figure Figure 7
Figure 8(p. 30)figure Figure 8
Figure 9(p. 31)figure Figure 9

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