HIGH-EFFICIENCY DILUTE NITRIDE MULTIJUNCTION SOLAR … · HIGH-EFFICIENCY DILUTE NITRIDE...
Transcript of HIGH-EFFICIENCY DILUTE NITRIDE MULTIJUNCTION SOLAR … · HIGH-EFFICIENCY DILUTE NITRIDE...
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HIGH-EFFICIENCY DILUTE NITRIDE MULTIJUNCTION SOLAR CELLS: INFLUENCE OF POINT DEFECTS ON THE DEVICE PERFORMANCE
Ville Polojärvi, Arto Aho, Antti Tukiainen, Marianna Raappana, Timo Aho,
Mircea Guina
Optoelectronics Research Centre, Tampere University of Technology
Tampere, FINLAND
e-mail: [email protected]
www.tut.fi/orc/semicon
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Outline
• General motivation
• Concept
• Main methods
• Results on defect studies
• Multi-junction solar cell performance
• Summary
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Motivation
• Space applications,
satellites
https://upload.wikimedia.org/wikipedia/commons/8/8d/GPS_Satellite_NASA_art-iif.jpg
• Concentrated
photovoltaics (CPV)
https://upload.wikimedia.org/wikipedia/commons/thumb/5/5e/Amonix7700.jpg/450px-Amonix7700.jpg
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Motivation: CPV
By SolarGIS © 2013 GeoModel Solar, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=33459572
http://newenergyandfuel.com/wp-content/uploads/2014/
02/Fresnel-Lens-Basic-Principle-450x505.jpg
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Concept
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Methods: MBE
6
https://commons.wikimedia.org/wiki/File:Molecular_Beam_Epitaxy.png
• Molecular beam epitaxy (MBE)
• Solid sources, RF Plasma source for nitrogen
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Methods: CV measurements
7
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Methods: DLT(F)S
8
S. Weiss and R. Kassing, "Deep Level Transient Fourier Spectroscopy
(DLTFS)—A technique for the analysis of deep level properties", Solid-
State Electronics, vol. 31, pp. 1733-1742, 1988.
D. Lang, "Deep‐level transient spectroscopy: A new method to
characterize traps in semiconductors", J. Appl. Phys., vol. 45, pp.
3023-3032, 1974.
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Influence of material fluxes
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V/III beam equivalent pressure(BEP) ratio varied
During the growth of the dilute nitride i-region:
Sample1 (S1): 6
Sample2 (S2): 7
Sample3 (S3): 9
GaIn0.1N0.03As i-region
V. Polojärvi et al. / Solar Energy Materials & Solar Cells 149 (2016) 213–220
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Background doping and
defects
10 V. Polojärvi et al. / Solar Energy Materials & Solar Cells 149 (2016) 213–220
Sample1 (S1): BEP=6, Sample2 (S2): BEP=7, Sample3 (S3): BEP=9
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Trap parameters
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V. Polojärvi et al. / Solar Energy Materials & Solar Cells 149 (2016) 213–220
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Influence on solar cell
performance
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V. Polojärvi et al. / Solar Energy Materials & Solar Cells 149 (2016) 213–220
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”Linear” dependency on V/III
BEP ratio
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V. Polojärvi et al. / Solar Energy Materials & Solar Cells 149 (2016) 213–220
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Origin of the defects
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• No evidence on dislocations or extended defects
• Background doping could be caused by N-VGa compelex
• Deep levels can not be identified
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Influence of Sb composition
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Ville Polojärvi et al., Appl. Phys. Lett. 108, 122104 (2016)
Dilute nitride i-region, material composition
varied:
S1: GaIn0.11N0.04As
S2: GaN0.025AsSb0.06
S3: GaIn0.05N0.03AsSb0.03
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Background doping and
defects
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Ville Polojärvi et al., Appl. Phys. Lett. 108, 122104 (2016)
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Trap parameters
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S1: GaIn0.11N0.04As
S2: GaN0.025AsSb0.06
S3: GaIn0.05N0.03AsSb0.03
Ville Polojärvi et al., Appl. Phys. Lett. 108, 122104 (2016)
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Influence of thermal annealing
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S2: GaN0.025AsSb0.06
Ville Polojärvi et al., Appl. Phys. Lett. 108, 122104 (2016)
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GaInNAs vs GaInNAsSb in
GaInP/GaAs/dilute nitride
multijunction solar cell
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0.0 0.5 1.0 1.5 2.0 2.5 3.00
2
4
6
8
10
12
14
GaInP/GaAs/GaInNAs(Sb)
solar cells, bottom junction:
GaInNAs, =22 %
GaInNAsSb, =31 %
GaInNAsSb, 70 suns,
=37-39 %
Concentr
ation n
orm
alized
curr
ent
density(m
A/c
m2)
Voltage (V)
AM1.5
900 1000 1100 1200 13000.0
0.2
0.4
0.6
0.8
1.0
EQ
E
(nm)
GaInNAsSb bottom junction
GaInNAs bottom junction
LIV characteristics of 3-junction solar cells with dilute
nitride bottom junctions.
3-junction solar cells including dilute nitride bottom
junctions with and without Sb.
fill factor that increases from 80% to 90% when
the bottom junction is no longer limiting the
current
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SoA GaInNAsSb solar cells at ORC
Arto Aho et al.: proceedings CPV-11, April 2015, France
300 450 600 750 900 1050 1200 13500.0
0.2
0.4
0.6
0.8
1.0
GaInNAsSbGaAs
Jsc =
13.3
mA
/cm
2
Jsc =
16.0
mA
/cm
2
EQ
E
Wavelength (nm)
GaInP
Jsc =
13.6
mA
/cm
2
AM1.5G
2008 2010 2012 2014 2016
4
6
8
10
12
14
16
18
20
90% EQE
Theoretical limit
for the 1 eV sub-cell
AM1.5GCurr
ent
density (
mA
/cm
2)
Development year
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Future plans
21
4+ junctions for ≥50% conversion efficiency
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Conclusions
22
• Defects influence remarkably on solar cell performance
background doping, depletion region width
nonradiative recombination, carrier lifetimes, diffusion lengths
• Defect density / properties is sensitive to fabrication parameters, materials
compositions, thermal annealing…
• With careful optimization, dilute nitride does not limit the current in
GaInP/GaAs/dilute nitride 3-junction solar cell
• Dilute nitride multijunction solar cells has potential to reach very high conversion
efficiencies under concentrated sunlight as well as at AM0 conditions when
accompanied with high quality top junctions
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THANK YOU!
23
Disclaimer: the view expressed herein can in
no way be taken to reflect the official opinion
of the European Space Agency.