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
Outline
• General motivation
• Concept
• Main methods
• Results on defect studies
• Multi-junction solar cell performance
• Summary
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
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
Concept
Methods: MBE
6
https://commons.wikimedia.org/wiki/File:Molecular_Beam_Epitaxy.png
• Molecular beam epitaxy (MBE)
• Solid sources, RF Plasma source for nitrogen
Methods: CV measurements
7
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.
Influence of material fluxes
9
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
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
Trap parameters
11
V. Polojärvi et al. / Solar Energy Materials & Solar Cells 149 (2016) 213–220
Influence on solar cell
performance
12
V. Polojärvi et al. / Solar Energy Materials & Solar Cells 149 (2016) 213–220
”Linear” dependency on V/III
BEP ratio
13
V. Polojärvi et al. / Solar Energy Materials & Solar Cells 149 (2016) 213–220
Origin of the defects
14
• No evidence on dislocations or extended defects
• Background doping could be caused by N-VGa compelex
• Deep levels can not be identified
Influence of Sb composition
15
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
Background doping and
defects
16
Ville Polojärvi et al., Appl. Phys. Lett. 108, 122104 (2016)
Trap parameters
17
S1: GaIn0.11N0.04As
S2: GaN0.025AsSb0.06
S3: GaIn0.05N0.03AsSb0.03
Ville Polojärvi et al., Appl. Phys. Lett. 108, 122104 (2016)
Influence of thermal annealing
18
S2: GaN0.025AsSb0.06
Ville Polojärvi et al., Appl. Phys. Lett. 108, 122104 (2016)
GaInNAs vs GaInNAsSb in
GaInP/GaAs/dilute nitride
multijunction solar cell
19
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
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
Future plans
21
4+ junctions for ≥50% conversion efficiency
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
THANK YOU!
23
Disclaimer: the view expressed herein can in
no way be taken to reflect the official opinion
of the European Space Agency.