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Transcript of Mitsuru Imaizumi HTV-5 Spacecraft Power System, Kyusyu Inst. Tech. Dec. 11, 2015.
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Mitsuru ImaizumiHTV-5
Spacecraft Power System, Kyusyu Inst. Tech. Dec. 11, 2015
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2
1. Operation principle and fundamentals
2. Radiation damage and effects
3. Radiation degradation characteristics4-1. Single-junction solar cell4-2. Multi-junction solar cell
Contents
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3
1. Operation principle and fundamentals
2. Radiation damage and effects
3. Radiation degradation characteristics4-1. Single-junction solar cell4-2. Multi-junction solar cell
Contents
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High efficiency Si solar cell
Cell size:2×2 cm2
InGaP/GaAs/Ge triple-junction solar cell
Size: 40mm×60mm Size: 37mm×76mm
Bypass diode Inter-connector
Space Solar Cells
Buried bypass diodes
4
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Operation Principle
Eg
empty
filled with electrons
Electrons
Holes
Intrinsic N-type P-type
Energy band in semiconductor
5
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Operation Principle
n-typeEmitterLayer
DepletionLayer
p-typeBase Layer
BSFLayer
Ev
Ec
Eg
Eph (>Eg)
Hole
ElectronDiffusion
Drift
Excitation(Generation)
Absorptionv
WindowLayer
6
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Current in Solar Cell
VIph Id
I
+_
7
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Current-Voltage (I-V) characteristics
-60
-40
-20
0
20
40
60
-1 -0.5 0 0.5 1Voltage (V)
CurrentDensity
(mA/cm 2)
dark
Output Characteristics
(a) Under dark (b) Under light
-60
-40
-20
0
20
40
60
-1 -0.5 0 0.5 1Voltage (V)
CurrentDensity
(mA/cm 2)
light
Photo- generation current
8
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-60
-40
-20
0
20
40
60
-1 -0.5 0 0.5 1Voltage (V)
CurrentDensity
(mA/cm2)
darklightpower
Voc
Isc Pmax
phB
ITk
qVII
1exp0
0
lnII
qTk
V scBoc
phsc II
Output Characteristics
9
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I-V Curve (Solar Cell Output)
0
10
20
30
40
50
60
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7Voltage (V)
Cur
rent
Den
sity
(mA
/cm
2 ) Isc
Voc
Pmax (Im,Vm)
FF = ImVm / IscVoc
h = Pmax / Po
Output Performance Parameters
10
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0
5
10
15
20
0 0.5 1 1.5 2 2.5 3Voltage (V)
Cur
rent
Den
sity
(mA
/cm
2 )
Jsc=16.9mA/cm2
Voc=2.652VFF=0.816h=27.0%
I-V Characteristics of a 3J solar cell
Output Performance
11
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Spectral Response
Quantum Efficiency of a high efficiency Si solar cell
0
20
40
60
80
100
300 400 500 600 700 800 900 1000 1100 1200
Wavelength (nm)
Qua
ntum
Eff
icie
ncy
(%)
%100)()()(
in
photon
outelectron
NNQE
12
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Equivalent Circuit of Solar Cell
V
Rs
RshIph
VdId
Ish
= 0
= ∞n = 1
1exp0 Tk
qVIIIB
phsh
s
B
sdph R
IRVTnkIRVqIII
1exp0
I
13
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0
0.05
0.1
0.15
0.2
0.25
250 500 750 1000 1250 1500 1750 2000Wavelength (nm)
Spec
trum
Irra
dian
ce (m
W/n
m/c
m2 ) AM0
0
1
2
3
4
5
6
7
0.5 1 1.5 2 2.5 3 3.5 4Photon Energy: Eph (eV)
Num
ber o
f Pho
tons
(×10
14/e
V/c
m2 /s
)
AM0
Ideal Current Output of Solar Cell
14
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0
1
2
3
4
5
6
7
0.5 1 1.5 2 2.5 3 3.5 4Photon Energy: Eph (eV)
Num
ber o
f Pho
tons
(×10
14/e
V/c
m2 /s
)
AM0
0
1
2
3
4
5
6
7
8
9
0 0.5 1 1.5 2 2.5 3 3.5 4Photon Energy: Eph (eV)
Num
ber o
f Pho
tons
in E
>E p
h (×1
0 17
/cm
2 /s)
AM0
Ideal Current Output of Solar Cell
15
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0
1
2
3
4
5
6
7
8
9
0 0.5 1 1.5 2 2.5 3 3.5 4Photon Energy: Eph (eV)
Num
ber o
f Pho
tons
in E
>E p
h (×1
0 17
/cm
2 /s)
AM0
0
20
40
60
80
100
120
0 0.5 1 1.5 2 2.5 3 3.5 4Energy gap: Eg (eV)
Idea
l Sho
rt-C
ircui
t Cur
rent
(mA
/cm
2 )
AM0
Ideal Current Output of Solar Cell
16
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0
20
40
60
80
100
0.5 1 1.5 2 2.5 3 3.5 4Energy gap: Eg (eV)
Idea
l Sho
rt-C
ircu
it C
urre
nt (m
A/c
m2 )AM0
Ideal Current/Voltage Output of Solar Cell
17
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18
Sun Light Sun Light
0
1
2
3
4
5
6
7
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0Photon Energy (eV)
Inte
grat
ed P
hoto
n N
umbe
r(×
1017
/cm
2 /s)
AM0
0
1
2
3
4
5
6
7
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0Photon Energy (eV)
Inte
grat
ed P
hoto
n N
umbe
r(×
1017
/cm
2 /s)
AM0
Ideal Current/Voltage Output of Solar Cell
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Output current estimation
×0
20
40
60
80
100
300 600 900 1200 1500
Wavelength (nm)Q
uant
um E
ffic
ienc
y (%
)
0
1
2
3
4
5
6
250 500 750 1000 1250 1500 1750 2000
Wavelength (nm)
Num
ber
of P
hoto
ns (×
1014
/nm
/cm
2 /s)
AM0
dNQEI )()(q phph
Spectral Response
19
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20
1. Operation principle and fundamentals
2. Radiation damage and effects
3. Radiation degradation characteristics4-1. Single-junction solar cell4-2. Multi-junction solar cell
Contents
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Incident of high-energy particles (electrons/protons)
↓Elastic/non-elastic collision
with atoms↓
Formation of vacancy-interstitial (Flenkel) pairs
↓(Some defect reactions)
↓Generation of minority-carrier recombination center(s) and majority-
carrier trap(s)
N-region
ElectronHole
Light
Defect
High-energyparticles
P-region Loss
Radiation Damage in Solar Cell
21
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Operation Principle
n-typeEmitterLayer
DepletionLayer
p-typeBase Layer
BSFLayer
Ev
Ec
Eg
Eph (>Eg)
Hole
ElectronDiffusion
Drift
Excitation(Generation)
Absorptionv
WindowLayer
22
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Radiation Degradation
n-typeEmitterLayer
DepletionLayer
p-typeBase Layer
BSFLayer
Ec
Ev
Eg
Hole
ElectronDiffusion
Recombination
DefectState
WindowLayer
23Minority-carrier recombination
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Before irradiation
Majority-carrier reduction24
After irradiation
Holes
Electrons
Holes
DefectState
Radiation Degradation
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Equivalent Circuit of Solar Cell
V
Rs
RshIph
n
sh
s
B
sdph R
IRVTnkIRVqIII
1exp0
I
25
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少数キャリア寿命低下の影響
I
V
R s
R shI ph
= 0
= ∞
0
lnII
qTk
V scBoc
0
10
20
30
40
50
60
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7Voltage (V)
Cur
rent
Den
sity
(mA
/cm
2 )
7 μs
5 μs
3 μs
1 μs0.1 μs
0.01 μs
放射線による性能劣化
26
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I
V
R s
R shI ph
= 0
0
10
20
30
40
50
60
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7Voltage (V)
Cur
rent
Den
sity
(mA
/cm
2 )
∞ Ω
100 Ω
20 Ω
10 Ω
5 Ω
2 Ω
shBph R
VTk
qVIII
1exp0
Effect of shunt resistance decrease
27
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0
10
20
30
40
50
60
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7Voltage (V)
Cur
rent
Den
sity
(mA
/cm
2 )
0 Ω
0.2 Ω
0.5 Ω
1 Ω
2 Ω
5 Ω
I
V
R s
R shI ph = ∞
1exp0 Tk
IRqVIIIB
sph
Effect of series resistance increase
28
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Decrease in output power
Cell size:2×2 cm2
Output Performance Degradation
Degradation trend (Pmax)
0
10
20
30
40
50
60
70
80
10MeV Proton Fluence (cm-2)M
axim
um P
ower
(mW
) BOL
EOL
1015Initial 1010 1011 1012 1013 10140
50
100
150
200
0 100 200 300 400 500 600Voltage (mV)
Cur
rent
(mA
)
照射量 大
Irradiation
29
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Degradation trend of high-efficiency Si solar cell
Degradation Trend
0
100
200
300
400
500
600
10MeV-Proton Fluence (cm-2)
Val
ue
Isc(mA)Voc(mV)Pmax(mW)
1015Initial 1010 1011 1012 1013 1014
Size: 2cm×2cm
0
0.2
0.4
0.6
0.8
1
10MeV-Proton Fluence (cm-2)
Rem
aini
ng F
acto
r
IscVocPmaxFF
1015Initial 1010 1011 1012 1013 1014
(a) Absolute values (b) Remaining factors
30
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Introduction of minority carrier recombination centers Change in minority carrier diffusion length (L)
Introduction of majority carrier traps Change in majority carrier concentration (p)
Decrease in carrier concentration (p) Increase in resistivity (r) and depletion region width (W)
LKLLL
2
022
111
p p p RC 0
pqp r 1
qpV
W bi02
Radiation Damage in Solar Cell
31
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32
1. Operation principle and fundamentals
2. Radiation damage and effects
3. Radiation degradation characteristics4-1. Single-junction solar cell4-2. Multi-junction solar cell
Contents
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B doped p-Si (100) base10 Wcm (2×1015cm-3)
p+-Si back surface field
Ti/Pd/Ag contactAl back surface reflector
Ti/Pd/Ag contactsAR coating (TiO2/Al2O3)
P doped n+-Si emitter
x j = 0.15 m
50/100 m
Degradation of Single-junction Solar Cell
Structure of sample solar cell
33
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Degradation trend of high-efficiency Si solar cell (a) 10MeV protons (b) 1MeV electrons
0
0.2
0.4
0.6
0.8
1
Rem
aini
ng F
acto
r
Fluence (cm-2 )1011 1015101410131012
0
0.2
0.4
0.6
0.8
1
Rem
aini
ng F
acto
rFluence (cm-2 )
101710151014 1016 1018
Degradation of Single-junction Solar Cell
34
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Low fluence region:Gradual decrease
↓
Transition region:Anomalous increase
in Isc
↓
High fluence region:Drastic decrease/
Sudden death
0
0.2
0.4
0.6
0.8
1
10MeV Proton Fluence (cm-2 )
Rem
aini
ng F
acto
r
IscVocPmax
1011 1015101410131012
Degradation of Single-junction Solar Cell
35
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Short circuit current (Isc) is expressed by
First stage: Reduction of L leads to a decrease in Isc.
Second stage: Reduction of p leads to an increase in W and consequently an increase in Isc.
Third stage: Reduction of p leads to an increase in resistivity and consequently abrupt decrease in Isc.
I I I q R Ink TSC phS SC
B
0 1exp NDPph IIII
pNnP LILI ,
WID exp1
rSR
Anomalous Degradation Analysis
36
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0
0.2
0.4
0.6
0.8
1R
emai
ning
Fac
tor o
f Is
c
10-MeV Proton Fluence (cm-2 )
Model with Lchange(Conventional
model)
Model with L, Rb, and W change (Proposed model)
Model with L and Rb change
KL = 2× 10-7
RC = 50 cm-1
1011 1015101410131012
Experimental Results
Anomalous Degradation Analysis
37
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0
0.2
0.4
0.6
0.8
1R
emai
ning
Fac
tor o
f Vo
c
10-MeV Proton Fluence (cm-2 )
Vnk Tq
IIOC
B SC
ln
0
1
Conventional model
Proposed model
1011 1015101410131012
Experimental Results
KL = 2×10-7
RC = 50 cm-1
Anomalous Degradation Analysis
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0
0.2
0.4
0.6
0.8
1R
emai
ning
Fac
tor o
f Pm
ax
10-MeV Proton Fluence (cm-2 )
1011 1015101410131012
P FF I VSC OCmax
Proposed model
Conventional model
Experimental Results
KL = 2×10-7
RC = 50 cm-1
Anomalous Degradation Analysis
39
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40
1. Operation principle and fundamentals
2. Radiation damage and effects
3. Radiation degradation characteristics4-1. Single-junction solar cell4-2. Multi-junction solar cell
Contents
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InGaP top cell
GaAs middle cell
Ge bottom cell(substrate)
~150mEg=0.7eV
~4mEg=1.4eV
Tunnel junction
N-electrode
P-electrode ARC
~0.5mEg=1.8eV
Structure of Space Solar Cell
InGaP/GaAs/Ge triple-junction solar cell
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Structure of 3J solar cells
Ge sub.
GaAs cellInGaP cell
3MeV Proton
TRIM simulation of 3MeV proton irradiation onto 3J solar cell
InGaP top cell
GaAs middle cell
Ge bottom cell(substrate)
Substrate140m
Epi layers~10m
P-electrode
N-electrode ARC
Degradation of Multi-junction Solar Cell
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0
0.2
0.4
0.6
0.8
1
0.01 0.1 1 10Proton Energy (MeV)
Rem
aini
ng F
acto
r
VocIscPmax
=1×1012 cm-2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1MeV Electron Fluence (cm-2)
Rem
aini
ng F
acto
r
VocIscPmax
1015 1016 1017 10181013 1014
Degradation of Multi-junction Solar Cell
Degradation trend curves Energy dependence of remaining factors
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0.2
0.4
0.6
0.8
1
10MeV Proton Fluence (cm-2)
Rem
aini
ng F
acto
r of I
sc
InGaP TopInGaAs MiddleGe Bottom
1015Initial 1010 1011 1012 1013 10140.2
0.4
0.6
0.8
1
10MeV Proton Fluence (cm-2)R
emai
ning
Fac
tor o
f Voc
InGaP TopInGaAs MiddleGe Bottom
1015Initial 1010 1011 1012 1013 1014
Degradation of Sub-cells in 3J Solar Cell
Isc degradation Voc degradation
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0
20
40
60
80
100
200 600 1000 1400 1800Wavelength (nm)
EQ
E (%
)
Top cell Middle cell
Bottom cell
Radiation-hardening of 3J Solar Cells
Spectral response of 3J cell Estimation of Isc of sub-cells in irradiated 3J solar cells
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