Intersolar – SEMI Workshop
Munich, July 14th 2012
Limitation of solar cell
efficiency by oxygen
and metal impurities
22
21
Co
Efficiency [%]
20
19
Ni
Fe
Cu
Cr
K. Bothe
18
17
16
15
(a) p-Si base
14
1010
1011
1012
1013
1014
1015
-3
Metal impurity concentration [cm ]
Fei, Nt (cm-3) vs eta
CrB, Nt (cm-3) vs eta CrB
Ni, Nt (cm-3) vs eta Ni
Cu, Nt (cm-3) vs eta Cu
Co, Nt (cm-3) vs eta Co
Mn, Nt (cm-3) vs eta Mn
1016
Light-induced degradation
in mc-Si solar cells
16
Efficiency  [%]
15
14
13
12
rel [%]
11
10
1
2
3
4
5
6
initial state
after illumination
FeiBs
Dissociation
Ladungsträgerlebensdauer
 (µs)
Lifetime intsbility in mc-Si
under illumination
26
24
22
20
18
NFe=1.21012 cm-3
16
14
12
0
1
2
3
4
5
6
Ladungsträgerlebensdauer
 (µs)
Beleuchtungsdauer (min)
180
160
140
120
100
80
0
5
10
15
20
Beleuchtungsdauer (min)
BsO2i
Formation
-3
Interstitial oxygen concentration [Oi] [cm ]
Oxygen concentration in mc-Si
.
1018
.
Cz-Si
.
A edge
A center
B edge
B center
1017
top
bottom
0
20
40
60
80
Position towards top [%]
L.J. Geerligs, 12th NREL Workshop, 2002, p. 280
100
LIGHT-INDUCED DEGRADATION
Discovery of light-induced degradation
in the early 1970‘s
Fischer and Pschunder, Proc. 10th IEEE PVSC, 1973, p. 404
•
Cz-Si solar cells are more
resistive to electron irradiation
than FZ-Si solar cells
•
Degradation of solar cell
parameters of Cz-Si solar cells
under illumination (even before
electron irradiance)
•
Full recovery of initial
parameters by annealing at
~200°C
Formation of recombination-active
defect center under illumination
Fischer and Pschunder, Proc. 10th IEEE PVSC, 1973, p. 404
•
Activation of a metastable
recombination-active
defect center
•
Underlying physical
mechanism unclear
„Re-discovery“ of light induced
degradation in the mid 1990‘s
21.0
 Fundamental LID effect found in
B-doped Cz-Si made from electronicgrade feedstock
Efficiency (%)
20.5
20.0
AM 1.5
1 sun
19.5
 Complete recovery of initial values by
annealing at around 200°C for 10 min
200°C
19.0
 Degradation of energy conversion
efficiency by up to 10%rel
PERL cell on
1 cm B-doped Cz-Si
18.5
18.0
0
20
40
60
80
100 120
Illumination time (h)
J. Knobloch et al., 25th IEEE PVSC, 1996, p. 405 – Schmidt et al., 26th IEEE PVSC, 1997, p. 13
Injection-dependence of carrier
lifetime in B-doped Cz-Si
Effective Carrier Lifetime
eff
[µs]
B-doped Cz-Si
15
-3
Ndop=5.1 10 cm
2
10
deactivated
200°C 10min
fully activated
60h illumination
101
1012
1
1
1


 SRH  n   d  n   0  n 
298K
1013
1014
1015
1016
Excess Carrier Concentration n [cm-3]
1017
Lifetime Parameterisation
• More than 30 different
Cz-Si materials
Fundamental boron-oxygen-related carrier lifetime limit in mono- and multicrystalline silicon,
K. Bothe, R. Sinton, and J. Schmidt, Prog. Photovolt: Res. Appl. 13 (2005) p. 287
Lifetime Parameterisation
• More than 30 different
Cz-Si materials
• Oxygen content varying
between 2 and 101017 cm-3
Fundamental boron-oxygen-related carrier lifetime limit in mono- and multicrystalline silicon,
K. Bothe, R. Sinton, and J. Schmidt, Prog. Photovolt: Res. Appl. 13 (2005) p. 287
Lifetime Parameterisation
• More than 30 different
Cz-Si materials
• Oxygen content varying
between 2 and 101017 cm-3
• Boron content varying
between 0.1 and 101016 cm-3
Fundamental boron-oxygen-related carrier lifetime limit in mono- and multicrystalline silicon,
K. Bothe, R. Sinton, and J. Schmidt, Prog. Photovolt: Res. Appl. 13 (2005) p. 287
Lifetime Parameterisation
• Data points are given
as circles
• Distance between circles
and plane is indicated by
perpendicular lines
• Remarkable small deviation
between data points and
parameterisation
Boron and oxygen content
predicts carrier lifetime !
Fundamental boron-oxygen-related carrier lifetime limit in mono- and multicrystalline silicon,
K. Bothe, R. Sinton, and J. Schmidt, Prog. Photovolt: Res. Appl. 13 (2005) p. 287
Lifetime Parameterisation
• Data points are given
as circles
 d   eff  n  0.1 Ndop   7.675  10  [B ]
between circles
45 • Distance
0.824
1.748
ands plane is indicated
by
i
perpendicular lines
 [O ]
• Remarkable small deviation
between data points and
parameterisation
Boron and oxygen content
predicts carrier lifetime !
Fundamental boron-oxygen-related carrier lifetime limit in mono- and multicrystalline silicon,
K. Bothe, R. Sinton, and J. Schmidt, Prog. Photovolt: Res. Appl. 13 (2005) p. 287
PC1D input parameters
Parameterizaton for arbitrary
injection level 
110 
1
1
45
0.824
 SRH.BsO2i ( n, Ndop ) 

 [Oi ]1.748

  7.675  10  [Bs ]
21  Ndop n  1 10 
d
n 0
 n0 
 p0
n 
11
d
21
121

d
21
Parameterizaton for arbitrary
injection level 
110 
1
1
45
0.824
 SRH.BsO2i ( n, Ndop ) 

 [Oi ]1.748

  7.675  10  [Bs ]
21  Ndop n  1 10 
d
n 0
 n0 
 p0
n 
11
d
21
121

d
21
600
580
560
540
1015
[Oi]<2.5 1016cm-3
[Oi]=4.2 1017cm-3
[Oi]=8.2 1017cm-3
1016
1017
-3
Doping Concentration NA [cm ]
17
34
[%]
620
35
33
Efficiency
640
Short-circuit Current Density JSC [mA/cm2]
Open-circuit Voltage VOC [mV]
Impact of BsO2i on solar
cell performance – industrial
32
31
16
15
14
30
29
1015
1016
1017
-3
Doping Concentration NA [cm ]
13
1015
1016
1017
Doping Concentration NA [cm-3]
DEACTIVIATION OF
LIGHT-INDUCED DEGRADATION
Lifetime recovery under illumination
at elevated temperature
•
Lifetime in degraded samples
increases under illumination at
temperatures between 135 °C
and 215 °C
•
Speed of recovery increases with
increasing temperature
•
Faster recovery after P-diffusion
A. Herguth, G. Schubert, M. Kaes, and G. Hahn., Proc. 21st EUPVSEC,
Dresden, Germany, (Munich: WIP 2006 ), p.530
B. Lim, K. Bothe, and J. Schmidt, phys. stat. sol. (RRL) 2, 93 (2008)
Stabilized RISE-EWT solar cells
•
•
•
•
Illumination at ~100 mW/cm2 and
200°C for 1 hour
Complete recovery of  and VOC
to values before degradation
VOC and  are stable under illumination
at room temperature
20.3 % stabilized efficiency (92 cm2 a. a.)
•
•
•
Carrier lifetime cured after
permanent deactivation
Strong scatter even for similar
deactivation procedure and
sample properties
Parametrization of best values
yields:
 cured = 1026 NA-1.46
Lifetime @ n = 0.1 NA [ s]
Parameterization of cured
B-doped p-type Cz-Si
after phosphorus diffusion
after curing
26
1.46
cur = 10 NA
1000
100
after complete
degradation
14
deg = 8.72 10 NA
10
1015
0.824
1016
1017
Boron concentration NA [cm-3]
23
•
Carrier lifetime cured after
permanent deactivation (curing)
•
Strong scatter even for similar
deactivation procedure and
sample properties
•
Parametrization of best values
yields:
 cured = 1026 NA-1.46
PC1D
Lifetime @ n = 0.1 NA [ s]
Parameterization of cured
B-doped p-type Cz-Si
after phosphorus diffusion
after curing
26
1.46
cur = 10 NA
1000
100
after complete
degradation
14
deg = 8.72 10 NA
10
1015
0.824
1016
1017
Boron concentration NA [cm-3]
n0.cured = 5.251025 NA-1.46
p0.cured = 10n0.cured
24
cured
620
610
degraded
600
[Oi]<2.5 1016cm-3
[Oi]=4.2 1017cm-3
[Oi]=8.2 1017cm-3
590
580
1015
1016
1017
Doping Concentration NA [cm-3]
34
[%]
630
17
35
33
Efficiency
640
Short-circuit Current Density JSC [mA/cm2]
Open-circuit Voltage VOC [mV]
Impact of BsO2i on solar
cell performance – industrial
32
31
cured
16
degraded
15
30
29
1015
1016
1017
Doping Concentration NA [cm-3]
14
1015
1016
1017
Doping Concentration NA [cm-3]
IMPACT OF METAL IMPURITIES
ON CELL EFFICIENY
Typical impurity levels
Feedstock
Ingot / Wafer
Solar cell
liquid phase
solar grade 5N-6N
total
≤1015 cm-3
total
≤ 1015 cm-3
gas phase
electronic grade 9N-10N
[Fe]
≤ 1018 cm-3
8N = 99.999999% pure silicon = 1015 impurity atoms/cm3
electrically active
≤ 1013 cm-3
≤ 1013 cm-3
electrically active
≤ 1012 cm-3
≤ 1012 cm-3
Metal impurity content in Si wafers
T. Buonassisi et al., Prog. Photovolt: Res. Appl. 14 (2006) p. 513
Metal impurity content in Si wafers
fast diffusing (Cu, Fe, Cr, Ni)
slow diffusing (Mo, Ti)
T. Buonassisi et al., Prog. Photovolt: Res. Appl. 14 (2006) p. 513
Impact of metal impurities
• Experimental approach
 Westinghouse (J.R. Davis et al., IEEE Trans. Electron Devices ED-27 (1980) p. 677)
 CrystalClear (G. Coletti et al., Adv. Func. Mat. 21 (2011) p. 879)
 SolarFocus (S. Riepe et al., Phys. Stat. Sol. C 8 (2011) p. 733)
…
• Simulation approach
 Fe (PC1D) (J. Schmidt et al., Prog. Photovolt: Res. Appl. 13 (2005) p. 325)
 Fe, Cr, Au, Mo, Pt (PC1D) (H. Nagel et al., Proc. 20th EU-PVSEC 2005, p. 1271)
 Fe, Cr, Ni, Cu, Co (Sentaurus) (J. Schmidt et al., Proc. 38th IEEE-PVSC 2012)
…
Impact of metal impurities
• Experimental approach
  Westinghouse (J.R. Davis et al., IEEE Trans. Electron Devices ED-27 (1980) p. 677)
 CrystalClear (G. Coletti et al., Adv. Func. Mat. 21 (2011) p. 879)

   SolarFocus (S. Riepe et al., Phys. Stat. Sol. C 8 (2011) p. 733)
Feedstock
total
Ingot / Wafer
Solar cell
total
NAA, SSMS
total
electrically active
IDLS
electrically active
Impact of metal impurities
• Simulation approach




 Fe (PC1D) (J. Schmidt et al., Prog. Photovolt: Res. Appl. 13 (2005) p. 325)
 Fe, Cr, Au, Mo, Pt (PC1D) (H. Nagel et al., Proc. 20th EU-PVSEC 2005, p. 1271)
 Mo, Fe, Ti, Ni (PC1D) (S. Rein, Lifetime Spectroscopy, Springer 2005)
 Fe, Cr, Ni, Cu, Co (Sentaurus) (J. Schmidt et al., Proc. 38th IEEE-PVSC 2012)
…
Feedstock
total
Ingot / Wafer
Solar cell
total
NAA, SSMS
total
electrically active
IDLS
electrically active
Impact of metal impurities
• Experimental approach
 Westinghouse (J.R. Davis et al., IEEE Trans. Electron Devices ED-27 (1980) p. 677)
 CrystalClear (G. Coletti et al., Adv. Func. Mat. 21 (2011) p. 879)
 SolarFocus (S. Riepe et al., Phys. Stat. Sol. C 8 (2011) p. 733)
 200 Cz ingots grown
 Melt impurity around 1020 cm-3
 Baseline efficiency 14%
 Reduces diffusion length:
Ni, Cu, Fe, Nb, Ti, V, Ta, W,
Mo, Pd, Au, Zr, Mn, Al, Sn
 Degrades junction:
Ni, Cu, Fe
Total wafer concentration
Impact of metal impurities
• Experimental approach
 Westinghouse (J.R. Davis et al., IEEE Trans. Electron Devices ED-27 (1980) p. 677)
 CrystalClear (G. Coletti et al., Adv. Func. Mat. 21 (2011) p. 879)
 SolarFocus (S. Riepe et al., Phys. Stat. Sol. C 8 (2011) p. 733)
 200 Cz ingots grown
 Melt impurity <1020 cm-3
 Baseline efficiency 14%
 Reduces diffusion length:
Ni, Cu, Fe, Nb, Ti, V, Ta, W,
Mo, Pd, Au, Zr, Mn, Al, Sn
Nthres [cm-3]
Wafer
Fe
11014
Cr
11014
Cu
11017
Total wafer concentration
Impact of metal impurities
• Experimental approach
 Westinghouse (J.R. Davis et al., IEEE Trans. Electron Devices ED-27 (1980) p. 677)
 CrystalClear (G. Coletti et al., Adv. Func. Mat. 21 (2011) p. 879)
 SolarFocus (S. Riepe et al., Phys. Stat. Sol. C 8 (2011) p. 733)
 Aims at defining specifications for upper
impurity levels in solar grade feedstock
for mc-Si
 High impurities levels may result in poorer
cystallographic structure (Fe, Cr, Ni, Cu)
 Melt impurity <1020 cm-3
 Baseline efficiency 15%
 Reduces diffusion length:
Fe, Cu, Cr, Ti
 Degrades junction:
Ni
Impact of metal impurities
• Experimental approach
 Westinghouse (J.R. Davis et al., IEEE Trans. Electron Devices ED-27 (1980) p. 677)
 CrystalClear (G. Coletti et al., Adv. Func. Mat. 21 (2011) p. 879)
 SolarFocus (S. Riepe et al., Phys. Stat. Sol. C 8 (2011) p. 733)
 Aims at defining specifications for upper
impurity levels in solar grade feedstock
for mc-Si
 High impurities levels may result in poorer
cystallographic structure (Fe, Cr, Ni, Cu)
 Melt impurity <1020 cm-3
 Baseline efficiency 15%
 Reduces diffusion length:
Fe, Cu, Cr, Ti
 Degrades junction:
Nthres [cm-3] Feedstock
Ni
Fe
31017
Wafer
--
Cr
21017
--
Cu
21017
--
Impact of metal impurities
• Experimental approach
 Westinghouse (J.R. Davis et al., IEEE Trans. Electron Devices ED-27 (1980) p. 677)
 CrystalClear (G. Coletti et al., Adv. Func. Mat. 21 (2011) p. 879)
 SolarFocus (S. Riepe et al., Phys. Stat. Sol. C 8 (2011) p. 733)





In-diffusion fom crucible
Back-diffusion from top region
Baseline efficiency 16%
Strong precipitation behaviour for all metals
Preferred formation of shunts
Nthres [cm-3]
Feedstock
Wafer
Fe
11017
11014
Cr
0.61017
31012
Cu
0.91017
31014
Impact of metal impurities
• Experimental approach
 Westinghouse (J.R. Davis et al., IEEE Trans. Electron Devices ED-27 (1980) p. 677)
vs Fe
 CrystalClear (G. Coletti et Col
al., 1Adv.
Func. Mat. 21 (2011) p. 879)
Col
3
vs
Cr
 SolarFocus (S. Riepe et al., Phys. Stat. Sol. C 8 (2011) p. 733)
Col 5 vs Cu





In-diffusion fom crucible
Back-diffusion from top region
Baseline efficiency 16%
Strong precipitation behaviour for all metals
Fe
Cr
Preferred formation of shunts
Nthres [cm-3]
Feedstock
Wafer
Fe
11017
11014
Cr
0.61017
31012
Cu
0.91017
31014
Cu
Impact of metal impurities
• Simulation approach
 Fe (PC1D) (J. Schmidt et al., Prog. Photovolt: Res. Appl. 13 (2005) p. 325)
 Fe, Cr, Au, Mo, Pt (PC1D) (H. Nagel et al., Proc. 20th EU-PVSEC 2005, p. 1271)
 Mo, Fe, Ti, Ni (PC1D) (S. Rein, Lifetime Spectroscopy, Springer 2005)
 Fe, Cr, Ni, Cu, Co (Sentaurus) (J. Schmidt et al., Proc. 38th IEEE-PVSC 2012)
…
Impact of metal impurities
• Simulation approach
 Fe (PC1D) (J. Schmidt et al., Prog. Photovolt: Res. Appl. 13 (2005) p. 325)
 Fe, Cr, Au, Mo, Pt (PC1D) (H. Nagel et al., Proc. 20th EU-PVSEC 2005, p. 1271)
 Mo, Fe, Ti, Ni (PC1D) (S. Rein, Lifetime Spectroscopy, Springer 2005)
 Fe, Cr, Ni, Cu, Co (Sentaurus) (J. Schmidt et al., Proc. 38th IEEE-PVSC 2012)
…
Impact of metal impurities
• Simulation approach
 Fe (PC1D) (J. Schmidt et al., Prog. Photovolt: Res. Appl. 13 (2005) p. 325)
 Fe, Cr, Au, Mo, Pt (PC1D) (H. Nagel et al., Proc. 20th EU-PVSEC 2005, p. 1271)
 Mo, Fe, Ti, Ni (PC1D) (S. Rein, Lifetime Spectroscopy, Springer 2005)
 Fe, Cr, Ni, Cu, Co (Sentaurus) (J. Schmidt et al., Proc. 38th IEEE-PVSC 2012)
…
Nthres [cm-3]
Solar cell
(electrically active)
Fe
21010
Cr
2109
Impact of metal impurities
• Simulation approach
 Fe (PC1D) (J. Schmidt et al., Prog. Photovolt: Res. Appl. 13 (2005) p. 325)
 Fe, Cr, Au, Mo, Pt (PC1D) (H. Nagel et al., Proc. 20th EU-PVSEC 2005, p. 1271)
 Mo, Fe, Ti, Ni (PC1D) (S. Rein, Lifetime Spectroscopy, Springer 2005)
 Fe, Cr, Ni, Cu, Co (Sentaurus) (J. Schmidt et al., Proc. 38th IEEE-PVSC 2012)
…
Nthres [cm-3]
Solar cell
(electrically active)
Fe
21012
Impact of metal impurities
• Simulation approach
 Fe (PC1D) (J. Schmidt et al., Prog. Photovolt: Res. Appl. 13 (2005) p. 325)
 Fe, Cr, Au, Mo, Pt (PC1D) (H. Nagel et al., Proc. 20th EU-PVSEC 2005, p. 1271)
 Mo, Fe, Ti, Ni (PC1D) (S. Rein, Lifetime Spectroscopy, Springer 2005)
 Fe, Cr, Ni, Cu, Co (Sentaurus) (J. Schmidt et al., Proc. 38th IEEE-PVSC 2012)
…
Nthres [cm-3]
Solar cell
(electrically active)
Fe
21012
Impact of metal impurities
• Simulation approach
 Fe (PC1D) (J. Schmidt et al., Prog. Photovolt: Res. Appl. 13 (2005) p. 325)
 Fe, Cr, Au, Mo, Pt (PC1D) (H. Nagel et al., Proc. 20th EU-PVSEC 2005, p. 1271)
 Mo, Fe, Ti, Ni (PC1D) (S. Rein, Lifetime Spectroscopy, Springer 2005)
 Fe, Cr, Ni, Cu, Co (Sentaurus) (J. Schmidt et al., Proc. 38th IEEE-PVSC 2012)
…
Nthres [cm-3]
Solar cell
(electrically active)
Fe
21012
Author
sn.Fe [cm2]
sp-Fe [cm2]
Et [eV]
Nthres [cm-3]
Schmidt
510-14
710-17
Ev+0.38
21010
Nagel
510-14
710-17
Ev+0.38
21010
Rein
3.610-15
710-17
Ev+0.394
21012
Impact of metal impurities
• Simulation approach
 Fe (PC1D) (J. Schmidt et al., Prog. Photovolt: Res. Appl. 13 (2005) p. 325)
 Fe, Cr, Au, Mo, Pt (PC1D) (H. Nagel et al., Proc. 20th EU-PVSEC 2005, p. 1271)
 Mo, Fe, Ti, Ni (PC1D) (S. Rein, Lifetime Spectroscopy, Springer 2005)
 Fe, Cr, Ni, Cu, Co (Sentaurus) (J. Schmidt et al., Proc. 38th IEEE-PVSC 2012)
SiNx
• Next generation of
n+
p-type Si
industrial silicon solar cells:
Al-p+
Standard industrial solar cell

Replacement of full-area Al-p+ BSF
by dielectric rear passivation,
such as Al2O3/SiNx

Implementation of a selective emitter
beneath metal contacts
n++
Al2O3/SiNx
Next-generation industrial
passivated emitter and rear cell (PERC)
Impact of metal impurities
• Simulation approach
 Fe (PC1D) (J. Schmidt et al., Prog. Photovolt: Res. Appl. 13 (2005) p. 325)
 Fe, Cr, Au, Mo, Pt (PC1D) (H. Nagel et al., Proc. 20th EU-PVSEC 2005, p. 1271)
 Mo, Fe, Ti, Ni (PC1D) (S. Rein, Lifetime Spectroscopy, Springer 2005)
 Fe, Cr, Ni, Cu, Co (Sentaurus) (J. Schmidt et al., Proc. 38th IEEE-PVSC 2012)
…
Impact of metal impurities
• Simulation approach
 Fe (PC1D) (J. Schmidt et al., Prog. Photovolt: Res. Appl. 13 (2005) p. 325)
 Fe, Cr, Au, Mo, Pt (PC1D) (H. Nagel et al., Proc. 20th EU-PVSEC 2005, p. 1271)
 Mo, Fe, Ti, Ni (PC1D) (S. Rein, Lifetime Spectroscopy, Springer 2005)
 Fe, Cr, Ni, Cu, Co (Sentaurus) (J. Schmidt et al., Proc. 38th IEEE-PVSC 2012)
…
Impact of metal impurities
• Simulation approach
 Fe (PC1D) (J. Schmidt et al., Prog. Photovolt: Res. Appl. 13 (2005) p. 325)
 Fe, Cr, Au, Mo, Pt (PC1D) (H. Nagel et al., Proc. 20th EU-PVSEC 2005, p. 1271)
 Mo, Fe, Ti, Ni (PC1D) (S. Rein, Lifetime Spectroscopy, Springer 2005)
 Fe, Cr, Ni, Cu, Co (Sentaurus) (J. Schmidt et al., Proc. 38th IEEE-PVSC 2012)
…
J. Schmidt, R. Krain, K. Bothe, G. Pensl, S. Beljakowa, J. Appl. Phys.102, 123701 (2007)
Impact of metal impurities
• Simulation approach
 Fe (PC1D) (J. Schmidt et al., Prog. Photovolt: Res. Appl. 13 (2005) p. 325)
 Fe, Cr, Au, Mo, Pt (PC1D) (H. Nagel et al., Proc. 20th EU-PVSEC 2005, p. 1271)
 Mo, Fe, Ti, Ni (PC1D) (S. Rein, Lifetime Spectroscopy, Springer 2005)
 Fe, Cr, Ni, Cu, Co (Sentaurus) (J. Schmidt et al., Proc. 38th IEEE-PVSC 2012)
 …22
22
21
21
Co
Ni
Fe
19
Cu
20
Efficiency [%]
Efficiency [%]
20
Cr
18
17
16
15
19
Ni
Co Cr
Fe
Cu
18
17
16
15
(a) p-Si base
14
1010
1011
1012
(b) n-Si base
1013
1014
1015
Metal impurity concentration [cm-3]
1016
14
1010
1011
1012
1013
1014
1015
Metal impurity concentration [cm-3]
1016
Impact of metal impurities
• Simulation approach
 Fe (PC1D) (J. Schmidt et al., Prog. Photovolt: Res. Appl. 13 (2005) p. 325)
 Fe, Cr, Au, Mo, Pt (PC1D) (H. Nagel et al., Proc. 20th EU-PVSEC 2005, p. 1271)
 Mo, Fe, Ti, Ni (PC1D) (S. Rein, Lifetime Spectroscopy, Springer 2005)
 Fe, Cr, Ni, Cu, Co (Sentaurus) (J. Schmidt et al., Proc. 38th IEEE-PVSC 2012)
 …22
22
21
21
Co
Ni
Fe
19
Cu
20
Efficiency [%]
Efficiency [%]
20
Cr
18
17
16
15
19
Ni
Co Cr
Fe
Cu
18
17
16
15
(a) p-Si base
14
1010
1011
1012
(b) n-Si base
1013
1014
1015
Metal impurity concentration [cm-3]
1016
14
1010
1011
1012
1013
1014
1015
Metal impurity concentration [cm-3]
1016
Summary
Fe
Cu
Cr
Nthres.Fe [cm-3]
Nthres.Cu [cm-3]
Nthres.Cr [cm-3]
Type of work
Author
Experiment
Davis
1980
PC1D Simulation
Schmidt
2005
21010
PC1D Simulation
Nagel
2005
21010
PC1D Simulation
Rein
2005
21012
Experiment
Coletti
2011
Experiment
Riepe
2011
Sentaurus Simulation
Schmidt
2012
Comparison of
Experiments
Coimparison of
Simulations
Wafer
total active
Feedstock
21014
Wafer
total active
Feedstock
11017
21010
1.21017
21017
(31014)
31010

0.91017
21017
11012
21014


Feedstock
11014
2.81017
11014
Wafer
total active
?
0.61017
11010


X

Conclusions
• Boron and oxygen content determines
bulk carrier lifetime in Cz silicon
• Curing increases lifetime considerably
• Threshold values for metallic impurity
concentrations similar for different experiments
• Comparibilty of simulations critically depends
defect parameters used
• Iron is the most widely studied impurity
• n-type Si is in general not less affected
by metals than p-type Si