Screen printed Ag fingers on phosp. Institute for Solar Energy ... Contamination
by screen printed Ag. (weak). Institute for ... x10-15 cm2 x10-15 cm2. Institute for ...
2nd Metallization workshop, Constance 2010
Effects of metallization in the semiconductor part – insights from experiments and device modeling
Felix Haase, Jens Müller, Pietro P. Altermatt,* Rolf Brendel * Leibniz University of Hannover, Dep. of Solar Energy Research Institute for Solar Energy Research Hamelin 1
Is a selective emitter necessary? Al-contact to c-Si
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Is a selective emitter necessary? Al-contact to c-Si
p-type
n-type
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Screen printed Ag fingers on phosphorous emitter
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Contamination by screen printed Ag
(weak)
M.M. Hilali, A. Rohatgi, S. Asher, IEEE TED 51, 948 (2004)
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Contamination by screen printed Ag
(weak)
Diffusivity [m2s-1]
T [ºC]
Ag
Li Fe
P 1/T [10-4 K-1] M.M. Hilali, A. Rohatgi, S. Asher, IEEE TED 51, 948 (2004)
F. Rollert et al, J. Phys. D 20, 1148 (1987)
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Recombination properties of Ag Ags
Ag0/-
σn = 7.5 ×10-15 cm2
Acceptor-like
Ag+/0
σp = 97 ×10-15 cm2
Donor-like
Yarykin et al, Phys. Rev. B 59, 5551 (1999)
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Recombination properties of Ag Ags
Ag0/-
σn = 7.5 ×10-15 cm2
Acceptor-like
Ag+/0
σp = 97 ×10-15 cm2
Donor-like
Macdonald and Geerlings, Appl. Phys. Lett. 85, 4061 (2004) Yarykin et al, Phys. Rev. B 59, 5551 (1999)
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Recombination properties of Ag Ags
Ag0/-
σn = 7.5 ×10-15 cm2
Acceptor-like
Ag+/0
σp = 97 ×10-15 cm2
Donor-like
Macdonald and Geerlings, Appl. Phys. Lett. 85, 4061 (2004) Yarykin et al, Phys. Rev. B 59, 5551 (1999)
Donor-like: σn/σp = 100/1 Acceptor-like: σn/σp = 1/100 Institute for Solar Energy Research Hamelin 9
Recombination properties of Ag Ags
Ag0/-
σn = 7.5 ×10-15 cm2
Acceptor-like
Ag+/0
σp = 97 ×10-15 cm2
Donor-like
Macdonald and Geerlings, Appl. Phys. Lett. 85, 4061 (2004) Yarykin et al, Phys. Rev. B 59, 5551 (1999)
Donor-like: σn/σp = 100/1 Acceptor-like: σn/σp = 1/100
σn
σp
Ag+/0
9700
97
Ag0/-
7.5
750
[10-15 cm2]
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Numerical device modeling Ag-contact Doping profiles Semiconductor simulation
Software: Sentaurus from Synopsys (former Dessis) TCAD P.P. Altermatt et al., EUPVSEC 24, 901 (2009)
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Numerical device modeling Ag-contact Doping profiles Semiconductor simulation
+ Circuit simulation
Software: Sentaurus from Synopsys (former Dessis) TCAD P.P. Altermatt et al., EUPVSEC 24, 901 (2009)
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Numerical device modeling Ag-contact Doping profiles Semiconductor simulation
+ Circuit simulation
= Software: Sentaurus from Synopsys (former Dessis) TCAD P.P. Altermatt et al., EUPVSEC 24, 901 (2009)
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Effect of Ag contamination Planar cells Jsc [mA/cm2] Hilali et al. experiment 45 Ω/sq
32.6
Voc [mV]
FF [%]
η [%]
627
78.5
16.0
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Effect of Ag contamination Planar cells Jsc [mA/cm2]
Voc [mV]
FF [%]
η [%]
Hilali et al. experiment 45 Ω/sq
32.6
627
78.5
16.0
Device modeling - with Ag
32.59
627.1
78.51
16.05
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Effect of Ag contamination Planar cells Jsc [mA/cm2]
Voc [mV]
FF [%]
η [%]
Hilali et al. experiment 45 Ω/sq
32.6
627
78.5
16.0
Device modeling - with Ag
32.59
627.1
78.51
16.05
629.9 78.38 ∆VOC = 2.8 mV
16.12
- without Ag
32.65
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Effect of Ag contamination Planar cells Jsc [mA/cm2]
Voc [mV]
FF [%]
η [%]
Hilali et al. experiment 45 Ω/sq
32.6
627
78.5
16.0
Device modeling - with Ag
32.59
627.1
78.51
16.05
629.9 78.38 ∆VOC = 2.8 mV
16.12
- without Ag
32.65
Hilali et al. experiment 100 Ω/sq 33.9
627
77.5
16.5
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Effect of Ag contamination Planar cells Jsc [mA/cm2]
Voc [mV]
FF [%]
η [%]
Hilali et al. experiment 45 Ω/sq
32.6
627
78.5
16.0
Device modeling - with Ag
32.59
627.1
78.51
16.05
629.9 78.38 ∆VOC = 2.8 mV
16.12
- without Ag
32.65
Hilali et al. experiment 100 Ω/sq 33.9
627
77.5
16.5
Device modeling - with Ag
627.6
77.56
16.48
33.86
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Effect of Ag contamination Planar cells Jsc [mA/cm2]
Voc [mV]
FF [%]
η [%]
Hilali et al. experiment 45 Ω/sq
32.6
627
78.5
16.0
Device modeling - with Ag
32.59
627.1
78.51
16.05
629.9 78.38 ∆VOC = 2.8 mV
16.12
- without Ag
32.65
Hilali et al. experiment 100 Ω/sq 33.9
627
77.5
16.5
Device modeling - with Ag
33.86
627.6
77.56
16.48
33.93
641.0
76.89
16.72
- without Ag
∆VOC = 13.4 mV Institute for Solar Energy Research Hamelin 19
Impact on cell with optimized emitter
Dominant recombination factors in cells with p-type p Cz base: Current cell designs Emitter J0 [fA/cm2] BSF J0 [fA/cm2] Dominant recombination
Future cell designs
900-1700
6 A/cm2
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Current-flow through point-contact contact
J > 4 A/cm2
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Current-flow through point-contact contact
J > 3 A/cm2
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Current-flow through point-contact contact
J > 3 A/cm2
Active area smaller than contact area → small resistive losses Institute for Solar Energy Research Hamelin 38
Recombination losses at contact Sample preparation: a-Si/SiN passivation d = 100 µm to 300 µm
c-Si (FZ, p-type, Ndop = 6x1013 cm-3) Al (evaporated by e-gun)
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Recombination losses at contact Sample preparation: a-Si/SiN passivation d = 100 µm to 300 µm
c-Si (FZ, p-type, Ndop = 6x1013 cm-3) Al (evaporated by e-gun)
Annealing at 300°C for 10 min
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Recombination losses at contact Sample preparation: a-Si/SiN passivation d = 100 µm to 300 µm
c-Si (FZ, p-type, Ndop = 6x1013 cm-3) Al (evaporated by e-gun)
Annealing at 300°C for 10 min QSSPC measurement not possible because of metal at the rear side
Institute for Solar Energy Research Hamelin 41
Recombination losses at contact Sample preparation: a-Si/SiN passivation d = 100 µm to 300 µm
c-Si (FZ, p-type, Ndop = 6x1013 cm-3) Al (evaporated by e-gun)
Annealing at 300°C for 10 min QSSPC measurement not possible because of metal at the rear side Measurement of effective lifetime with Infrared Lifetime Mapping (ILM) K. Ramspeck et al., EUPVSEC 24, 871 (2009) J. Mueller, to be published
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Experimental results
Simulations cannot reproduce measurements with:
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Experimental results
Simulations cannot reproduce measurements with: • an abrupt c-Si/Al interface
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Experimental results
Simulations cannot reproduce measurements with: • an abrupt c-Si/Al interface • Schottky contacts
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Al-BSF due to annealing
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Al-BSF due to annealing
Extrapolation to annealing temperature
Miller and Savage, J. Appl. Phys. 27, 1430 (1956)
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Al-BSF due to annealing
Al profile for simulations: Extrapolation to annealing temperature
• Ndop-peak: 1x1015 cm-3 to 3x1015 cm-3 • d = 0.01 µm to 0.1 µm
Miller and Savage, J. Appl. Phys. 27, 1430 (1956)
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Simulation results
Surface recombination velocity: • Seff = 2x105 cm/s • Seff < Stherm = 107 cm/s • most PERC cells can be simulated only with this effect!
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Conclusions
• Optimized 100 Ω/sq emitters with silver contamination due to firing of current screen printed contacts:
∆VOC = -13 mV with silver
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Conclusions
• Optimized 100 Ω/sq emitters with silver contamination due to firing of current screen printed contacts:
∆VOC = -13 mV with silver • p-type type Cz base must have at least a weak BSF (e.g. by annealing) and local contacts to reach high efficiencies
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Conclusions
• Optimized 100 Ω/sq emitters with silver contamination due to firing of current screen printed contacts:
∆VOC = -13 mV with silver • p-type type Cz base must have at least a weak BSF (e.g. by annealing) and local contacts to reach high efficiencies • Evaporated Al contacts annealed at 300° 300 C on 6x1013 cm-3 boron doped Si wafer show BSF Essential to explain good performance of most PERC cells: cells Seff = 2x105 cm/s < Stherm =107 cm/s
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Thank you for your attention
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