- Flexible PV modules for BIPV
- Potential for cost reductions and aesthetic integration
- Challenges for processing thin silicon wafer
Dr. Andrew Skumanich, SolarVision Consulting
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Thin film and thin wafer PV: challenges for BIPV applications [PV 2009]
1. Thin Films and Thin Wafers:
Challenges and
Opportunities with BIPV
PV Summit
June 3 rd 2009
Andy Skumanich, Ph.D.
SolarVision Consulting
SVC 2009 PV Summit Conference Page 1
2. Outline
Opportunities and challenges
• Market potential for BIPV
– Flexible PV modules
• Challenges
– Potential for cost reduction and aesthetic integration
• Thin film trajectory: CE and cost
– Various types including CIGS
• Ultra-thin wafer trajectory: thickness, CE, and cost
– PV processing sequence
– Handling considerations
• Conclusions
SVC 2009 PV Summit Conference Page 2
3. Market Opportunities
• General PV forecast: 6-9 GW in 2010
• Demand for glass: 2010 – 1Billion m2 WW
– Take 1/10% as BIPV, 10% CE
1GW of PV glass
• Roof-tops residential: coverage by PV
– 7 million new houses in typical year
– If 1/10% have BIPV roof, 10%CE
1GW of rooftop PV for residential
• BIPV could potentially be a major market driver
SVC 2009 PV Summit Conference Page 3
6. Challenges
• Thin Film:
– Improved efficiency
– Flexible substrate extends applications – maintain CE
– Viability of materials without exchange
• Wafer based c-Si:
– Foils which are flexible and robust
– Improved efficiency for ultra-thin wafers – recover CE
– Processing of wafers-to-cells
• Common
– Customizability in design
– Product range
SVC 2009 PV Summit Conference Page 6
7. Turn-key Landscape: TF & c-Si
a-Si and CIGS CdTe c-Si
Tandem
• Oerlikon (11) • Centrotherm • (Roth & Rau) Full chain:
• AMAT (14) • Centrotherm
• Ulvac (3) • Schmid
• Other misc
Multiple sub-
lines
SVC 2009 PV Summit Conference Page 7
8. Thin Film CE gains
• CIGS starting to show promise
– Turnkey line from Centrotherm
• a-Si needs to achieve >10% capability
• CdTe needs to confirm reliability
SVC 2009 PV Summit Conference Page 8
13. Cell Efficiency Roadmap
Cell Efficiency History and NREL Plan
Conversion Efficiency
25
SunPower
mono c-Si,
20
CE (%)
15
Mono -
10 crystalline
Multi -
crystalline
5
0
2002 2004 2006 2008 2010 2012
(Source: NREL Silicon Strategy, Dick Swanson – SunPower, SVC)
13
SVC 2009 PV Summit Conference Page 13
14. Ultra-thin wafer processing
• Aggressive activities world wide
– EU: Fraunhofer Institute
– Japan: NEDO
– USA: various including commercial companies
• Key developments: e.g. back surface treatment
– Example is GIT – Dr. Ajeet Rohatgi
SVC 2009 PV Summit Conference Page 14
15. GIT modeling for sub 100um wafers
• Bulk lifetime, thickness, BSRV and BSR targets for achieving 19-20% efficiency cells with
screen printed front contacts
21
Our Goal
20
19
Efficiency (%)
18
17 Current Status
lifetime=100us, BSRV=50cm/s, BSR=97%
16
lifetime=100us, BSRV=400cm/s, BSR=65%
15 lifetime=25us, BSRV=50cm/s, BSR=97%
lifetime=25us, BSRV=400cm/s, BSR=65%
14
0 100 200 300 400 500 GIT Dr.
Solar Cell Thickness (um)
Ajeet
Rohatgi
SVC 2009 PV Summit Conference Page 15
16. Roadmap to 20%-efficient c-Si solar
cells with screen printed contacts
22%
20.1% 20.0%
20% 19.3%
18.2%
18%
17.0%
Efficiency
16%
14%
12%
10%
Current Solar Improved Text, BSR (97%) High Sheet Res. Reduce Cell
Cell AR & SP BSRV Emitter (R=100 Thickness (100
GIT Dr.
(Ref=1.04% (100cm/s) ohm/sq) µm) Ajeet
FF=79.1% Rohatgi
M.C.=5.0)
SVC 2009 PV Summit Conference Page 16
17. New Process Vs Full Al BSF IQE & RetroRefl
100 100
90 90
80 80
New Full Al
70 Process BSF
70
Reflectance (%)
60 Voc(mV) 652 639 60
IQE (%)
Jsc(mA/cm 2) 39.4 37.9 New Process
50 50
FF(%) 78.1 78.9
40 Eff (%) 20.1 19.1 40
30 30
Full Al BSF
20 20
10 10 GIT Dr.
Ajeet
0 0
300 400 500 600 700 800 900 1000 1100 1200
Rohatgi
Wavelength (nm)
SVC 2009 PV Summit Conference Page 17
18. IV-curve for the best Screen Printed
New Process cell
0.16
0.14
0.12
0.10
? : 20.1 %
Isc (A)
0.08 VOC : 652 m V
JSC : 39.4 mA/cm2
0.06 FF : 78.1 %
0.04
0.02
0.00 GIT Dr.
0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 Ajeet
Voc (mV)
Rohatgi
Dielectric passivated rear LBSF raised the efficiency from 19.1 to 20.1%
SVC 2009 PV Summit Conference Page 18
19. Handling issues
• Breakage
– Of course the major concern for module manufacturers
• Warped wafers cause issues
– Ultra thin may have benefits and drawbacks
• Start-stop needs to be abrupt for high tpt
– Wafers act like “wings” during motion
• Multiple challenges for handling
SVC 2009 PV Summit Conference Page 19
20. Alternative Companies for Handling
• Equipment: Automation Technology Inc:
– Bernoulli grippers
– But still not developed
• Researchers at the Texas Manufacturing Assistance Center (University
of Texas, Arlington)
– prototype air system able to both acquire wafers from a stack and move
them along a track with no moving components
– contrasts with Bernoulli grippers which only acquire wafers and must use
manipulators and robotic elements to move wafers
SVC 2009 PV Summit Conference Page 20
21. Summary
• Decreasing thickness still moving forward
– Market leaders driving to wafers 150um and then below
– New improvements for thin films (CIGS specifically)
• Market forces will be pushing prices down
– Foreseeable future: more pressure on cost reduction
– Companies with tech advantages will survive
• Thin Film are steadily developing improved CE with
CIGS leading in CE, (not in market)
– Multiple challenges: higher CE >10% at low cost production
• Thin, and ultra-thin wafers now are driving processing
– Mulitple challenges: maintain CE below 100um, breakage
SVC 2009 PV Summit Conference Page 21
22. Conclusions
• Industry needs to drive metrics and dimensions
– BOS may be substantially lower for frame and labor
– May be closer to “grid parity” with lower BOS
• Increased focus on BIPV is also required
• Also, product portfolio needs to be expanded
– Flexible, multi-dimensional, etc.
• Current development capabilities can open up the
BIPV market in increase the demand for TF and ultra-
thin c-Si
SVC 2009 PV Summit Conference Page 22