HelioVolt has developed a novel reactive transfer processing technique called FASST to manufacture CIGS thin-film solar modules. This two-stage process involves independently depositing compound precursor layers, then rapidly reacting them through non-contact transfer synthesis to form high-efficiency CIGS. Recent results include 11.5% efficient production modules and a roadmap to reach 16% efficiency by 2014. The technique offers benefits over traditional CIGS methods like lower thermal budget, higher throughput, and improved materials utilization.
1. CIGS Manufacturing Technology
Matures: Perspective on Scaling
B.J. Stanbery
Chief Scientist, Founder, and Chairman
Printed Electronics/Photovoltaics USA 2010
2 December 2010; Santa Clara, CA
HelioVolt Confidential
and Proprietary
2. HelioVolt Corporate History
HelioVolt and NREL win
R&D 100 Award
Time Magazine’s “Best
Inventions of 2006”
Printed Electronics
Industry Award 1st production run
HelioVolt Wall Street Journal August 2009
founded Technology Award
12% cell 12% prototype module
11% production
efficiency and 14% cell efficiency
module efficiency
FASST® Process wins achieved achieved
achieved
Nano50 Award
2001 2003 2005 2006 2007 2008 2009 2010
Series A Series B Industry veteran Jim
funding funding Flanary joins as CEO
Commercial agreements
NREL CRADA Exclusive NREL Opened first factory in
signed for 3 years of
established IP Agreement Austin, Texas
production
Printed Electronics/PV USA 2Dec 2010
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3. HelioVolt Module Production Process
Module Out
Glass FASST® CIGS Module Final Assembly
Preparation Process Formation & Test
Glass In
Printed Electronics/PV USA 2Dec 2010
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4. Our CIGS Products vs. Alternatives
Our Process
Glass In Module Out
Glass FASST® CIGS Module Final Assembly
Preparation Process Formation & Test
Competitors’ CIGS Cell-Based Processes
Substrate In Module Out
Substrate CIGS Contact & Grid Final Assembly
Cell Cut & Sort Cell Stringing
Preparation Process Formation & Test
Silicon Process
Polysilicon Ingot Wafer Solar Cell Solar Module
Source: Wall Street research.
Printed Electronics/PV USA 2Dec 2010
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5. HelioVolt CIGS Thin-Film Products
P3 Monolithic Interconnect Structure
ZnO
P2 buffer
P1 CIGS
Moly
substrate
• Alloy of Copper, Indium, Gallium and Selenium
• Highest efficiency single-junction thin-film PV semiconductor material
– 20.3% conversion efficiency (ZSW)
• CIGS is one of three known intrinsically stable PV materials
(with Silicon and Gallium Arsenide)
– Intrinsic stability required for long lived robust products
• More efficient absorber of light than any other known semiconductor
• Requires 1/100th of the material compared to silicon for comparable
light absorption
Printed Electronics/PV USA 2Dec 2010
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6. Product Scaling and Performance Experience
14.0%
Cell
Efficiency
1364x scale-up
Cell 3.0%
3 Months
Prototype Module 12.0%
Scalability Proof
Efficiency
DONE
Prototype 4.5%
8x scale-up
2 Months
11.5%
Efficiency
7.8%
Module 2%
Production Module Progress 4 Months 10 Months
Commercial Production Size
NOW
Printed Electronics/PV USA 2Dec 2010
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7. 2010 Module Efficiency Progress
12% 120%
Max
11% 110% CV = Std Dev
Average
10% 100%
Coefficient of Variation (CV)
Average Efficiency
9% 90%
8% 80%
7% 70%
6% 60%
Equipment
5% 50%
CV Capability Upgrade
4% and 40%
3% Characterization 30%
2% 20%
1% 10%
0% 0%
MAY JUN JUL AUG SEP OCT NOV
2010
Efficiency: average, maximum, and distribution improved significantly month-to-month
Printed Electronics/PV USA 2Dec 2010
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8. 11.5% Champion Module Efficiency
75 Watts
75 W
11.5%
Printed Electronics/PV USA 2Dec 2010
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9. Pre-Certification Reliability Tests Complete
• Most recent modules
underwent Damp Heat (DH)
and Humidity Freeze (HF)
testing for pre-certification
reliability screening.
• DH Modules followed IEC
protocol 1000 hours at 85°C;
85% relative humidity.
• Humidity Freeze
– Half of the modules followed
IEC protocol for HF test alone.
– Half of the modules were
tested per IEC protocol with
1000Hrs DH, then 1000Hrs HF.
• No loss of power, Voc, Isc in
any screening tests.
Printed Electronics/PV USA 2Dec 2010
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10. HelioVolt Module Rooftop Test Array
Photograph of Factory Rooftop HelioVolt module test array.
Array tracks performance of HelioVolt, as well as, other thin-film
and silicon modules, and inverters
Printed Electronics/PV USA 2Dec 2010
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11. Multiple Proven Ways to Win
Performance Leader Next Gen Innovation
22%
• First generation
$1.2B players have
proven market
and value creation
Module Efficiency
$1.7B
$1.2B
14% $1.4B
• Opportunity for
technology
$9.2B
innovation to
trump incumbents
6% on both cost and
Low Margin Manufacturers High Margin Manufacturers performance
$2.00/w $1.00/w $0.50/w
Module Cost
Note: Market cap as of June 1, 2010.
Source: Wall Street research.
Printed Electronics/PV USA 2Dec 2010
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12. Roadmap to 16% Module Efficiency
18%
12%
Advanced TCO,
Enhanced
Transmission,
Ultrafast Heating, Light Trapping
Active Quenching, Predictive Design
6% Advanced
Composition
Baseline Process Grading Control
0%
2010 2011 2012 2013
• Development work based on HelioVolt patents and
trade secrets will drive module efficiency from 10% to 16%
• Applied Research – HelioVolt’s partnership with NREL will
drive module efficiency from 16% to 21%
Printed Electronics/PV USA 2Dec 2010
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13. Printed Electronics/Photovoltaics USA 2010
2 December 2010; Santa Clara, CA
MOTIVATION FOR ALTERNATIVE
APPROACH TO CIGS PROCESSING
Printed Electronics/PV USA 2Dec 2010
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14. Characteristics of an Ideal CIGS
Manufacturing Method
• High device-quality material
– Ability to create intrinsic defect structures limiting
recombination; role of the order-disorder transition?
– Ability to control Group III and VI composition gradients
– Control of extrinsic doping (e.g.: sodium)
• High processing rate
– Reduces capital cost for targeted throughput
• Low thermal budget
– Reduces operating cost and energy payback time
• High materials utilization
– Reduced materials consumption and recycling expenses
Printed Electronics/PV USA 2Dec 2010
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15. Synopsis of Prior Art for CIGS Synthesis:
Co-evaporation
• First method to achieve 10% efficiency and research
approach used to make all record cells since 1989
• Simultaneous evaporation of the constituent elements
onto a high-temperature (450-700°C) substrate to
directly synthesize CIGS in a single stage process
• Competition between adsorption and desorption
kinetics reduces (1) selenium utilization and
(2) indium incorporation at temperatures near/above
the order-disorder transition
• Extended dwell at high temperatures generates high
thermal budget and equipment costs
Printed Electronics/PV USA 2Dec 2010
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16. Synopsis of Prior Art for CIGS Synthesis:
Metal Precursor Selenization
• Most well-developed, widely used approach for
commercial manufacture of CIGS modules, providing
good large-area uniformity
• Deposition of multilayer metal films by PVD, plating, or
particle suspensions followed by second-stage
high-temperature annealing in Se or H2Se/H2S
• Complex intermetallic alloying reactions and
differential diffusion during selenization cause
uncontrolled segregation
• Selenium/Sulfur diffusion limits reaction rate and resulting
extended dwell at high temperature generates
high thermal budget; first stage deposition method
determines materials utilization efficiency and
capital intensity
Printed Electronics/PV USA 2Dec 2010
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17. Synopsis of Prior Art for CIGS Synthesis:
Oxide Precursor Selenization
• High-speed printing of copper indium gallium
oxide nanoparticle ink onto a metal foil substrate,
subsequently annealed at high temperature in
H2Se/H2S to convert the oxide into sulfo-selenide
– Enables excellent materials utilization
• Reduced diffusion lengths of chalcogens in
nanoparticles speeds displacement reaction
• Difficult recrystallization kinetics limit film
densification and large grain growth
• Composition gradient control challenging
Printed Electronics/PV USA 2Dec 2010
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18. Synopsis of Prior Art for CIGS Synthesis:
Stacked Elemental Layers (SEL)
• Differs from the metal selenization approaches by
incorporating layers of selenium, as well as the
metals, into the precursor film itself
– Circumvent the need to diffuse selenium through the
entire thickness of the precursor stack
– Enables intervention in intermetallic formation by
stacking sequence control
– Multi-step reaction kinetics shown to generate
compound intermediates prior to CIGS formation
• Rapid thermal processing used in second stage to
minimize thermal budget and parasitic reactions
Printed Electronics/PV USA 2Dec 2010
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20. Reactive Transfer Processing of
Compound Precursors
• Two-stage process Se, S
112 = Cu(In,Ga)(Se,S)2
– Low-temperature 247 = Cu2(In,Ga)4(Se,S)7
deposition of multilayer
compound precursor
Cu2Se3. .(In,Ga)2(Se,S)3
films CuSe. 112 .(In,Ga) (Se,S)
247
247
– RTP reaction of Cu2Se. .(In,Ga)4(Se,S)3
compound precursors
to form CIGS
Cu In, Ga
Intermetallic Plethora
Printed Electronics/PV USA 2Dec 2010
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21. FASST® Reactive Transfer Processing
Non-Contact Transfer (NCT™) Synthesis
Process Step
Cu, In,
Ga, Se • Independent deposition of distinct
compound precursor layers on
Substrate
substrate and source plate
Source Plate with Transfer Film • Rapid non-contact reaction
Pressure – Turns stack into CIGS with high efficiency grains
Heat – Combines benefits of sequential selenization
with Close-Spaced Vapor Transport (CSVT) for
junction optimization
Source Plate
• CIGS adheres to the substrate and
the source plate is reused
Substrate
CIGS Layer
A rapid manufacturing process reduces depreciation of capital
Printed Electronics/PV USA 2Dec 2010
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23. Reactive Transfer Processing
Compound Precursor Deposition
• Two methods have been developed for
deposition of compound precursors
– Low-temperature Co-evaporation
• Equipment requirements similar to conventional single-
stage co-evaporation but lower temperatures lead to
higher throughput and reduced thermal budget
– Liquid Metal-Organic molecular solutions
• Proprietary inks developed under NREL CRADA
• Decomposition of inks leads to formation of inorganic
compound precursor films nearly indistinguishable
from co-evaporated films (for some compounds)
Printed Electronics/PV USA 2Dec 2010
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24. MOD Comparison with Vacuum
Precursor Deposition Method
Co-evaporated Top View Top View Spray
CIGS Precursor Deposited
Film CIGS Precursor
Film
Cross Section Cross Section
Printed Electronics/PV USA 2Dec 2010
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25. Metal-Organic Decomposition
(MOD) Precursor Film Deposition
• Inorganic compound reaction CIGS synthesis provides
pathway for evolutionary adoption of MOD precursors
• Key drivers
– Low capital equipment cost
– Low thermal budget
– High throughput
• Flexibility
– Good compositional control by chemical synthesis
– Variety of Cu-, In- and Ga-containing inks can be synthesized
and densified to form multinary sulfo-selenide precursors
• Efficient use of materials
Printed Electronics/PV USA 2Dec 2010
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27. Device Quality CIGS in 30 Seconds:
First Ultra-Fast Heating Results
Printed Electronics/PV USA 2Dec 2010
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28. HelioVolt Highlights
• Disruptive CIGS technology
• Extensive CIGS intellectual property portfolio
• 9+ years and ~$145mm of R&D
• Unique technology commercialization partnership with
NREL
• Full-scale R&D line in Austin
• Deep technical team
• Technical Accomplishments – 11.5% efficiency champion
production module with >10.5% average efficiency
• Efficiency roadmap to 16%+ by 2014
• Plan for production expansion under development
Printed Electronics/PV USA 2Dec 2010
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