SPIE Optoelectronic Integrated Circuits 2011 HelioVolt Presentation

January 27, 2011

Thin Film CIGS Photovoltaic Modules:
Monolithic Integration and Advanced Packaging
for High Performance, High Reliability and Low Cost
Louay Eldada
Chief Technology Officer

© 2011 HelioVolt Corporation 1

Next Generation High-Performance
and Low-Cost Solar Technology
• Disruptive CIGS PV technology: high efficiency low cost monolithic modules
• Extensive CIGS intellectual property portfolio
• 9+ years and ~$145MM of R&D
• Unique technology commercialization partnership with NREL
• Fully equipped production line and R&D line in Austin
• Team with deep technical expertise
• NREL-confirmed ~12% (11.8±0.6%) efficiency champion production module,
with 10.8% average efficiency
• Efficiency roadmap to 16%+ in 2014
• Plan for production expansion under development


Competitive Technology Advantage
• FASST® CIGS process advantages
Glass In
– Two-stage process provides maximum flexibility to optimize precursor
deposition method and composition of each layer: higher efficiency
– Most rapid synthesis of CIGS from precursors of any method:
reduces capital costs
Glass – Demonstrated state of the art crystalline quality: higher efficiency
Preparation

FASST® CIGS
– Unique, rapid, flexible optimization of CIGS surface quality: higher
Process efficiency
Module • Advanced NREL liquid precursor technology
Formation
– Reduces capital costs and COGS
Final Assembly
& Test • Monolithic module circuit integration
– Reduces module assembly costs compared to discrete cell assembly
• Advanced module packaging
– Unique, high performance encapsulant, edge sealant, and potting
compound supports product lifetime beyond standard 25 year warranty:
Module Out
reduces cost of electricity (¢/kWh)


CIGS: Highest Thin Film Efficiency
Mono-Crystalline Si

Multi-Crystalline Si

CIGS

CdTe

a-Si/Micro

a-Si 1-j

0% 5% 10% 15% 20% 25%

2010 Module Efficiency Record Cell Efficiency

Source: Greentech Media, Prometheus Institute and Wall Street research.


CIGS Contenders Approach
Process
Company Substrate Cell or Module
Technology

Co-evaporation Glass Module

Co-evaporation Glass Tubular “Module”

Selenization Glass Module

Sputtering Steel Foil Cell

Nanoparticle
Metal Foil Cell
Sintering

Electroplating Steel Foil Cell

HelioVolt FASST® Currently Glass Module


CIGS Contenders Results
CIGS Deposition Typical Module
Company COGS CapEx
Uniformity Efficiency

High High High 10-12%

Moderate High High 9%

Moderate Moderate High 10-12%

Low Moderate High 10%

Low Moderate Moderate 9%

Low Moderate Moderate 9%

High Low Low 10-12%


Monolithic Integration is Key to Cost Leadership
and Product Reliability
HelioVolt Process Competitors’ CIGS Cell-Based Processes

Glass In Glass In Additional Costs
Stainless steel foil $0.08
Glass Substrate
$0.06 $0.06
Preparation Preparation
Higher non-material
FASST® CIGS CIGS ?
$0.07 $0.15 inputs (e.g. labor)
Process Process

Module $0.01 Contact & Grid $0.01
Formation
Higher yield loss ?
Formation

Final Assembly $0.13 ?
Cell Cut & Sort Stringing material $0.12
& Test

Total: $0.27/Wp Cell Stringing $0.12 Two encapsulant layers
$0.04
and outer frame
Final Assembly
$0.17
& Test
Module Out Add’l: $0.24+/Wp

Total: $0.51+/Wp

Module Out
Note: Input materials cost / Wp in cents.


HelioVolt PV Module Production Line

Moly Deposition Exit Precursor Deposition Load FASST® Processor Load

FASST® Processor Unload Buffer Load Final PVIC Pattern Step

PVIC Lamination Junction Box Attach Final Eff. Test


FASST® Reactive Transfer Process
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 structure
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

Rapid manufacturing process reduces capital amortization cost


CIGS Material Fundamentals

CuInSe2 chalcopyrite crystal structure: T–X section of the phase diagram along the
(a) conventional unit cell of height c, with a Cu2Se-In2Se3 pseudobinary section of the
square base of width a Cu–In–Se chemical system.
(b) cation-centered first coordination shell : CuInSe2 chalcopyrite phase
(c) anion-centered first coordination shell : In-rich/Cu-poor (Cu2In4Se7 & CuIn3Se5)
showing bond lengths dCu–Se and dIn–Se. ordered defect compound (ODC) phase

B.J. Stanbery, Critical Reviews in Solid State and Materials Sciences, 27(2):73-117 (2002)


Role of Micro and Nanostructuring
in CIGS PV Device Operation
Observations on Device-Quality ( >15%) CIGS:
 Large columnar grains
 Copper deficiency compared to -CuInSe2
 Compositions lie in the equilibrium 2-phase domain:
domains, Cu-rich with p-type conductivity and
domains, Cu-poor with n-type conductivity,
form nanoscale p-n junction networks*;
n-type networks act as preferential electron pathways,
p-type networks act as preferential hole pathways,
positive and negative charges travel to the contacts in
physically separated paths, reducing recombination

*Intra-Absorber Junction (IAJ) model, APL 87, 121904 (2005)


Composition Fluctuations and Carrier
Transport in CIGS PV Absorbers
Experimental results* HAADF-TEM
& Nanoscale EDS
– 5-10 nm characteristic domain size
– Chemical composition fluctuations
found across the domains
p1: Cu:In:Ga:Se=31:14:7:48
p2: Cu:In:Ga:Se=27:15:9:49
p3: Cu:In:Ga:Se=30:15:6:49
– Dark domains are relatively Cu rich, *Applied Physics Letters, 87, 2005, 121904
bright domains are relatively Cu poor
HAADF-TEM: High-Angle Annular Dark-Field Transmission Electron Microscopy
EDS: Energy-Dispersive X-ray Spectroscopy


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
(Cooperative Research And Development Agreement)
– Decomposition of inks leads to formation of inorganic
compound precursor films nearly indistinguishable from
co-evaporated films (for some compounds)


Recrystallization of Nanoscale Vacuum
Precursor Films Forming Large Grain CIGS

Precursor Film FASST® CIGS cross-section


HelioVolt-NREL CRADA Technology
Advantages
• Atmospheric (non-vacuum) processes
– Low capital equipment cost, 10-20x reduction vs. vacuum equipment
– Low thermal budget, low energy consumption
– Small footprint, 5-10x reduction vs. vacuum equipment
– High uptime
– High throughput
• Inks
– Good compositional control by chemical synthesis
– A variety of materials can be synthesized; we have proprietary Cu-, In-
and Ga-containing inks that densify to multinary selenide precursors
• Efficient use of materials
– >95% material utilization vs. 80% for sputtering, 60% for evaporation


Printed Electronics Equipment & Processes
Leveraged in PV
Printed Electronics Conventional Electronics
Simple Circuitry Complex Circuitry

– Slow or static circuits – Fast switching circuits
– Low integration density – High integration density
– Large areas – Small areas
– Rigid or flexible substrates – Rigid substrates
– Simple fabrication – Complex fabrication
– Low fabrication cost – High fabrication cost

Low Cost High Cost


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


Deposition of PV Inks
Preferred methods for printing CIGS precursor ink thin films

Ultrasonic Atomization Spraying

Slot Die Extrusion Coating


PVD vs. Ink Precursor Deposition
PVD Deposited Spray Deposited
CIGS Precursor Film CIGS Precursor Film
Top View Top View

Cross Section Cross Section


NREL CRADA – Hybrid CIGS by FASST®

XRD
• Chalcopyrite CIGS (& Mo)
SEM • (220/204) preferred orientation, helps
• Exceptionally large grains junction formation and improves solar
• Columnar structure cell performance

Hybrid CIGS efficiency reached parity with PVD-based CIGS


Device Quality CIGS in 30 Seconds:
First Ultra-Fast Heating Results with Rapid Optical Processor (ROP)


FASST® Yields High-Quality CIGS

QE curve
Good carrier collection

SEM
Large, columnar grains


Cd-Free Buffer for a Cd-Free Product

CdS buffer
Cd-free buffer

Uniform conformal Cd-free buffer
on CIGS

Quantum Efficiency (QE) of CIGS with Cd-free
buffer shows improvement over CdS, especially
in the 400-500 nm wavelength range


Uniform High-Quality CIGS Polycrystalline Films
Deliver 14% Cell Efficiency
Current Density (A/cm2)

Voc = 631 mV
Jsc = 31 mA/cm2
FF = 72%
Eff = 14%

Voltage (V)


Sputtered Back Contact (Mo)

Cu-In-Ga-Se Precursor Films
Pattern 1 (Laser Scribe)
Module Fab Process Flow
CIGS by FASST Reactive Transfer

Buffer Layers
Pattern 2 (Mech. Scribe)
Sputtered Front Contact (TCO)
Pattern 3 (Mech. Scribe)
Bus Bars and Tabs

PVIC
PVIC Test

Edge Sealant Application Glass In Module Out

Encapsulant Application

= 2.5 hrs
Lamination

Final Test

Quality Control


Photovoltaic Integrated Circuit (PVIC) Typical manufacturing steps of monolithic
interconnection for CIGS PV modules

Cell
Length
W.N. Shafarman et al., „Cu(InGa)Se2 Solar Cells‟ in Handbook of Photovoltaic Science and Engineering (2003)

Scribe
Zone
TCO Window

–

–

–

–
–
Buffer
Cell Width

–
P3
CIGS Absorber P2
–

Back Contact P1

–
Substrate

Bus Bar
Segment Isolation & Interconnection Scribes
+ - and Charge Transport


Modeling for Device/Module Design
• HelioVolt CIGS device/module design further improved by various
modeling methods, e.g. 2-D circuit design, device physics modeling, and
thermodynamics modeling
Circuit model Segment/Cell Sub-cell network
TCO network
Module

Mo network

Sub-cell 80 66

Module Power Output (W)
79 65.5

Module FF (%)
78 65
77 64.5
76 Power 64
FF (%)
75 63.5
8 10 12 14 16 18 20 22
TCO Sheet Resistance (Ω/□)


Product Scaling and Performance Experience
14%
Cell
0.66cm2

Efficiency
1364x scale-up
Cell 3%

3 Months

Prototype Module 12%
30cmx30cm

Efficiency
Scalability Proof 5%
Prototype
8x scale-up
2 Months

12%

Efficiency
8%

Module 2%
Production Module Progress 4 Months 10 Months
1.2mx0.6m

Commercial Production Size


FASST® CIGS Production Modules 120x60 cm Module 2

Top view with SEM

Cross-sectional
SEM view

Faceted CIGS crystals absorb light efficiently
Large grains from all directions from dawn to dusk, giving
with no horizontal HelioVolt CIGS its characteristic black color
grain boundaries
support high efficiency


Production Module Results in Last Year
12
Average Efficiency
11 Continuously
Increasing
10 Equipment
Upgraded
9

8
Efficiency (%)
Efficiency (%)

7

6

5

4

3

2

1

0
113

127

141

155

169

183

197
106

120

134

148

162

176

190

204
211
218
225
232
239
246
253
260
267
274
281
288
295
302
309
316
323
330
337
344
351
358
365
372
379
386
393
1
8
15

29

43

57

71

85

99
22

36

50

64

78

92

G2 Modules – Feb ’10-present
G2 Modules – Feb 2010-present


G2 Module Efficiency Progress
12% Max 120%
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% 40%
and
3% 30%
Characterization
2% 20%
1% 10%
0% 0%
MAY JUN JUL AUG SEP OCT NOV
2010
 Efficiency: continuous improvement in efficiency average, maximum, and distribution


12% HelioVolt G2 Module Efficiency
– NREL Measurement –

12% module independently verified by NREL (11.8±0.6%)


Best-In-Class Proprietary Packaging
• Edge Sealing: HVC has unique edge sealant
solution that guarantees 25 year lifetime in high
humidity environments
• Lamination: HVC has unique encapsulant sheet
with high optical transparency, light trapping
capability, good chemical compatibility with thin
films, and outstanding ability to keep moisture out
and withstand UV exposure
• Junction box: HVC has a J-box that is proven in the
field; includes bypass diode to protect string from
partial shading losses
• Front glass: HVC uses high-transparency low-iron
tempered superstrate glass for highest optical
performance and reliability


HelioVolt CIGS Module Product Spec
Electrical Performance * HVC-170X
Maximum Power – Pmax 68.0 Watts
Open Circuit Voltage – Voc 74.5 Volts
Short Circuit Current – Isc 1.5 Amps
Operating Voltage – Vmp 55.0 Volts
Current at Operating Voltage – Imp 1.24 Amps
Maximum System Voltage – UL 600 Volts
Maximum System Voltage – IEC 1000 Volts
*Standard Test Conditions (STC). Ratings are +/-10%.

Physical & Mechanical Specifications HVC-170X
Length 1210 mm
Width 601 mm
Thickness 6.7 mm
Area 0.73 m2
Weight 12.3 kg
Positive Leadwire Length 660 mm
Negative Leadwire Length 660 mm
HVC-170X
Connectors MC-4
Bypass Diode Yes • Construction: Glass-glass laminate
Cell Type CIGS • Certification: IEC 61646, IEC 61730,
Frame None UL 1703, UL 790 Class A fire rating,
Cover Type Tempered Glass CEC listing, CE mark in process
• Warranty: 25 years
Encapsulation Edge Seal/Thermoplastic


Certification Testing
Description
Test
(per UL/IEC requirements)
Performance +/- 10% of specified electrical parameters
Outdoor Exposure 60 kWh/m2, maintain performance
Thermal Cycling • -40 to +90°C
Temperature & RH Environmental Testing Damp Heat • 85°C / 85%RH
Humidity Freeze • -40 to +90°C w/ condensation
Mechanical • Shading hot spot
Robustness • Connectors/J-box pull test
• Mech loading: 400 lbs, 30 minutes
• Impact: 2” 1.18 lb steel ball, 51” drop
Impact Testing
Shock Hazard • No leakage current after
environmental exposure

UL 1703: Flat-Plate Photovoltaic Modules and Panels
IEC 61646: Thin-film Terrestrial Photovoltaic (PV) Modules
– Design Qualification and Type Approval
IEC 61730: PV Module – Safety Qualification
Mechanical Load Testing UL: Underwriters Laboratories, IEC: International Electrotechnical Commission


Completed Reliability Screening Tests
% of Initial Pmax, Light Soak Stabilized
• Completed Damp Heat (DH) and DH Test
Humidity Freeze (HF) testing for pre- 120%
99.9%
100% 89.9% 87.5%
certification reliability screening

% of Initial Pmax
80%

• DH Test: 60%
40%
– Followed IEC protocol 1000 hrs 85°C, 20%

85% RH (Relative Humidity) 0%
HelioVolt Competitor A Competitor B
– Passed with virtually no degradation Module Manufacturer
DH
• HF Test:
% of Initial Pmax, Light Soak Stabilized
– All modules followed IEC protocol, HF Test and DH+HF Test
which includes 50 cycles of thermal 120% 107.1%
98.2%
cycling (TC*) pre-conditioning, 100%
Double
% of Initial Pmax 80%
followed by 10 cycles of HF** torture not
60% required in
– Half of the modules had additionally 40%
certification
gone through 1000 hrs of IEC DH test testing
20%

– Passed with no degradation: 0%

No loss of Power, Voc, Isc HF Exposure Only DH + HF Exposure

* TC cycle: -40°C to 85°C, 10min dwell at extremes
** HF cycle: -40°C to 85°C/85%RH, 30min dwell at -40°C, 20hr dwell at 85°C/85%RH HF DH+HF


HelioVolt Module Rooftop Test Array

Factory Rooftop HelioVolt module test array. Array tracks performance of
HelioVolt, as well as other thin-film and silicon modules, and inverters


HV Rooftop Test Facility
STATUS CAPABILITIES
• Phase 1 installation complete • Irradiance
• ProSolar, Schletter, and CoolPly – Plane of Array (POA)
racking – Global Total (GT)
• Xantrex, SMA, Fronius Inverters • Weather
• Competitor and HelioVolt modules – Temperature
• 10kW initial capacity – Relative Humidity
• Thorough monitoring of energy • Electrical
harvest and weather conditions – DC Voltage
– DC Current
– AC Voltage
– AC Current
– Inverter Efficiency


HelioVolt Modules
(20° tilt, ballasted, Schletter racking)
• 32 HelioVolt modules in 4 strings on Schletter racking
• Full light soak effect achieved on first day


Rooftop Performance –
Comparison of All Arrays
One Day Comparison, All Arrays

HelioVolt CIGS
Tier 1 mc-Si
Tier 1 CdTe
2nd Glass Laminate CIGS
Tubular CIGS

• HelioVolt modules have highest yield, followed by Tier
1 mc-Si modules; CdTe & other CIGS lag behind


Roadmap to 16% Module Efficiency
18%

12%
Advanced TCO,
Enhanced
Transmission,
Ultrafast Heating, Light Trapping
Active Predictive Design
Quenching,
6% Advanced
Baseline Process Composition
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%


Product Portfolio Built on
Standard Component Platform
Commercial Rooftop Systems Utility Scale

BIPV – Sunshades BIPV – Spandrels
Parking Structures 5‟X5‟

1‟X1‟
300mm CIGS PVIC

2‟X4‟

• Front view
• 5‟x5‟ Element
• Framing provided by curtain wall manufacturer
• Standard or custom element


Product Portfolio Evolution
2011 2012 2013 2014

Standard modules for commercial
rooftops and utility applications.

Standard modules offered with system level
solutions for commercial rooftops (including
mounting, power management).
New standard component introduced to
reduce balance of systems costs.

Standard modules adapted for BIPV
applications (facades, sunshades, roof
tiles) including BIPV components with
integrated power management.

Efficiency 11% 12% 14% 16%


Acknowledgments
• Dr. Keith Emery and his team for the module efficiency
verification testing
National Renewable Energy Laboratory
• Prof. James Sites and his team for the help with cell
characterization
Colorado State University
• Dr. David S. Ginley and his team for the CRADA work on
ink development
National Renewable Energy Laboratory
• The entire HelioVolt team for their role in the successful
scale up of the CIGS reactive transfer technology
HelioVolt Corporation


Thank You!
Louay Eldada
leldada@heliovolt.com
(512) 767-6060


SPIE Optoelectronic Integrated Circuits 2011 HelioVolt Presentation

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