Emanuel
Sachs
 Fred
Fort
Flowers
and
Daniel
Fort
Flowers


Professor
of
Mechanical
Engineering
 MIT



Photovoltaics; Opportunities and Challenges

Harnessing solar energy is critical

•  Covering
0.2%
of
the
land
area
of
the
US
with
20%
 efficient
PV
systems
would
generate
all
the
electricity
 that
the
US
consumes


History and Status of Silicon PV

*LCOE calculated assuming 5.75kWh/m2/day (17% capacity factor), a 7% discount rate, and a 30-year project life.

Solar at the cost of coal

Wafers; Sawn ingots vs. Kerfless Current Silicon-Wafer Process

Cast Ingot Cut Brick

5


Saw Wafers Clean & Damage Etch Wafers

2X of Everything for

1 Wafer

Silicon to Wafer in 1 Machine

Mold
 Wafer


Pure Silicon

50% contaminated

waste

Pure Silicon

1366 Direct Wafer (DW)

Direct Wafer: Timeline

1/09 Dec Conception

First Tin Wafers

First Silicon Wafers

Win $500k NREL

Win $4M

ARPA-E

First cells

1/10 6” furnace design and build

Scale to 3” wafers

12.5% cells

15-16% on 6”

wafers

String Ribbon silicon Issues:
 1.  Break
quality
/


throughput
tradeoff


2.  Reduce
capital
costs


3.  Produce
standard‐size
 wafer


Vertical ribbon growth Increasing Growth rate → Low Lifetime

→ high dislocation density → low lifetime (after Bentzen, J. Appl Phys. 99)

Maximize
growth
rate


→


high
temperature
gradient
&
curvature

 → high stress

Te m pe

ra tu re

Height

Self-Aligned Cell

Self‐Aligned
 MetallizaUon


30µm fingers Texture and grooves in 1 step

Light-trapping texture guides precision metallization

9


Isotexture Issues •  Light
trapping
 •  CosmeUc
uniformity
and
 consistency


•  Saw
damage
sensiUvity
 •  Wafer
quality
sensiUvity


–  ShunUng
at
dislocaUons
 •  Inconsistent
with
future
PV
 direcUons
 –  Rear
dielectrics
 –  Kerfless
wafers


1366 Texture Solution •  Elegant,
low‐cost,
texturing
 technology
to
simultaneously:


1.  Form
honeycomb
front
 texture
 o  Best
proven
texture
for


mulU


2.  Polish
the
back
 3.  Form
front
grooves
if


desired
 o  High
performance


metallizaUon


1366 Metallization Solution

•  Self
aligned
deposiUon
of
Ag
paste
into
grooves
 •  Plated
fingers


China Leading Global Race to Make Clean Energy Jan 30, 2010

•  Largest
Manuf
of
Wind
 Turbines


•  Largest
Manuf
of
solar
 panels


•  2%
loans
to
build
 factories


PV in China

•  Cost
of
capital
 •  Labor
rate
 •  Cost
of
raw
materials
 •  Permicng
and
Environmental


Total
cost
advantage
with
idenUcal
 technology
~30%


Basic Science; US Dominates

Balance of Trade??

Can Silicon PV be Manufactured in US Silicon is >80% of PV market,

but US trails Asia/Europe

Source: Photon International

1366 Strategy in Cell Making

•  Sell
Equipment
 •  Partnered
with
RENA,
global
leader
in
wet
 processing
for
PV,
based
in
Germany


•  First
product
launch
scheduled
for
Sept
2010


U.S. In Manufacturing: The Bigger Picture

Restoring American Competitiveness Gary Pisano and Willy Shih Harvard Business Review, July-Aug 2009.

•  Decades of outsourcing manufacturing has left U.S. industry without the means to invent the next generation of high-tech products that are key to rebuilding its economy”

•  Industrial Commons: the collective R&D, engineering, and manufacturing capabilities that sustain innovation

Summary

•  Lots
of
US
innovaUon
in
PV
 •  US
may
be
able
to
secure
a
posiUon
in
PV
 manufacturing
equipment


•  In
current
environment,
Asia
will
dominate
 manufacturing
of
PV
products.


•  Economists
need
to
take
into
account
collateral
 damage
of
moving
manufacturing
offshore.


•  Loss
of
supply
chain
jobs.
 •  Loss
of
industrial
commons.