EmanuelSachsFredFortFlowersandDanielFortFlowers

ProfessorofMechanicalEngineeringMIT

Photovoltaics; Opportunities and Challenges

Harnessing solar energy is critical

•  Covering0.2%ofthelandareaoftheUSwith20%efficientPVsystemswouldgeneratealltheelectricitythattheUSconsumes

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

MoldWafer

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.  Breakquality/

throughputtradeoff

2.  Reducecapitalcosts

3.  Producestandard‐sizewafer

Vertical ribbon growth Increasing Growth rate → Low Lifetime

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

Maximizegrowthrate→hightemperaturegradient&curvature → high stress

Tempe

rature

Height

Self-Aligned Cell

Self‐AlignedMetallizaUon

30µm fingers Texture and grooves in 1 step

Light-trapping texture guides precision metallization

9

Isotexture Issues •  Lighttrapping•  CosmeUcuniformityandconsistency

•  SawdamagesensiUvity

•  WaferqualitysensiUvity–  ShunUngatdislocaUons

•  InconsistentwithfuturePVdirecUons–  Reardielectrics–  Kerflesswafers

1366 Texture Solution •  Elegant,low‐cost,texturingtechnologytosimultaneously:

1.  Formhoneycombfronttextureo  Bestproventexturefor

mulU

2.  Polishtheback3.  Formfrontgroovesif

desiredo  Highperformance

metallizaUon

1366 Metallization Solution

•  SelfaligneddeposiUonofAgpasteintogrooves•  Platedfingers<40micronswidex10micronstall•  ContactresisUvity<0.001ohms‐cm2on100ohms/squniformemiaers–  NoneedforexpensiveselecUveemiaers

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

•  LargestManufofWindTurbines

•  LargestManufofsolarpanels

•  2%loanstobuildfactories

PV in China

•  Costofcapital•  Laborrate•  Costofrawmaterials•  PermicngandEnvironmental

TotalcostadvantagewithidenUcaltechnology~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

•  SellEquipment

•  PartneredwithRENA,globalleaderinwetprocessingforPV,basedinGermany

•  FirstproductlaunchscheduledforSept2010

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

•  LotsofUSinnovaUoninPV•  USmaybeabletosecureaposiUoninPVmanufacturingequipment

•  Incurrentenvironment,AsiawilldominatemanufacturingofPVproducts.

•  Economistsneedtotakeintoaccountcollateraldamageofmovingmanufacturingoffshore.

•  Lossofsupplychainjobs.•  Lossofindustrialcommons.