The Factory Hackathon: Manufacturing Innovation - Dozuki Workshop Series
Lasers in Solar Cell Manufacturing SolarNovus aspect of the manufacturing process that is critical...
Transcript of Lasers in Solar Cell Manufacturing SolarNovus aspect of the manufacturing process that is critical...
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LasersandSolarCellManufacturing
ByDickRieley,SalesManager,MidAltanticandSoutheastRegions,Ophir‐SpiriconLLC
TheGreenmovementisencouragingtheuseofenergyefficienttechnologiessuchassolarcells.Thistechnologyhasbeenmetwithresistanceduetoitsslowreturnoninvestment.Thisiscoupledwiththe
challengeoftheefficiencyofthematerialused.Reducingthecostofmanufacturingsolarcellsislargelyinfluencedbyproductionefficienciesaswellasthetypeofphotovoltaicmaterialsused.Manufacturingefficiencieshavebeenaddressedthroughhighspeed,nearlyfullyautomatedproductionprocessesfrom
handlingofthepanels,depositionofmaterials,tofinalpackaging.Theuseofcosteffectivephotovoltaicmaterials,however,representsarealdilemma.Thelowercostdepositionmaterialsarelessefficient,whereasthehigherefficiencymaterialscostmoreandcanpossesscarcinogenicelementsthatare
federallycontrolled.
Thesolarcellmanufacturingcommunity,althoughaddressingmoreefficientandenvironmentallysafe
materials,hasconcentratedonreducingcoststhroughautomatedprocesses.Thisrequiresmethodsthatareconsistentandreliable.Theriskoftheseoperations,however,isthattheycanproducealarge
quantityoflowcost,highqualitymaterialor,justasquickly,theycanproducesubstandardpanels.
Oneaspectofthemanufacturingprocessthatiscriticalisthescribingofthephotovoltaicmaterialontheindividualcellsonthelargepanels.Lasershaveproventobehighlyreliable,consistent,and
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predictableintheirproductionresults.Inthishighspeedmanufacturingarena,laserscaneasilykeepupwithproduction,aresilenttouse,andtypicallycontributetoacleanmanufacturingenvironment.
LaserBeamDiagnostics
However,withallthatlasershavetoofferandtheadvantagestheycanprovide,laserbeamdiagnostics
areanessentialpartoftheprocess,apartthatisoftenoverlooked.Therearetwokeydiagnosticmeasurementsthatareneededtoensurelaserconsistencyfrompaneltopanel:1)laserbeampower,and2)laserbeamdiagnostic‐size,shape,andintensity.
LaserPower:Thefirstmeasurement‐monitortheoutputpowerofthelaserusingaNISTcalibrated,
laserpowermeter.Regardlessofthequalityofthelaserbeam,ifthepowerisbelowspecification,thescribingprocesswillberejected.AsmostlaserscribersoperateatKHzrates,measuringaveragepowerissufficient.Thelaserpowerdetectorshouldhaveanactiveareatwicethesizeofthelaserbeam,with
adynamicmeasurementrangefrom100mWto100W,includingtheNISTcalibrationatthespecificoperationalwavelengthoftheprocess–typically1064nm,or532nm.Laserpower,whenmeasuredonaregularbasis,willprovideabenchmarkofprocessstabilityanduniformity.
WhenalaserpowermeteristiedintothemanufacturinglaserconsolusingUSB,automaticandperiodicmeasurementscanbetakenwithpass/failcriteriaestablishedforimmediatenotificationofameasurementoutofspecification.
LaserBeamDiagnostics:Alongwithlaserpower,thespatialinformationonthelaserbeamisequally
importanttomeasureandcontrol.Laserbeamdiagnosticstypicallyinvolvethreemeasurements;thelaserbeamsize,shape,andintensity.Intheproductionofsolarcells,thelaserbeamisusedtoscribe(ablate)thedepositedlayersofphotovoltaicmaterialdowntothebaseglass,therebyestablishingthe
individualelectricalcircuitcellsonthepanel.Withacontrolledbaselineofspatialmeasurements,theprocesscanbecontrolledwithoutallowingdeviationsinthelaserbeamthatcouldallowresidualmaterialinthescribeareapotentiallycausinganelectricalshortintheoverallpanelcircuit,resultingina
defectivepanel.
Themosttypicalmeasurementsthataremostinformativeforprocesscontrolinclude:
1)Thesizeofthelaserbeam.Theindustrystandardforbeammeasurementis13.5%ofPeak(1/e2).Thisisusefulasthecalculationisbasedonthepeakofthebeamwheretheprocessofablationis
performedandlesssoonthewingsofthebeam.
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2)Theelipticity(roundness)ofthelaserbeam.Shouldthebeamelipticitychangefromroundtoout‐of‐roundthentheablationpatternwillchangeandtheuniformityofthescribelineswillnotbeconsistent,
producingofout‐of‐specpanels.
3)Shapeoftheoverallbeam.Thiscanaffectthesizeandeffectivenessoftheablationpatternontheglasspanel.Theabovepictureisa3D/2DimageofatypicalTopHatBeamwheretheenergyisuniform
acrossthetopportionofthebeampattern.Thisisquiteusefulinpreparingauniformscribeofacertainwidthanddepth.Dependingupontheprocess,aGaussianBeampatternmaybecalledforaswell.IneithercaseabeamdiagnosticmeasurementthatcomparestheTopHatorGaussianshapetoanidealfit
isaveryinformativevalue.Trackingthesevaluestomonitorchangeisessentialforcloseandtightprocesscontrolofthesolarcelllaserprocess.
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http://www.ophiropt.com/photonics