Master’sThesisPresentation
13,July,2016
ComparisonOfNovelAndStateOfTheArtSolarCells
Author:AdegbenroAyodejiREMENABatch8- 33356695
Supervisors:Prof.Dr.NadiaH.RafatProf.Dr.HartmutHillmer
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AbbreviationØc-Si– CrystallineSilicon
Øa-Si:H– HydrogenatedAmorphousSilicon
ØCdTe– CadmiumTelluride
ØCIGS– CopperIndiumGalliumSelenide
ØDSSC– DyeSensitizeSolarCells
ØGaAs– GalliumArsenide
ØHIT– HeterojunctionIntrinsicThinlayer
ØEPBT– Energypaybacktime
ØGHG– Greenhousegases2
OUTLINE
ØObjectiveofresearch
ØCurrentstatusofevaluatedPVcells
ØSimulationofHITsolarcell
ØWeighingfactors
ØFutureprospectsofHITsolarcell
ØSummaryandConclusion
ØBibliography 3
Objectiveofresearch
• Theobjectiveofthisresearchworkistocompareandshowthe
possibilityofhetero-junctionintrinsicthinlayer(HIT)solarcells
overcomingc-SisolarcellsinthePVindustrybasedonitslow
thermalbudget,higherconversionefficiency(viaPC1D)and
possibilityofthinnersiliconlayers.
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OUTLINE
ØObjectiveofresearch
ØCurrentstatusofevaluatedPVcells
ØSimulationofHITsolarcell
ØWeighingfactors
ØFutureprospectsofHITsolarcell
ØSummaryandConclusion
ØBibliography 5
Crystallinesiliconsolarcells:- monocrystalline&polycrystalline
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+93%shareofPVmarketasat2015
+Cellandmoduleefficiencyrangesbetween20-25%and12-19%respectively
+Evidenceofdurabilityandlongevityintoughoutdoorconditions
+Productionscale59GWp[2]- Highlevelofembodiedenergyinproduction
- Complexandintricatetofabricatehttp://www.123rf.com/photo_27734440_polycrystalline-solar-cell-3x6-for-diy-solar-panel-isolated-on-white-background.html
Thin filmsolarcells:- a-Si:H,CdTe,CIGS
+Promisinglowcostsolarcells
+Absorptioncoefficientmuchhigherthanc-Sisolarcells
+Easierprocessingstep
+Productionscale>4.2GWp(aSi-1.1Wp,CdTe-2.5Wp,CIGS-0.6Wp)[2]
+Possibilityofdoublejunctionstructure
- Cellefficienciesranging(9-15%)andmuchloweratmodulelevel
- PronetoStaebler-Wronskieffect 7http://materia.nl/article/innovation-thin-film-solar-cells-at-mx2016/, http://www.asmac.com.hk/thin-film-solar-cell.php
GaAs Multi-junction
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+Utilizeshort,mediumandlongwavelengthofthelightspectrum
- Expensivematerialsandintricateprocessingsteps
+Solarcellefficiencyover30%(concentratorandnonconcentrator)
+Excellentforhightemperatureapplications
+Possibilityofdifferentjunctionformation
+Spaceapplicationsandconcentratorsolarcellsapplicationshttp://www.intechopen.com/books/optoelectronics-advanced-materials-and-devices/iii-v-multi-junction-solar-cells &FraunhoferISE
Organicsolarcell:- DSSC&Organicsolarcells
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- Instabilityandlimitationofmaximumtemperature
- Currentefficiencyisstillrelativelylowcomparewithtraditionalsolarcells
+Theylow-costmaterialsandarelessintricatetofabricate
+Perfectfor"lowdensity"applications
+Shortpaybackperiodandlowenvironmentalimpactinfabricationandoperation
+Flexibilityindesigningandstructurehttp://www.infinitypv.com/infinitypro/opv/demonstrator
HeterojunctionIntrinsicThinlayersolarcells
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• A p-type a-Si layer is deposited on a n-type c-Si wafer to form a p/n heterojunction, with an intrinsic a-Si layer in between
• On the other side of the n-type c-Si is an intrinsic and n-type a-Si layers to obtain a Back Surface Field (BSF)
• Lights is absorbed by the c-Si and photo-generated carries are diffused to the a-Si layer for collection
• Combinationofdifferent layersleads tobanddiscontinuities, resulting incarriersblocking layersatbothendsoftheinterface
• Transportofcarriersattheinterfaceisviathermionic emissionandtunneling
• Abandoffsetof0.6eVbetweena-Si:H/c-Siisfavorable
• Differenceinbandgapresultsinablocking layerfortheminoritycarriers
HeterojunctionIntrinsicThinlayersolarcells
[Seeref3] 11
+ Good stability under thermal and radiation exposure
+ Efficiency capable of exceedingc-Si (>20%)
+ Low thermal budget
+ Cheap intrinsicamorphous Si used as passivator
+ Back surface field reduces rear surface recombination
- Low production scale but high potential to exceed c-Si in future
+ Fabricating temperature about 200ºC
+MinimizedthicknessPtypea-Si:Htoreducetheabsorption
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HeterojunctionIntrinsicThinlayersolarcells
SANYOElectricCo.,Ltd.
OUTLINE
ØObjectiveofresearch
ØCurrentstatusofevaluatedPVcells
ØSimulationofHITsolarcell
ØWeighingfactors
ØFutureprospectsofHITsolarcell
ØConclusion
ØBibliography 13
SimulationparametersPC1D- PersonalComputerOneDimensional,isanumericalsimulatingsoftwareforsolarcellsdevelopedin
AustraliaattheuniversitySouthWalesofSydney.Allparameterstakenfromref[4][5]
• Devicecellarea–100cm2
• Lightsource- Onesun(AM1.5,1000W/m2)
• Frontsurface– Textured
• Exteriorfrontreflectance3%[default]
• Exteriorrearreflectance95%[default]
• Ambient temperature at 300K
• Emitter Contact Enabled
• BaseContact0.0015Ω
• Internalconductor0.3S14
SimulationparametersParameter a-Si(p) a-Si(i) c-Si(n) a-Si(n+)
Thickness(μm) 0.01 0.01 300 0.01Dielectricconstant 11.9 11.9 11.9 11.9Electronaffinity(eV) 3.9 3.9 4.05 3.9
Bandgap(eV) 1.72 1.72 1.12 1.72Electronmobility(cm2V-1s-1) 7 7 1140 7
Holemobility(cm2V-1s-1) 1 1 420 1
DopingConcentration(cm-3) 5x1019 0 1.5x1016 8.2x1019
BulkRecombination(μs) 10 0 10 10
Front-SurfaceRecombination(cm/s) 107 107 107 107
Rear-SurfaceRecombination(cm/s) 107 107 107 107
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SimulationResults
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Voc=0.7086V,Isc=3.912A,Pmax=2.333W,FF=84%, ! =23%SchematicofsimulatedcellusingPC1D
SimulationResults
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Effectofa-Si:H(i)asapassivator• Variedfrom2nm-20nm
• Efficiencydecreasesasthicknessdecreases
• Thinnerlayerofa-Si:H(i)isseentobe
effective
• Efficiencyatthickness15nmissamewhen
thecellhasnobufferlayer
• Reductionincostofcellfabrication
• suppressingrateofdegradationofminority
carriers
EffectofBackSurfaceFieldThickness• Backsurfacefieldofasolarcellreduceseffectofrear
surfacerecombinationofchargecarriesonvoltageandcurrent
• TheBSFthicknesswasvariedfrom2-12nmandthereafteritisseenthatthevariationofthickdoesn't’taffecttheoutputoftheHITcell
• Thinnerlayersofn-typea-Si:HisonlyrequiredforHITsolarcell
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SimulationResults
Thickness[nm] Voc[V]
Current[A/cm²]
Efficiency
[%]
2 0.7086 3.911 23.26
4 0.7086 3.912 23.26
8 0.7086 3.9120 23.29
10 0.7086 3.9120 23.33
12 0.7086 3.912 23.33
Cellperformanceasafunctionofthedopingconcentrationofthen-typeamorphouslayer(BSF)
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SimulationResults
Efficiency,opencircuitvoltageandshortcircuitcurrentstartedtosmoothout8.2x1019cm3
and8.2x1020 cm3
Impactofwaferc-Sithickness
• Efficiencyisstablefrom150micrometerbut
thinnerwafercouldbepronetomechanicaland
thermalstress
• Lowabsorptioncoefficientc-Sirequiresincreasein
thickness(~200μm)formorephotocurrent
generation
• Furtherincreaseofc-Sithicknessbeyond200
micrometremightnotbenecessaryandcostcould
besaved20
SimulationResults
OUTLINE
ØObjectiveofresearch
ØCurrentstatusofevaluatedPVcells
ØSimulationofHITsolarcell
ØWeighingfactors
ØFutureprospectsofHITsolarcell
ØConclusion
ØBibliography 21
Modulecostofproduction• HITsolarcellshavethepossibilityofagoodlearning
curveinthefuture(costandproductionscale)
• c-Sisolarcellsarestillexpensiveduetotheirproductionprocesses
• CIGSandCdTesolarcellsarecheaper,possibilityofhigherproductionscalebuttheyhavelowerefficiencyandalsolimitedinresource
• a-SisolarhaveahugefuturisticproductionscaleandpossibilityoflowercostperwattbutstillpronetoStaebler-Wronskieffect 22
Technology c-Si a-Si:H HIT CIGS CdTe
Cost(€/Wattpeak) 0.88-1.8 0.50-1.2 N/a ca.1.0 ca1.0
Efficiency(%)
13-19 8-11% >19.7 10-12 6-10
Basicmaterialshortage
No No No Indium Tellurium
Productionscale(MWp)
>1000 >500 900 <10 10
Life span (yr) 25 20 20-25 20 20
Thickness(µm) 150-500 100 200 1-2 10
Paybackperiod(yr) 2-4* <1 <1 n/a n/a
Lifecycle&Energyanalysisofc-Si,a-SiandHITPV• c-Si- High temperatureinproduction resultsinhugeproduction energy,moreGHGemissionandhighEPBT.Lowtemperaturecoefficientresulting tolesspowergenerationathigh temperature
• HIT- Lowtemperaturerequired inproduction processthereforelowenergyinproduction, resulting inlowEPBTandlowGHGemission.Hightemperaturestabilityaccompaniedbymorepowergeneration
• a-Si- Lowenergyinproduction, unstableunderhightemperature,lowGHGinproductionbut lowefficiencyresultsinlowpowergeneration
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PVTechnology
EnergyRequired(MJ/m2)
Energypaybackperiod(years)
GHGemission(gCO2eq./k
Wh)
Moduleconversionefficiency
(%)
Crystalline PV 5300-16,500 2-4 63 18
Thin films PV 2500 <1 34.3 11
HITPV N/A <2 N/A 19.7
AnalysisofEfficiencyforevaluatedcells
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c-Sicells-21.3- 25%HITcell-25.6%Thinfilms– 22.1-22.3%
http://www.nrel.gov/ncpv/(NationalRenewable EnergyLaboratory, Golden, CO.)
EnvironmentalIssue
• AllPVtechnologyemitGHGsandpollutantsduringfabrication
• Workersareexposedtohazardouscompoundsduringfabrication
• HITproductionprocessisn'tintricateandcomplex,thereforeworkersareexposedtolessertoxicsubstance
• HITis“greener”thancrystallinesiliconsolarcells
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PV technology Types of Potential Hazards
c-Si SiH4 fires/explosions,silicondust.Acidburns.
a-Si:H SiH4 fires/explosions,ClH3Si,FlammableH2
CdTe Cadmiumandtelluridetoxicity,carcinogenicitychemicalcompounds.
CIGS Cadmiumandseleniumtoxicity,carcinogenicitychemicalcompounds.
GaAs AsH3 toxicity,,carcinogenicitychemicalcompounds,Phosphine.
HIT SiH4 fires/explosions,silicondust,Acidburns,FlammableH2
OUTLINE
ØObjectiveofresearch
ØCurrentstatusofevaluatedPVcells
ØSimulationofHITsolarcell
ØWeighingfactors
ØFutureprospectsofHITsolarcell
ØConclusion
ØBibliography 26
FutureprospectsofHITsolarcell
• Withhighconversionefficiency,25yearslifetimeandnomaterial
shortage,HITcouldhaveexceedc-Sionmassproductionscale
• Less-expensiveandbetter-performingPVtechnologylikeHITcould
reducethelevelizedcostofelectricityofsolarenergyatarapidrate
• Betterqualitya-Si:Handc-Siresultingtohigherefficiency(>25%)
• HigherPVmarketshare(>c-Si)27
Conclusion• An-typec-Siabsorberwithp-typea-Si:Hemitter,n+-typeBSFandintrinsica-Si:Hinbetweenthelayers,couldpossiblyresulttoahighefficiencyHITsolarcell.
• HITsolarcellcouldbefabricatedatlowertemperature(~200℃)andshorterprocessingtime,unlikec-Sisolarcells.
• Withlowthermalbudget,EPBTisreduced
• Goodthermalstability,accompaniedwithhigherpowergeneration
• PossibilityofreducingofBSFthickness(ca.2-4nm)
• Efficiencyisrelatedtothea-Si:Hlayerthickness,thickerintrinsica-Si:Hlayersleadtoreductioninefficiency
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Bibliograph1. Dr. Alan Doolittle. ECE 4813: Semiconductor Device and Material
Characterization. School of Electrical and Computer Engineering GeorgiaInstitute of Technology.
2. Photovoltaics report ( June, 2016). Fraunhofer Institute for Solar Energy Systems,ISE with support of PSE AG. Pg 40. Freiburg Germany.
3. Yiming Liu, Yun Sun, Wei Liu and Jianghong Yao. (2014). Novel high-efficiencycrystalline-silicon-based compound heterojunction solar cells: HCT(heterojunction with compound thin-layer). Phys. Chem. Chem. Phys.,16, 15400-15410.
4. Manikandan .M, et al. (2015). Performance Analysis on Conversion Efficiency ofHeterojunction with Intrinsic Thin layer (HIT) Solar Cell by PC1D Simulation.Department of ECE, SRM University, Kattankulathur-603203, Tamilnadu, India.
5. NeerajDwivedi,etal.(2012).SimulationapproachforoptimizationofdevicestructureandthicknessofHITsolarcellstoachieve27%efficiency.CSIR–NetworkofInstitutesforSolarEnergy,CSIR– NationalPhysicalLaboratory,Dr.K.S.KrishnanRoad,NewDelhi110012,India. 29
Thankyouforyourtime
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