Professor N Cheung, U.C. BerkeleyLecture 26EE143 F2010Solar Cells Fabrication Technologies1•Crystalline Si Cell Technologies•Amorphous Si Cell Technologies•Thin Film Cell TechnologiesFor a comprehensive tutorial on solar cells in general, see www.udel.edu/igert/pvcdromProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F2010Global Energy Sources projectionSource: World Energy CouncilProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F20103The Growth Rate Captures the Attention Source: AMATProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F2010Solar Facts•The earth receives more energy from the sun in just one hour than the world uses in a whole year.•1% of the land today used for crops and pasture could supply the world's total energy consumption.•The Sun provides 1020 Watts/meter² peak power at sea-levelCell efficiency of 10% translates to ~100W/meter2Professor N Cheung, U.C. BerkeleyLecture 26EE143 F2010Commonly Known Solar Cell MaterialsProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F2010FraunhoferProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F20107Beside efficiency, there are other considerations for ultilizationProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F2010Projected Module CostProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F20109Energy ContentEG silicon ~ 200 kWh/kgSolar Grade Si ~ 50kWh/kgMG silicon ~ 20kWh/kg Richard Corkish ,Solar Progress, (1997)Energy Payback time Monocrystalline Si cell ~ 4 yearsPolycrystalline Si cell 1.6 to 2.7 yearsAmorphous Si cell 0.9 to 1.6 years.Professor N Cheung, U.C. BerkeleyLecture 26EE143 F201010Crystalline SiliconAmorphous SiliconCIGSCdTeOrganicConversion Efficiency13-18%5-10%10-12%10.5%5%Current cost per Watt*$2.5-3.5$2-2.5$0.6 (predict)$1.3<$1 (predict)Material ShortageNoSilaneIndiumTe(?)NoToxic SubstanceNANACadmiumSeleniumCadmiumTelluriumNAReliabilityExcellentFairGoodGoodPoorCompany in the fieldSuntech, SunPowerAMAT, DupontNanosolar, SolyndraFirst SolarKonarkaComparison of commercial PVProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F2010•Crystalline solar cells are usually wafers, about 0.3 mm thick, sawn from Si ingot• 15% efficiency cells deliver 15 to 60 W/m² or 0.45-1.35 kWh/m²/day (annual day and night average) in North America Si Crystalline Solar cells are just large area semiconductor diodesProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F201012From Ingot to ModuleProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F201013From Ingot to Module (cont.)Professor N Cheung, U.C. BerkeleyLecture 26EE143 F201014From Sand to SiliconProcess generates four tons of silicon tetrachloride liquid waste for each ton of polysilicon produced.Professor N Cheung, U.C. BerkeleyLecture 26EE143 F201015Professor N Cheung, U.C. BerkeleyLecture 26EE143 F201016Professor N Cheung, U.C. BerkeleyLecture 26EE143 F201017Minimize Kerf LossProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F201018Generic Crystalline Si Cell ProcessingAl-Ag paste* Al-Ag fuses through SiNx to form ohmic contactProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F201019Backside Al contact(BSF= back surface field p+ layer)Professor N Cheung, U.C. BerkeleyLecture 26EE143 F201020Max T =950CBelt FurnaceProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F201050 MW fab cell line. (Source: Applied Materials)Professor N Cheung, U.C. BerkeleyLecture 26EE143 F201022Professor N Cheung, U.C. BerkeleyLecture 26EE143 F201023Professor N Cheung, U.C. BerkeleyLecture 26EE143 F201024Professor N Cheung, U.C. BerkeleyLecture 26EE143 F201025Antireflection Coating MaterialsProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F201026Diagnosis of Crystalline-Silicon Solar- Cells Utilizing Electroluminescence: save production costs by sorting out defective solar-cells in an early stageProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F201027Module PackagingSource: Spire CorpProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F2010Crystalline Si on Glass (CSG) Solar Cell* All fabrication done with Laser processing and low-temperature PECVDProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F201029Sliver CellA wafer (assume 150mm diameter) configured as a conventional solar cell has an area of 177cm2. However, the same wafer, when processed to produce Sliver® cells, can be used to cover up to 5,000 cm2 of module area, which is 30 times better than for conventional technology.Professor N Cheung, U.C. BerkeleyLecture 26EE143 F2010Both silicon and thin-film PV solutions require a reduction in cost/watt. (Source: Applied Materials)Motivation for amorphous Si CellProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F2010Rigid and Flexible a-Si Solar CellsCell efficiency, h = Voc× Jsc× FFPini- a-Si:HTextured TCOZnOp- a-SiC:Hn- a-Si:H30% T Ag Glass / TCO / p / i / n / Ag SS / ZnO / p / i / n /AgOpaque (SS/Kapton)GlassVoc Doped layersJsc i-layer defect density Light trappingFF i-layer defect density InterfacesProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F201032Amorphous Si DepositionProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F201033Amorphous Si DepositionProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F201034Source: ULVAC Solara-Si Cell ManufacturingProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F201035Source: AMATConceptual a-Si Cell FabProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F2010Professor N Cheung, U.C. BerkeleyLecture 26EE143 F201037CIGS Solar CellsProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F201038Professor N Cheung, U.C. BerkeleyLecture 26EE143 F201039Source: pmc.org.twCIGS ManufacturingProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F201040Professor N Cheung, U.C. BerkeleyLecture 26EE143 F201041Professor N Cheung, U.C. BerkeleyLecture 26EE143 F201042Professor N Cheung, U.C. BerkeleyLecture 26EE143 F201043Source: Ascent SolarRoll-to-Roll ManufacturingProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F201044Professor N Cheung, U.C. BerkeleyLecture 26EE143 F201045Needs MBE , MOCVD, or Layer TransferProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F2010Technology Evolutionc-Sithin film"New Concepts"05001000150020002500300035000204060801001201402002 2005 2010 2015 2020 2025 2030MWGW30%p.a.25%p.a.46RENEWABLE ENERGY FOR EUROPE - RESEARCH IN ACTIONProfessor N Cheung, U.C. BerkeleyLecture 26EE143 F2010Q: What are the major differences between PV fabrication and IC/MEMS fabrication ?•Patterning (alignment, size control) •Doping •Contact Formation•Metallization•PlanarizationQ: What
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