柔性电子器件与制造第23节柔性太阳能电池

FlexibleElectronicsDevice&ManufacturingFlexibleElectronicsResearchCenterSchoolofMechanicalScienceandEngineeringHuazhongUniversityofScienceandTechnologyChapter2.3FlexiblesolarcellYongAnHuang,Ph.DOutline21.Solarcell2.Workingprinciple3.P-NJunctionsolarcell4.Dye-sensitizedsolarcellSolaratthecostofcoal3Solarradiation(energy)receivedwithinonehourontheearthissufficienttomeetthetotalenergydemandoftheworldformorethanoneyear!1Hour=1Year？ConvertingtheenergyofsunlightintoaneasilyusableformisoneofthemostattractivesolutionsbecausedailysunshinedeliversenergytotheEarththatis10,000timeslargerthanpresentworldenergyconsumption.GlobalMeanSolarIrradiance4Solarelectricity•Clean•Environmentallysafe•Silent•Nomovingparts•Pleasingappearance(doesnotdestroylandscape)RenewableEnergySource•FreefrompoliticalandgeographicalinfluenceSolarcell:DirectlyconvertslightintoelectricityHydropowerstationVsPVstation5ThreeGorgeshydroelectricpowerstationConservativeprojectionsputworldwideannualcapacityat200GWin2020(capacityincreaseofabout17%peryear);othersestimateasmuchas300GWin2025(IEA2009,GreenTech2011).910010kWh？WhatisaSolarCell?6AstructurethatconvertssolarenergydirectlytoDCelectricenergy.–Itsuppliesavoltageandacurrenttoaresistiveload(light,battery,motor).–Power=CurrentxVoltage=Current2xR=Voltage2/RItislikeabatterybecauseitsuppliesDCpower.Itisnotlikeabatterybecausethevoltagesuppliedbythecellchangeswithchangesintheresistanceoftheload.Flat-plateglassracksystemWhatisaflexibleSolarCell?7SolarIntegratedTechnologies81MegawattLandfillApplication,MalagrottaItaly.−Flexiblepanelsaccommodateslandfillsettling−Deployableon„new‟landfillsandslopes−Noextracostsforflat-plateglassrackingsystem:rails,ballastcement,clips,etc.−Flexible,Lightweight,NoRacksneededvehicleUnmannedplaneaerospaceRoofFlexiblesolarcellsforclothing9PrototypeofawinteroutdoorjacketwithiPV.−ThisjacketwasdevelopedbyMaierSports,withsupportfromthepartnersintheGermanSOLARTEXproject.−ItcomprisesnineamorphousSisolarmodulesfromAkzoNobelwithamaximumpoweroutputof2.5Wunderfullsun.CourtesyofMaierSportsFlexiblesolarcellsforclothing10ExamplesofSOLARTEXprototypesfordifferentapplications.−TEMPEXjacketbrightphotovoltaic-poweredwarninglightssupplementthebuilt-inpassivesafetyfeatures,e.g.streetconstructionworkers.−Usingphotovoltaicpowerharvestedduringtheday,light-emittingdiodesenhancethevisibilityofchildrenatnightinthisKANZcoat.FlexibleSolarCell11Solarsailcanreach2%ofvelocityoflight.Thepowerisgotfromsolar.Sotheultra-flexiblesolarcellisveryimportantandenabletechnology.ThedeviceislaunchedbyUSA,butitispitythatthesolarsailisfailure.Howmanykindsofsolarcell12Flexiblesolarcells13ClassificationbasedonMaterials:─Monocrystalline/polycrystalline/amorphoussilicon;─Compoundsemiconductorsolarcell(cadmiumsulfide-CdS;galliumarsenide-GaAs)─Organicsolarcell─DyesensitizationsolarcellClassificationbasedonStructures:─SchottkyBarrierCell─p-nJunctions─DyesensitizationsolarcellSolarCells:ThePhotoelectricEffect14Thebasicprincipleofphotovoltaics–thebranchofsolidstatephysicswhichhasafocusofturninglightintoelectricalenergyItisapropertyofcertainmaterialswherephotonsoflightareabsorbedandtheenergycauseselectronstobeknockedlooseThosematerialsarereferredtoassemiconductorsSemiconductorscanbenaturalorcreatedthrough“doping”whereimpuritiesareaddedtogivemoreorlesselectronsTwokindsofsemiconductorsusedforasinglesolarcells─APositiveP-type(ElectronPoor)─ANegativeN-type(ElectronRich)HowSolarPVsWork15TocompletethePVmodule,severallayersareadded.─A-CoverGlass─B-AntireflectiveCoating─C-ContactGrid─D-N-typeSilicon─E-P-typeSilicon─F-BackContactPolycrystallinecellsareslightlylessefficientthanmonocrystallinesolarcells,butarecheapertomanufactureinwaferform.HereisanexampleofhowahomecanbewiredtorunonSolarPVpowerp-nJunctions16p-njunctionsarecreatedfromthecontactofp-typeandn-typesemiconductors.Priortocontact,EFishigheronthenside.Uponcontact,electronsflowfromthensidetothepside,untilEFisconstantacrosstheinterface.Anelectricpotential(ΔV)developsacrosstheinterface,andraisestheenergyonthepsideashigherenergyorbitalsarefilled(ΔE=-eΔV).P-NJunction17TheelectricpotentialbarrierbetweenthetwosemiconductorsofasolarcellCreatesalowresistancepathforexcitedelectronstoflowthrough“Loose”electronsflowfromtherichendtothepooronecreatingadirectcurrentThisiscalledthephotovoltaiceffectandexplainswhythetruenameforsolarcellsarePVcellsPhotogenerationofChargeCarriers18Photonscontactingthesemiconductorcaneither:─Passthroughthematerial(lowenergyphotons).─Beabsorbedbythesemiconductorandexciteanelectrontoahigherenergystate(highenergyphotons).─Bereflectedoffthesurface.Theminimumphotonenergyrequiredtocreateanexciton(electron-holepair)isthebandgapenergyofthematerial.PhotogenerationofChargeCarriers19MuchofthesolarradiationreachingEarthconsistsofphotonswithenergiesmuchgreaterthanthebandgapsoftypicalsemiconductors.Whenhigherenergyphotonsareabsorbed,electronsareexcitedfurtherintotheconductionband.Butthedifferenceinenergybetweenthe