薄膜太阳能电池(thin film solar cell)课件

1、第八章 薄膜太阳能电池授课教师：黄俊杰薄膜太阳能电池的种类非晶硅(Amorphus Silicon, a-Si)微晶硅(Nanocrystalline Silicon，nc-Si，or Microcrystalline Silicon，uc-Si)CIS/CIGS(铜铟硒化物)CdTe(碲化镉)GaAs Multijuction(多接面砷化镓)色素敏化染料(Dye-Sensitized Solar Cell)有机导电高分子(Organic/polymer solar cells)太阳能电池市场现况太阳能电池效演进非晶硅(Amorphus Silicon, a-Si) 数据源：BP 2002、W

2、orld Nuclear Association是发展最完整的薄膜式太阳能电池。其结构通常为p-i-n（或n-i-p）偶及型式，p层跟n层主要座为建立内部电场，I层则由非晶系硅构成。非晶硅的优点在于对于可见光谱的吸光能力很强，而且利用溅镀或是化学气相沉积方式生成薄膜的生产方式成熟且成本低廉，材料成本相对于其他化合物半导体材料也便宜许多；不过缺点则有转换效率低(约57%)，以及会产生严重的光劣化现象的问题，因此无法打入太阳能发电市场，而多应用于小功率的消费性电子产品市场。不过在新一代的非晶硅多接面太阳能电池(MultijuctionCell)已经能够大幅改善纯非晶硅太阳电池的缺点，转换效率可提升

3、到68%，使用寿命也获得提升。未在具有成本低廉的优势之下，仍将是未薄膜太阳能电池的主流之一。CIS/CIGS(铜铟硒化物)CIS(CopperIndiumDiselenide)或是CIGS(CopperIndiumGalliumDiselenide)都属于化合物半导体。这两种材料的吸光(光谱)范围很广，而且稳定性也相当好。转换效率方面，若是利用聚光装置的辅助，目前转换效率已经可达30%，标准环境测试下最高也已经可达到19.5%，足以媲美单晶硅太阳电池的最佳转换效率。在大面积制程上，采用软性塑料基板的最佳转换效率也已经达到14.1%。由于稳定性和转换效率都已经相当优异，因此被视为是未最有发展潜力

4、的薄膜太阳能电池种类之一。CdTe(碲化镉)CdTe同样属于化合物半导体，电池转换效率也不差：若使用耐高温(600C)的硼玻璃作为基板转换效率可达16%，而使用不耐高温但是成本较低的钠玻璃做基板也可达到12%的转换效率，转换效率远优于非晶硅材料。此外，CdTe是二元化合物，在薄膜制程上远较CIS或CIGS容易控制，再加上可应用多种快速成膜技术(如蒸镀法)，模块化生产容易，因此容易应用于大面积建材，目前已经有商业化产品在市场营销，转换效率约11%。不过，虽然CdTe技术有以上优点，但是因为镉已经是各国管制的高污染性重金属，因此此种材料技术未发展前景仍有阴影存在。染料敏化染料(Dye-Sensit

5、ized Solar Cell)染料敏化感染料电池是太阳能电池中相当新颖的技术，产品是由透明导电基板、二氧化钛(TiO2)奈米微粒薄膜、染料(光敏化剂)、电解质和ITO电极所组成。此种太阳能电池的优点在于二氧化钛和染料的材料成本都相对便宜，又可以利用印刷的方法大量制造，基板材料也可更多元化。不过目前主要缺点一是在于转换效率仍然相当低(平均约在78%，实验室产品可达10%)，且在UV照射和高热下会出现严重的光劣化现象，二是在于封装过程较为困难(主要是因为其中的电解质的影响)，因此目前仍然是以实验室产品为主。然而，基于其低廉成本以及广泛应用层面的吸引力，多家实验机构仍然在积极进行技术的突破。有机导

6、电高分子(Organic/polymer solar cells)有机导电高分子太阳能电池是直接利用有机高分子半导体薄膜(通常厚约为100nm)作为感光和发电材料。此种技术共有两大优点，一在于薄膜制程容易(可用喷墨、浸泡涂布等方式)，而且可利用化学合成技术改变分子结构，以提升效率，另一优点是采用软性塑料作为基板材料，因此质轻，且具有高的可挠性。目前市面上已经有多家公司推出产品，应用在可携式电子产品如NB、PDA的户外充电上面，市场领导者则是美国Konarka公司。不过，由于转换效率过低(约45%)的最大缺点，因此此种太阳能电池的未发展市场应该是结合电子产品的整合性应用，而非大规模的太阳能发电。

7、非晶硅薄膜太阳电池构造Need of raw materialThin-film solar cells非晶硅薄膜太阳电池制造程(玻璃基材)非晶硅薄膜太阳电池制造程(玻璃基材)Thin film Si:H challengesIncreasing deposition rate (from 0.1 nm/s to 10 nm/s!), including compatible doped layersEnhance the Isc (absorption, light trapping)Improving stabilized device performanceUnderstanding f

8、undamental physics: low Voc, shunt behavior, light-induced defect creation非晶硅薄膜太阳电池“Amorphous Si:H Thin-film Solar Cell”UniSolar and薄膜太阳能电池 CIGS薄膜电池此型有种：一种含铜铟硒三元素（简称CISe），一种含铜铟镓硒四元素（简称CIGS）。由于其高光电效及低材成本，被许多人看好。在实验室完成的CIGS光电池，光电效最高可达约19.88，就模块而言，最高亦可达约13(CISe约10%)。CIGS随着铟镓含的同，其光吸收范围可从1.02ev至1.68ev，此项

9、特征可加以用于多层堆栈模块，已近一步提升电池组织效能。此外由于高吸光效（104105-1），所需光电材厚需超过1m，99以上的光子均可被吸收，因此一般粗估产制造时，所需半导体原物可能仅只US$0.03/W。薄膜太阳能电池 CIGS薄膜电池CIGS太阳能电池组件结构演进CIGS太阳能电池组件制作程CIGS太阳能电池-真空制程真空涂布制程- Co-evaporation真空涂布制程- SputteringCIGS太阳能电池-非真空制程非真空涂布制程- electrodeposition非真空涂布制程-Metal Oxide InkCIS薄膜太阳电池“Copper Indium Diselenide

10、 Thin-film Solar Cell ”245-kW rooftop, thin-film CIS-based solar electric array, Camarillo, California (Shell Solar Industries.)85-kW thin-film CIS-based BIPV facade, North Wales, UK结论各型太阳能电池的市场需求将与日遽增，且各技术皆以低成本和提高光电转换效为研究方向。其中又以薄膜太阳能电池为现阶段最具有取代硅晶太阳能电池的可能。薄膜太阳电池中，CIGS是目前具有最高效的电池之一。现阶段CIGS电池主要产技术仍以真空

11、制程技术为主，但难以克服大面积及低成本的问题。 CIGS非真空制程技术虽具有低成本以及提高材使用的优点，但各方式具有难以克服的关键问题皆仍待解决。如CIGS晶成长等。结瓶颈CIGS薄膜太阳能电池虽具有高效、低成本、大面积与可挠性等潜优势，但还有许多需要克服的问题接踵而：制程复杂、技术选择百家争鸣，且供应相当分歧，各站并无制式化设备放大制程之均质性佳，变化大 dopant ratio thin window layer Low Voc resulting in increased area loss系统化的研究与实验据十分缺乏许多关键点无定，如：组成成分、结构、晶界、各层间之接口等关键原的缺乏

12、铟元素也是一项潜在隐忧，铟的天然蕴藏相当有限，国外曾计算，如以效10的电池计算，人如全面使用CIGS光电池发电供应能源，可能只有光景可，铟的天然蕴藏相当有限，国外曾计算，如以效10的电池计算，人如全面使用CIGS光电池发电供应能源，可能只有光景地热CdTe Film DepositionCdTe Film DepositionCdTe Film DepositionRooftopCdTe薄膜太阳电池“Cadmium TellurideThin-film Solar Cell”Katzenbach Juwi Memmingen SAGSAGFirst Solar -CdTe RooftopC-S

13、i Technology in Historic Perspective全球PV前十大厂商台湾太阳光电产业链分布概况太阳光电产值预期达成规模光电高分子太阳能电池特征发展不久原理:利用不同氧化还原型聚合物的不同氧化还原位势,在导电材料(电极)表面进行多层复合,外层聚合物的还原电为较高,电子转移方向只能由内层向外层转移;另一电极正好相反奈米晶色素增感solar cellDSSC进展Why organic solar cell? Ease of fabrication for large area from solutionTransparentConformal and flexibleLow c

14、ost of manufacturingDye-Sensitized Solar CellMechanisms of the DSSCh :photon absorptiona :electron injectionb :recombinationc : e- transport and collection at conducting substrate d :I- oxidatione :I3- reductionf :ion transportBasic mechanisms in a DSSCI/I3- redox electrolytedyehTiO2TCOCounter elect

15、rodeabcdef2e- + I33I-3I-I3- + 2e-E-An Introduction to its Principle, Materials, Processes, and Recent R&DsDye-sensitized Solar Cell(DSSC):Principle ofDye-Sensitized Solar cellsDye-Sensitized Solar CellLow photocurrent could be the result ofInefficient light harvesting by the dyeInefficient charge in

16、jection into TiO2Inefficient collection of injection electronGratzel, Nature, 2001Special Features of a DSSCSemiconductor not excited directlyPhoto carrier generation & transportation arewell separated the probability of recombination can be drastically reduced.Positive charge transportvia ion trans

17、port in the electrolyte, rather than hole conditionNo electric field, electron transfer has been described as diffusionJn= nnEcb+ q DnnNanoparticle structureTCOCounter electrodeTiO2/ dye / electrolyte(I-/I3-)glasse-0Performance of Photovoltaic and Dye-sensitized Solar CellsType of cellEfficiency %(c

18、ell)Efficiency %(module)Research and technology needsCrystalline silicon2410-15Higher production yields, lowering of cost and energy contentMulti-crystalline silicon189-12Lower manufacturing cost and complexityAmorphous silicon137Lower production costs, increase production volume and stabilityDye-se

19、nsitized nano-structured materials10-117Improve efficiency and high-temperature stability, scale up production-Their functions, principles, characteristics, materials, processes, and recent R&DsPart II:Major Components in a DSSC The TCO Electrode -one of the major components in a DSSC Role of the TC

20、O electrode in a DSSCElectronstransportation and collectionCharacteristicsHightransmittance in visible region()Highelectrical conductivity()Thermal endurance ()Corrosion resistanceEnergy level not higher than nanoparticle oxide() present the issue still for improvinge-ITRCommon Materials and Process

21、es of the TCO Electrodes Materials:ITO, ZnS, ZnO, SnO2(energy gap higher than photo energy in visible region)Processes:Sputtering depositionPlasma ion assisted depositionRef (3)Recent R&Ds of TCO Electrode in DSSCMethod improvingContentsEvaluationRef.Design*Oxide/metal/oxide structure1/ tot= 2/ oxid

22、e+ 1/ metal Ref.(465)Material* TiO2 replace ITO* AgCu replace Ag as metal interlayer Thermal enduranceRe. f(7)Ref. (8)Processes*Heat treatment*PIAD ; TAvoid high tempRef. (9) Ref. (10)Analysis*Multi-layer combination appropriate arrangement of the n & t of each layerR ; TOptic simulationRef. (11) Re

23、f. (12)Incident =Reflection + Transmittance +AbsorptionPassage of Light Through a Material related torefractive index,thickness, particle sizeDepend onEgParticle size effectInterference effectdSubstraten1nsn0Nano-material transmit lightMicro-material scatter lightRef (14)Ref (13)dyedye -one of the m

24、ajor components in a DSSC Role of dye in a DSSCPhotoexciting & injecting electrons into the conduction band of the oxide CharacteristicsAbsorb all light below 900nm ()Molecular dispersion in nanostructure oxide ()Carry attachment group(eg. carboxylate or phosphonate) tofirmly graft to the oxide surf

25、aceThe Energy level ofexcited state higher than conduction band of oxide The redox potential sufficient high to be regenerated via electron from the electrolyteSustain high cycle usageTiO2Ru2+Ru2+*Ru3+e-e-hCommon Materials of the DyeGeneral structure: ML2X2( L: 2.2-ipyridyl-4,4-dicarboxylic;M: Ru or

26、 Os;X: halide,-CN,-SCN )N3Absorption Spectrum of N3 and dark grayDark grayAM1.5 solar spectrum400500600700800900nmA00.51.01.52.0N3Dark grayRef (14)Recent R&Ds of Dye in DSSCMethod improvingContentsEvaluationRef.Design*Mix different dyes Broadband absorptionRef. (15)Material*Different types of ligand

27、Explore:e- donation process, charge recombination, sensitizer regenerationRef. (16)Oxide Film-one of the major components in a DSSCRole of the oxide in a DSSCReceive electrons from the dyeEfficient transport electrons in the media CharacteristicsUltra fine structure(nm-crystal, mesoporous) interconn

28、ected ()Good electrical conduction properties ()Conduction band edge is more negative than HUMO of the dye ultra fine structure enable.TiO2 nanoparticlesRef (17)Ref (3)IPCE%001000.15300800nm300800nmSingle crystal anataseNanocrystal anataseCommon Materials and Processes of the Oxide filmMaterial:TiO2

29、(cheap, non-toxic), ZnO, Fe2O3, Nb2O5, WO3, Ta2O5, CdS, CdSeCommon processes:TiO2filmTiO2particles (Finely divided monodispersed colloidal)Coating,sinteringTi saultProcess parameters:Precursor chemistryHydrothermal growth TempBinder additionSintering conditionControl: hydrolysis and condensation kin

30、eticsFactors influence properties:Material contentChemical compositionStructureSurface morphologyGrain size, porosity pore size distributionCrystalline form (anatase,rutile.)Hydrolysissolvent+binder(1-20m)Electron Transport in the DSSC- An important factor affecting IPCEDe in the porous film De in t

31、he bulk crystalMulti-trapping model: electron transport is mediated by the conduction band and is interrupted by trapping.The traps could be formed byoxygen defects,amorphous layer on the particle surface,chemical surrounding, andlattice mismatch at boundaries.Injection electrons are slow down by tr

32、apping at the surface of the particle andmay back reaction through combination with I3- iron.Ref (18)Recent R&Ds of the Oxide Film in DSSCMethod improvingContentsEvaluationRef.Design & process*Nanocrystallite(TiO2,SnO2, ZnO.) coated with the shells of material(Al2O3,MgO, ZnO)*Column ZnO film (struct

33、ure scale 100-500nm ) -electrodeposition, non- equilibrium growth on wurtzite crystal*addition of larger particle TiO2Voc; IPCEscatteringscattering( optical path length)Ref. (19)Ref. (20)Ref. (21)Analysis*SPV(surface photo voltage measurement)*Decay kinetics(nanosecond transient absorption)Detect electron injection processRef. (22)Ref. (23)Band positions of semiconductorsThe Electrolyte -o