한국교통대학교전자공학과나노전자소자연구실 q 한국대학교전자공학과나노전자소자연구실태양전지연구관련일체의공정설비를다갖추고있음 도핑관련 : Spin coater, RTP, furnace 등 전극관련 : E-beam / Thermal evaporator, RF/DC sputter

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1 태양전지원리 임동건 한국교통대학교전자공학과 1

Spin coater, RTP, furnace 등 전극관련 : E-beam /

RTP 등 패시베이션층성장 : PECVD, thermal furnace 등 텍스쳐링관련 :

2 한국교통대학교전자공학과나노전자소자연구실 q 한국대학교전자공학과나노전자소자연구실태양전지연구관련일체의공정설비를다갖추고있음 도핑관련 : Spin coater, RTP, furnace 등 전극관련 : E-beam / Thermal evaporator, RF/DC sputter, Screen printer, RTP 등 패시베이션층성장 : PECVD, thermal furnace 등 텍스쳐링관련 : ICP-etcher, Mask alingner, Wet station 등 CIGS 관련 : Co-evaporator, Co-sputter, RTP, CBD 등태양전지및반도체소자관련다수의연구과제수행 결정질실리콘태양전지, CIGS 박막태양전지, TCO 등 [ 동아일보, ] 협력기업 : LG 디스플레이, 신성솔라에너지, DMS, 에버테크노, 아바코, 삼성SDI, 웅진에너지, 한화케미칼, 한국에너지기술연구원등인력현황 : 박사과정 2명, 석사과정 9명, 학부연구생 4명 ( 총 15명 ) 2

Solar simulator Semiconductor parameter analyzer Hall measurement [ 동아일보 system, 2009. 4. 21.] UV/Vis.

3 나노전자소자연구실시설현황 RTP selenization E-beam evaporator RTP CBD system RTP Mask aligner Spin coater ( 2) Diff. furnace Laser RIE PECVD Wet station ( 2) Dry oven ( 2) RF Sputter DC Sputter Oxidation furnace Co-sputter Co-evaporator Solar simulator Semiconductor parameter analyzer Hall measurement [ 동아일보 system, ] UV/Vis. Spectrophotometer 4pt probe Optical microscope Screen printer ( 2) IPCE Light soaking system 결정질실리콘태양전지공정실 CIGS 박막태양전지공정실 [ 한국교통대전자공학과나노전자소자연구실내부배치도 ] 3

4 왜태양전지가필요한가? Energy Resource Limit Combustion of Fossil Fuels Weather Change Range of Fossil Energy Carrier Uranium Natural Gas Oil Coal CO 2 Green House effect Earth warming Primary Energy Coal 27% Oil 40% Nuclear 7% Hydro 3% Natural Gas 23% Development of World Oil Demand unreacted HC Fossil combustion C m H n + no 2 NO x SO 2 + Light + H 2 O Hurricane South pole s ice thawing Smog Acid Rain 4

5 지구는앞으로도안전할것인가? [ 유가 ] [ 영화 불편한진실 ] 5

6 지구온난화의예 캐나다뮈어빙하 [ ] (Source : [ ] 6

7 지구에서사용하는에너지가부족해진다면? 7

8 3E-Trilemma 8

9 에너지에대한새로운패러다임 9

10 패러다임의변화 Environment = Money (?) 10

11 irradiation outside atmosphere 5450 (10 3 EJ/yr) 태양전지공학 500 (9%) 2060 (38%) 1310 (24%) available for absorption in lithosphere + biosphere (soil, rock, plants, etc.) conversion: absorption in 태양에서오는에너지자원은충분한가? EJ/yr (20 MW/person) absorption in hydrosphere (water) 1310 (24%) 270 (5%) human energy consumption: EJ/yr (average 2.5 kw/person; range 0.1~10 kw/person) reflection in atmosphere absorption in atmosphere reflection at surfaces 11

12 AM(Air Mass) = 1 cosq 지상에도달한태양광은어떻게 Utilizing visible light 12

13 태양전지란? 태양전지는반도체성질을이용하여빛에너지를전기에너지로변환시키는장치 p 형반도체와 n 형반도체의접합으로전력이발생됨 햇빛이반도체소자인태양전지에쏘이면전력이발생되는원리 ( 광전효과 ) 를이용 [ 태양전지구조 ] [Solar cell inventors (Gerald Pearson, Daryl Chapin and Calvin Fuller) at Bell Labs are checking a Si solar cell sample for the amount of voltage produced (1954)] 13

14 태양전지종류 by basic material and its form / (crystalline-) structure single crystalline multi crystalline Silicon crystalline amorphous + µc Si thin film CdTe Solar Cell Compound Semiconductors Chalcogenides III - V group GaAs, InP, etc. CI(G)S other Chalcopyrites GaAs Dye sensitised InP Other Concepts organic structures others others 14

희귀원소원료수급재료물성개발양산공정개발 Cd 중금속문제및 Te 부족기판재료한정대면적화제조원재료손실 Wafer 생산시원료수급및제조비용고가, 효율열화현상 대표회사 Energy Conversion Devices, Sharp, Kaneka, China Solar

15 태양전지종류별특징 태양전지종류 a-si 박막 CIS / CIGS 박막 CdTe 박막결정질실리콘 응용사례 모듈효율 6-8.5%; triple 12% 11-13% 8-10% 13-18% 장점 기술의성숙도제조비용저가턴키솔루션다양 박막태양전지최고효율제품장기신뢰성다양한기판활동타박막대비재활용가능 제조비용저가면적대비고효율 제품의안정성성숙된제반기술안정된시장성 단점 저효율초기열화문제시장축소우려 희귀원소원료수급재료물성개발양산공정개발 Cd 중금속문제및 Te 부족기판재료한정대면적화제조원재료손실 Wafer 생산시원료수급및제조비용고가, 효율열화현상 대표회사 Energy Conversion Devices, Sharp, Kaneka, China Solar AVANCIS, Solar Frontier, Nanosolar, DayStar, Miasole, Honda First solar, Antech Motech, E-Ton, Trina Solar, Suntech, Sharp, Q-Cells 출처 : International Energy Agency (IEA); photon International; CLSA Asia-Pacific Markets(2009) 15

16 태양전지동작원리 Sun light Light absorption Carrier generation Carrier separation Electric Energy Carrier collection 16

17 태양광흡수 Longl Neutral n-region E o Drift Diffusion Neutral p-region Mediuml Shortl Finger electrode l n L h Depletion region W L e l p Back electrode V oc 17

18 pn 접합이필요한이유 접합전 접합후 18

19 태양전지등가회로 The equivalent circuit of a solar cell (a) Ideal pn junction solar cell (b) Parallel and series resistances R s and R p. 19

tact and the silicon + resistance of the top and rear metal contacts e main impact of series resistance is to reduce the fill factor, although essively high values may also reduce the short-circuit

20 tact and the silicon + resistance of the top and rear metal contacts e main impact of series resistance is to reduce the fill factor, although essively high values may also reduce the short-circuit current. ies resistance does not affect the solar cell at open-circuit voltage ce the overall current flow through the solar cell, and therefore ough the series resistance is zero. wever, near the open-circuit voltage, the I-V curve is strongly cted by the series resistance. R = R + R + R + R + R + R Total MF CF E B CR 직렬저항 (Series Resistance, Rs) MR - Base & emitter resistance + contact resistance between the metal 20

21 직렬저항이효율에미치는영향 W W The series resistance broadens the I V curve and reduces the maximum available power and hence the overall efficiency of the solar cell. The example is a Si solar cell with n 1.5 and I o ma. Illumination is such that the photocurrent I ph = 10 ma. 21

22 직렬저항이효율에미치는영향 Finger electrodes on the surface of a solar cell to reduce the series resistance 22

23 Front metal R CF R MF R E R CF R SHUNT R CF R sh =8 50W, 8.0% 병렬저항이 h=12.2% R 200W,11.1% SHUNT R CR 100W,10.2% R MR 2 R CR Rear metal R MR 23

24 병렬저항이효율에미치는영향 - Significant power losses caused by the presence of a shunt resistance (R Sh ) are typically due to manufacturing defects, rather than poor solar cell design. - Low shunt resistance causes power losses in solar cells by providing an alternate current path for the light-generated current. - Such a diversion reduces the amount of current flowing through the solar cell junction and reduces the voltage from the solar cell. - The effect of a shunt resistance is particularly severe at low light levels, since there will be less light-generated current. - In addition, at lower voltages where the effective resistance of the solar cell is high, the impact of a resistance in parallel is large. - An estimate for the value of the shunt resistance of a solar cell can be determined from the slope of the I-V curve near the short-circuit current point. 24

25 직렬및병렬저항이효율에미치는영향 25

26 빛의세기에따른영향 - Changing the light intensity incident on a solar cell changes all solar cell parameters, especially short-circuit current. 26

27 온도에따른영향 - In a solar cell, the parameter most affected by an increase in temperature is the open-circuit voltage. - The open-circuit voltage decreases with temperature because of the temperature dependence of I 0. T I SC increases slightly and V OC decrease Measuring solar cell efficiency in Antarctica. Solar cells love cold sunny environments. 27

28 Comparative Advantage Region in Thin Film Solar Cell Comparative advantage region 28 * Kaneka at Intersolar 2008

29 결정질 Si 태양전지이론효율과실제효율차이 Ideal efficiency under AM1.5 conditions Voc = 800mV Jsc = 46mA/cm2 FF = 90% Eff = 33% (Assumptions) - Perfect light absorption - No SRH recombination - Operating under high injection condition in the Auger limit - One phonon limit - (Comparison) Without photon limit, the ideal current density is 42.2mA/cm 2 and short wavelength loss 30%, long wavelength loss 26%. 29

30 Efficiency Vs. Cost 30

31 고효율화를위한전략 Sun Light Sun Light Thermal Loss Front Electrode C. B. Rear Elecctrode V. B. Not absorb [Effective Light Capture] [Effective Carrier Generation] R MF n R CF R E R Shunt p R CR R MR [Effective Carrier Separation] [Effective Carrier Collection] 31

32 결정질 Si 태양전지고효율화전략 c-si HE cells Selective emitter Back contacted Enh. rear surface Enh. front texture Diffusion masking LDSE MWT EWT LFC Locally opened Etch masking Ablation PSG layer Spray-on TSV RCI Firing Masking Ablation Diffusion Diffusion Drilling Scribing Ablation Ablation 32

33 21.2 % 19.7% 고효율화기술에 18.3 % 17.1 % 16.8 % 16.5% 15.6 % 14.8 % 14.7 % 33

34 태양전지기술에따른효율 34 (Source: Progress in photovoltaics: Research and Applications, vol.16, p.62, 2008)

실리콘태양전지시장의미래는? q 폴리실리콘은 2010 년을시작으로공급과잉으로전환. 2009 년까지폴리실리콘의공급부족은결정질실리콘태양전지의가격을크게인상시킴. 폴리실리콘의공급량확대로 2010 년이후부터는공급과잉이예상됨.

35 실리콘태양전지시장의미래는? q 폴리실리콘은 2010 년을시작으로공급과잉으로전환 년까지폴리실리콘의공급부족은결정질실리콘태양전지의가격을크게인상시킴. 폴리실리콘의공급량확대로 2010 년이후부터는공급과잉이예상됨. q 폴리실리콘의가격하락으로결정질실리콘태양전지의경쟁력은크게향상. 폴리실리콘의공급과잉으로가격은지속적으로하락할것으로예상. 폴리실리콘의지속적인가격하락은결정질실리콘태양전지의경쟁력을크게향상시킴. 35 [ 폴리실리콘수요및공급전망 ] [ 폴리실리콘가격전망 ]

실리콘태양전지시장의미래는? q 결정질실리콘태양전지모듈가격의하락은가격경쟁력을크게강화시킴. 태양전지기술개발로인하여모듈가격은지속적으로낮아질것으로예상. (Yingli solar: $0.99/W, 국내업체 : $1.48/W) ß 중국은수직계열화로원가절감태양전지가격하락으로 2015 년부터 grid parity 가달성되기시작할것으로예상.

36 실리콘태양전지시장의미래는? q 결정질실리콘태양전지모듈가격의하락은가격경쟁력을크게강화시킴. 태양전지기술개발로인하여모듈가격은지속적으로낮아질것으로예상. (Yingli solar: $0.99/W, 국내업체 : $1.48/W) ß 중국은수직계열화로원가절감태양전지가격하락으로 2015 년부터 grid parity 가달성되기시작할것으로예상. q Grid parity 가달성되는시점부터태양전지의시장이급격하게성장할것으로예상. Grid parity 가달성되면태양전지시장은급격하게성장할것임. 원재료의적은매장량 (In, Te 등 ), 환경문제 (Cd 등 ), 낮은신뢰도 ( 유기물, 염료등 ) 의문제로급격한시장성장에대응할수있는태양전지는실리콘계태양전지밖에없음. [ 에너지원별발전단가비교 ] [Grid parity 예상시기 ] [ 태양전지시장전망 ] 36

37 박막태양전지시장의미래는? q 박막태양전지시장점유율은계속높아지고있음. (19.8%(2009) à 27% (2013F)) q 현재는주택용 (roof-top 구조 ) 태양전지가가장많은비중을차지하고있음. 이때효율이가장중요한요소이므로태양전지시장은결정질실리콘태양전지가주도하고있음. q 하지만향후 utility scale의태양전지시장이크게성장할것으로예상됨 q 향후태양전지는효율보다는태양전지원가가더욱중요한요소가될것임. 따라서결정질실리콘태양전지의비중은낮아지며박막태양전지의시장은성장할것으로예상 q 이때장기적인안정성과신뢰성은기본으로높은효율을가질수있다면시장을주도할수있는태양전지의가능성이매우크다고볼수있음 q 박막태양전지시장은 CIGS 박막태양전지가주도할것으로예상하였음. (a-si à CdTe à CIGS, 2020년이면박막태양전지시장의 40% 를차지할것으로예상 ) q 최근 a-si 태양전지의가격경쟁력이다시높아지면서 a-si 태양전지에대한관심이고조 q 결국가격경쟁력을먼저확보하는태양전지가시장에서살아남을가능성이높음 37

(~99%) MG-Si MG-Si supplier + SiCl 4 + H 2 or SiF 4 + NaAlH 4

38 Poly-Si 제조공정 초고순도원료실란 Si 석출공정 SiO 2 + C + HCl SiHCl 3 (TCS) TCS-Siemens MS- Siemens Bell-jar Siemens Reactor poly-si 막대형 Si (~99%) MG-Si MG-Si supplier + SiCl 4 + H 2 or SiF 4 + NaAlH 4 SiH 4 (MS) TCS-FBR MS-FBR Fluidized Bed Reactor (FBR) poly-si 그레뉼형 38

39 SC-Si 웨이퍼제조공정 39

40 MC-Si 웨이퍼제조공정 40

41 Ribbon 웨이퍼제조공정 41

42 Ribbon 웨이퍼제조공정 42

43 결정질실리콘태양전지산업구조 Silicon Feedstock, Other Materials, and Equipment Ingots and Wafers Cells Modules SiO 2 Silica Metallic Silicon (MG-Si) 98~99% Si Carbon reduction Siemens reactor Trichlorosilane (TCS) purification Fluidized Bed HCl Reactor (FBR) Poly-Si Chunk/Nugget Poly-Si granules Screen printing (metal) Anti-reflection coating Sintering (belt-furnace) pn junction Testing & sorting Cleaning & texturing wafer CZ growing Single crystal Casting Multi crystal Cell testing & tabbing Interconnection (string) lamination test 43

44 박막실리콘태양전지산업구조 Materials and Equipment Modules 44

45 태양광모듈제조공정 Glass Glass Washer EVA Sheet String Lay up Bus bar Soldering EVA Sheet A Solar Cell Cell Sorter Cell String A Back Sheet Dark I-V Check Laminator Edge Trim g Module Frame Junction Box Simulator Hi-POT Tester Clean g Pack g 45

46 46

47 결정질 Si 태양전지기술발전과정 Date Properties Design 1941 Grown in junction device Impurity segregation in recrystallized silicon melt Efficiency-fraction of 1 % grown junction n-type top contact (+) p-type rear contact -) ( 1952 He Ion bombardment junction device Efficiency ~ 1 % He Ion bombardment junction p-type 1954 First modern silicon solar cell with efficiency ~ 6 % Single crystalline silicon with p-n junction having boron diffused n-type (-) p-type (+) (+) 47

48 결정질 Si 태양전지기술발전과정 Date Properties Design top metal antireflection coating contact 1960s Space Solar Cell that remained a standard design for a decade n-type p-type rear metal contact 1973 Shallow Junction violet cell Fabricated by COSMAT Efficiency was as high as 16% P- type p + layer thin n-type layer 1974 Chemically textured nonreflecting black cell Fabricated by COSMAT Efficiency was as high as 17% textured surface p - type 48

결정질 Si 태양전지기술발전과정 Date Properties Design 1985 1990 Microgroove passivated emitter solar cell ( PESC) First

also. (Manufacturer- BP Solar) microgroove front metal contact n + p-type p + thin oxide rear metal contact

49 결정질 Si 태양전지기술발전과정 Date Properties Design Microgroove passivated emitter solar cell ( PESC) First cell with more than 20% conversion efficiency Buried contact solar cell Commercially successful for large area also. (Manufacturer- BP Solar) microgroove front metal contact n + p-type p + thin oxide rear metal contact textured front surface contact n + n ++ p-type p + plated metal in groove rear contact 49 [Buried contact solar cell]

50 결정질 Si 태양전지기술발전과정 Date Properties Design 1988 Rear point contact Solar Cell Conversion efficiency ~ 22% Commercially successful for large area also Manufacturer- Sunpower ) p + busbar rear surface oxide n + busbar n + n + n + front surface Passivated Emitter and Rear Contact (PERC) cell. Primitive type of the world s best PERL cell of UNSW Passivated Emitter and Rear Locally ( PERL) Diffused solar cell Record high silicon solar cell with efficiency 24.7% (1999 A.D.) on small area ( 2cmx2cm) inverted pyramids front metal contact n n+ p-type oxide rear contact front metal contact inverted pyramids p + n + n oxide p-si rear contact 50

51 Fabricated at Cell Type Bell Lab. Date Hoffman Electronics 1997 Stanford University UNSW COSMAT Space Cell Violet Cell First terrestrial siilcon cell UNSW PESC Black Cell Efficiency PERL PERC Back contact Cell Prope

52 World s Best Single Crystalline Si Solar Cell Size : 4cm 2 Res. (Sub.) : 1.0 Ω-cm Voc : 706mV Jsc : 43.3mA/cm 2 FF : 82.8 Eff. : 24.7% [PERL (Passivated Emitter, Rear Locally-diffused) cell] 52

53 World s Best Multi Crystalline Si Solar Cell Size : 1cm 2 (thick 99μm) Res. (Sub.) : 0.6 Ω-cm Voc : 664mV Jsc : 37.7mA/cm 2 FF : 80.9 Eff. : 20.3% 53

54 결정질 Si 태양전지양산기술 54

55 결정질 Si 태양전지양산기술 55

56 결정질 Si 태양전지양산기술 56

57 결정질 Si 태양전지양산기술 57

[ 화학 ] 과학고 R&E 결과보고서 나노입자의표면증강을이용한 태양전지의효율증가 연구기간 : ~ 연구책임자 : 김주래 ( 서울과학고물리화학과 ) 지도교사 : 참여학생 : 원승환 ( 서울과학고 2학년 ) 이윤재 ( 서울과학고 2학년 ) 임종

[ 화학 ] 과학고 R&E 결과보고서 나노입자의표면증강을이용한 태양전지의효율증가 연구기간 : 2013. 3 ~ 2013. 12 연구책임자 : 김주래 ( 서울과학고물리화학과 ) 지도교사 : 참여학생 : 원승환 ( 서울과학고 2학년 ) 이윤재 ( 서울과학고 2학년 ) 임종찬 ( 서울과학고 2학년 ) 소재원 ( 서울과학고 2학년 ) 1,.,.,.... surface