결정질 실리콘 태양전지의 제조기술 및고효율화 개발현황

2011 Solar & Energy 기술교육세미나

한화케미칼 중앙연구소솔라연구센터

趙 在 億

jecho@hanwha.co.kr

2011. 3. 22

PV Cell Project TeamHanwha Chemical R&D Center

태양광 발전 Peak 부하 저감효과

독일의 PV 발전설비용량: 8.3GW(As of 2010]

한국 PV: 299.8MW (08,12)

목 차

1

2

3

4

태양전지 기본개념

Si 태양전지 산업현황

Si 태양전지의 고효율 전개과정

상업화 기술적 이슈

Beyond Grid-Parity

5 상업화 고효율 셀

6 차세대 실리콘 태양전지

7 Beyond SQ Limit

PN-Junction

1. 태양전지 종류 및 Status

Beyond Grid-Parity

c-Si

Advanced Si

(고효율)

This-Film

CPV

DSSCOPV

R & D Demonstration MarketEntry

MarketPenetration

MarketSaturation

Mono & multiconventional cell

Ribbon

HIT

IBC

MWT

EWT

OPV

DSSC

Low-X Concentrator

a-Si

CdTe

a-Si/-Si

CIGS

High-X Concentrator

Source: Modified From “Renewable Energy Technologies”, Lisa Frantzis, Navigant Consulting, Inc.(2005/2006)

태양전지란?

1. 태양전지 기본개념

Beyond Grid-Parity

태양전지 (Photovoltaic cell/solar cell):태양 에너지를 전기 에너지로 변환할 수 있는 장치로 일종의 에너지 변환기

Photon AbsorptionCharge SeparationCharge Transport

(carrier 이동을 위한 driving force 필요 –1개 이상의 electric field: pn junction, BSF)

Cell 효율: light absorption, impurity (carrier life time), recombination, mobility, resistance,

PN-Junction: Si 태양전지의 핵심원리 (전하분리)

1. 태양전지 기본개념

Beyond Grid-Parity

Built in potential: 0.6 to 0.7 volts.

It varies with doping levels and temperature

potential barrier or potential hill.

pre-existing electric field associated withthe p-n junction in thermal equilibrium

다수 캐리어:hole 다수 캐리어:전자

One pn-junction Si 태양전지의 최고효율

1. 태양전지 기본개념

Beyond Grid-Parity

W Shockley and HJ Queisser, J Appl Phys 32, pp. 510-519, (1961)

Color eV nm

1.10 1,100

Red 1.77 700

Orange 2.00 620

Yellow 2.14 580

Green 2.34 530

Blue 2.64 470

Violet 2.95 420

c-Si SQ limit: 29%

초고효율의 관건: 태양광 스페트럼의 효율적 사용 (Tandem Structure)

에너지밴드 수 셀효율 (1 sun)

1 37

2 50

3 56

36 72

문제는 적당한 band gap material과 공정 cost

Band gap 조절이 가능한 태양전지는 화합물 반도체 태양전지

화합물반도체 이론적 셀 효율

Beyond Grid-Parity

c-Si

Maximization of

Light absorption(Isc)

Charge separation

(Voc, Isc)

Minimization of

Serial Resistance(FF)

Surface texturing

Antireflection coating

Back Reflector

Carrier’s lifetime depends

on the wafer’s crystal

matrix defects and purity

(Bulk & Surface)

Use of pure wafers

mono C-Si > multi C-Si >

Ribbon Si > UMG-Si

(High purity high cost)

Impurity removing tech.

-wafer gettering

Passivation: removing

broken bond (-Si--Si-H)

(bulk & surface)

(박막코팅: method, 재료)

PV Cell is a electric

device.

Design of low serial

resistance

Good ohomic contact

-low contact resistance

-high

conductivity

(Printing:SP,

plating, depo)

태양전지의 효율 증대 연구는 Isc, Voc, FF 증대에 초점

1. 태양전지 기본개념

Loss from-incident light (3.6%)-recombination (7.34%)-resistive

Source: A generic solar cell has multiple loss mechanisms

c-Si Loss Mechanism:

recombination > optic

11

Multicrystalline Silicon

Monocrystalline

Silicon

SYSTEM

Beyond Grid-Parity

1. 태양전지 기본개념

Si 태양전지 산업 Value Chain

PV Cell 제조공정

1. 태양전지 기본개념

Beyond Grid-Parity

효율측정 및 분류

Solar Energy: Spectrum & Air Mass

1. 태양전지 기본개념

Beyond Grid-Parity

1,360W/m2

1,000W/m2

태양전지의 효율은 주로 AM1.5 조건하에서 측정

-자외선(3%)-가시광선(43%)-적외선(54%)

-Ozone 층이 UV 차단

-천연의 태양광은 지역, 계절, 시간에 따라스펙트럼이 변한다.

참고: 1366 Technologies

태양전지 효율(%) = 입사광량 (W)

[ 단락전류(Isc) 개방전압 (Voc) 충실도(FF) ] (W)

Ex) 4W 출력 다결정 , 4W/24.336W 16.4% 효율

고효율 Isc, Voc , FF

광량

결함 (표면 >>> bulk)온도

저항

1. 태양전지 기본개념

Solar cell efficiency records as a function of cell area. Larger cells and modules tend to have a lower efficiency.

Definitions of Area셀효율에 중요, 특히 작은셀.

Total area (t). The total area of the device including the frame.

Aperture area (ap). The device is masked so that the illuminated area is smaller than the total cell or module area, but all essential components of the device such as busbars, fingers and interconnects lie within the masked area.

Designated illumination area (da).In this case, the cell or module is masked to an area smaller than the total device area, but major cell or module components lie outside the masked area. For example, for a concentrator cell, the cell busbars would lie outside of the area designed for illumination and this area classification would be the most appropriate.

1. 태양전지 기본개념

☞ 셀 효율 : 광조사 영역 및 면적크기에 의존

Beyond Grid-Parity

Technology: Cell Efficiencies

R&D:cSi=11%/22Yr

(0.5%/Yr)

Industrial :(0.25%/Yr >)

HCPV 1%/Yr

SQ-limit: ~29%

1. 태양전지 기본개념

Efficiency depends on wafers and fabrication method.

Rib

bon

Cz,

단결

정S

i

다결

정S

i

가격

, 효

율

Wafer 종류

UM

G-S

i

후면

전극

(IB

C)

HIT

Cell

(결정

질/박

막)

Sta

ndard

C

ell

Cell Architecture

Co

st,

효율

PE

RL

(Worl

d R

ecord

)

Technolo

gy

Mate

rials

Fz,

Cz S

i(N

-ty

pe)

Premium Market: Sunpower, SanyoAverage: MostEconomy Market: Canadian Solar (UMG)

고효율 cell

Fz,

단결

정S

i(N

-ty

pe)

후면

전극

(BC

SC

)

HIT

Cell

(결정

질/박

막)

Fz,

단결

정S

i(N

-ty

pe) S

tan

dard

C

ell

다결

정S

i

Sta

ndard

C

ell

UMG-Si

Cell

효율

> 20%

15~18%

15~16%

Sta

ndard

C

ell

단결

정S

i

16~19%

Beyond Grid-Parity

1. 태양전지 기본개념

Timing of efficiency improvements difficult to predict

By 2015: Standard c-Si: ~16.5% Super mono c-Si: ~21.5% CdTe: 12.5-13% CIGS: 13-14% 1-j a-Si: 8.5-9% Tandem Si: 11-11.5%

Source: Greentech Media Research, in SPI 2010, Oct 11 2010

c-SI 태양전지 상업용 모듈효율

1. 태양전지 기본개념

Keeping cost down & Raising cell efficiency is the key Research Goals.

PV system price (Low Material & manufacturing cost)

Cell Efficiency

(more electricity)

Grid Parity(Cost of PV electricity is equal to or

cheaper than conventional electricity)

2. Si 태양전지 산업현황

※ 연료비만 반영한 단가임 (주의요함), 발전기별 정격용량 출력기준 원별 가중평균값임

Carbon tax

The levelized cost of PV electricity could fall to ~ 6¢/kWh by 2015

Most conventional base load power generation ($0.04-$0.08 per kwh), 우리나라 ~6¢/kWh

Incentive

PV industry growth, 1978-2010.

PV technology shares, 2009-2010.

Photovoltaics Worldby Paula Mints, Navigant ConsultingFebruary 22, 2011

성장률: 결정질 (103%), 박막(54%)점유율: 박막 17% 13%로 4% 감소

단결정: 35% 42% (고효율 수요증가)다결정: 46% 43%

☞ 2011년 20GW 이상 (누적 설치량 60GW)☞ 2013년 누적 설치량 100GW 돌파 예상

Source: Professor Emanuel Sachs at MIT

Module price $1/W6 cent/kWh

Phase I Phase II Phase III

Learning curve: 18~20% price reduction upon every doubling of cumulative installed Wp

누적 설치량과 Grid Parity 예측

“Global Solar Energy Outlook”Grid Parity by 2013 (June 2010)

Thin film low efficiency

Area penalty (land/roof, hardware)

Historically, 1% 효율 4% BOS

효율 (%) 가격

c-Si 14.5 1.5

Cd-Te 10.5 1.3

c-Si/a-Si 10.5 1.3

a-Si 6.5 1.0

Source: Photon International, Feb 2011

모듈가격 비교 (결정질 vs. 박막)

Source: Solar Annual 2007 (Photon Consulting)

1GW=1,000MW

결정질 vs. 박막 가격 추이

Figure. Cost-of-goods-sold for various solar cell materials. Source: Lux Research

CIGS 장점: -결정질에 버금가는 효율-대기업의 적극적인 투자 (국내: 삼성, LG, 현대중공업)

CdTe: -Abound Solar(美) 2014, 1GW 증설 발표(0$0.6/W)

☞ 박막은 GW player 등장하는 2015년이후 본격적인 경쟁력을 갖출 것으로예상됨.

Beyond Grid-Parity미 증시에 상장된 중국 태양전지업체

Beyond Grid-Parity

PV Business의 핵심 경쟁력: Cost >> Efficiency

Source: Greentech Media Research, in SPI 2010, Oct 11 2010

Trina, Yingli$1.12/W

insolvency

가격경쟁력 및 businessmodel의 차별화 필요

Production and Cost Outlook: 2010-2015, the panel prices on the retail market will drop to less than USD 1 (EUR 0.727) a watt by 2012, driven by solid competition.

Prices are falling fast: Tough Competition Ahead

2. Si 태양전지 산업현황

Source: TSL earnings presentation

Q3/2010 중국 top tier gross margin rate-Trina: 37%-Yingli: 33.3%-Suntech: 16.4%

<Price and Margin structure of Top Tier Chines PV Companies>

28

Evolution of Std. c-Si PV Cells

3. Si 태양전지의 고효율 전개과정

Beyond Grid-Parity

Bell Lab1954

Martin Green (UNSW)

Texturing (Wet or dry Etcher)

3. Si 태양전지의 고효율 전개과정

Doping I: Shallow junction or Low doping

3. Si 태양전지의 고효율 전개과정

31

Doping: Shallow junction (Low doping) to Selective Emitter

장점 효율

High doping High lateral conductivity

Low contact resistance

Low Rs

(전도도 증가)

Low doping Low Auger recombination

Low impurity concentration

High Isc due to Blue response

High Voc due to low impurity

Illuminated area: low dopingUnder the finger: high doping

3. Si 태양전지의 고효율 기술요소

Selective Emitter

About 80% of the free carriers are photogenerated in the first 20m below the front surface.

shunt

Selective emitter

Low doping

Heavy doping

printing fired

Passivation I : Surface passivation (PECVD)

3. Si 태양전지의 고효율 전개과정

Silicon Atom

Oxison Atom

SiO2

Si

Interface Trap

(b)

Surface

Dangling Bond

(a)

Passivation I : Surface passivation

3. Si 태양전지의 고효율 전개과정

Passivation I : Surface passivation

3. Si 태양전지의 고효율 전개과정

35

Standard solar cell vs. PERL cell (25.0%)

3. Si 태양전지의 고효율 전개과정

37

기술

의중

요성

(효율

기여

도)

Ti/Pd 증착Ag 전해도금

Al/Ti/Pd 증착Al 증착, anneal

4. 상업화 기술적 이슈

Trends in c-Si PV Manufacturing Technologies

Selective Emitter

PERC/PERL

Beyond Grid-Parity

c-Si 태양전지는 궁극적으로 PERL cell로 진화

상업적으로는 PERL cell 기술을 단계적으로 적용( SE 후면 passivation 후면 locally diff(point 전극)

전극 (전면: SP도금, 후면 LFC 등등…)

tried-and testedoptimization

<New Approach>selective-emitter, plating, back-contact, back-junction, improved passivation

2013년 i-PERL 상업화 turnkey provider등장 가능성 매우 높음

Selective Emitter & Tech. Issues

3. Si 태양전지의 고효율 전개과정

Low doping & heavy doping의 장점을 최대화 Selective Emitter

Doping :1-step or 2-step, patterning

Metallization: screen printing, plating

Selective Emitter (SE) by Etching Paste

4. 상업화 기술적 이슈

Barrier coating(SiO2)

Local removal ofdiffusion barrier

Heavy doping Removal ofdiffusion barrier

Low doping

By SP etching paste

SiN as a barrier coating

PSGRLow doping

& PSGR

By SPetching paste

Heavy doping

2008년 상업화

(RT)

(350)

Etching paste resolutionFlat(40m), textured(80m)

Selective Emitter (SE) by laser doping or laser chemical processing

Synova/Fraunhofer ISE의laser chemical processing

UNSW의 laser doping

4. 상업화 기술적 이슈

Selective Emitter (SE): Manz-IPE Process

4. 상업화 기술적 이슈

-Only one additional processing stepcompared to the standard

-Phosphorous silicate glass (PSG) serves as dopant source for local second diffusion

. After the laser process:

. Standard PSG etch + SiNx

. Metallization: alignment essential

. Fully compatible with existing production lines

Selective Emitter (SE) : Schmid by Etch Back

4. 상업화 기술적 이슈

Selective Emitter (SE): Centrotherm FlexLine Plus

4. 상업화 기술적 이슈

Selective Emitter (SE): Innovalight & JA Solar

JA Solar 2010년상업화계획

4. 상업화 기술적 이슈

2009 24th EUPVSEC Hamburg, Germany

4. 상업화 기술적 이슈

-A phosphorus dopant paste is applied by screen printing in the same pattern as the contact grid-During the high-temperature step which occurs in a belt furnace, the silicon beneath thephosphorus source becomes heavily doped while the silicon between the phosphorusscreen-printed lines is only lightly doped

-This lightly-doped region created indirectly via gas phase transport of phosphorusbecomes the emitter of the cell

-After etching the diffusion glass. Metal lines are screen printed over the heavily dopedareas which requires an alignment

Doping Paste & Self-Doping Ag Paste

SP & inkjet printing dopant / Applied Materials Printer: 0.5% <

Selective Emitter Metallization Alignment

4. 상업화 기술적 이슈

Source: Proceeding of 24th EUPVSEC p1,502

Double Screen Printing

Stencil Screen Printing

Source: Proceeding of 24th EUPVSEC p989

UNSW LIP

Selective Emitter 상업화 기술

4. 상업화 기술적 이슈

Company 기술분류Process

Efficiency(%)

Cost RemarksDoping Electrode

Centrotherm laser C, 1-step SPmono: 18.2multi: 16.6

turnkey

Roth & Rau laser laser platingmono: 18.5multi: 17.0

Turnkey

(with UNSW)

Schmid

(inSECT)Etch Back C, 1-step SP 0.7

Gain:28€¢/wafer

Cost:8€¢/wafer* turnkey

Manz laser C, 1-stepSP

(HAP2400)0.5

Yingli, Bosch,Conergy

RenaLaser(LCP)

C, 1-step plating 1.0 With

Fraunhofer

InnovalightInkjet

(OTB/ARISE)C1 SP mono:19

Innovalight 사 ink 판매

~10¢/wafer (license fee)+ 투자비 (?)

With JA Solar

Applied Materials

Doping Paste

SP 0.5 Honeywell

Doping paste

MerckEtching paste

C, 1/2-step SP mono:18.5 Chinasunergy

* Investment, consumed materials and amortization costs.

Back Electrode

Full area Al thick film pasteDrawbacks:- Limited reflection of IR light- Fundamental limit in minimal rear side passivation- Bowing of thin wafer

Research focus:- Dielectric passivation of rear side- Metallization by local contacts

I-PERC (IMEC with Dow Corning)

UNSW (ink jet 방식 etching)

LFC (Laser Fired Contacts) by

Fraunhofer ISE

4. 상업화 기술적 이슈

Discovering the back side

4. 상업화 기술적 이슈

1% 이상 효율증대

P158

Passivation by ALD of Al2O3

태양전지의 passivation layer 종류에 따른emitter saturation current

1% 이상 효율증대

4. 상업화 기술적 이슈

Ion Implantation: 정교한 doping control ( one side & patterning), 공정단축

☞ roadmap to 22% with ion implantation

4. 상업화 기술적 이슈

- BP Solar’s newly developed Mono2™ silicon (mono like multi)-130m, 6” 18% ( IMEC’s advanced processes such as

dielectric passivation and a localized back surface field)

Mono like multi wafer:

18% < 셀 효율

4. 상업화 기술적 이슈

BP Solar: LGBC (laser grooved buried contact) (Saturn Cell)

5. 상업화 고효율 셀

< Saturn Module 특징 >

Licensed from UNSW in 1983

Laser grooving and electro plating processSelective Emitter

최고효율: cell (22%), module (~20%)

단결정에만 적용

공정복잡, 비용 높음

< UNSW’s Laser doping Process >

BCSC 공정 단순화

단,다결정 적용

Laser doping, LIP

Ex) Suntech’s PLUTO Cell

최초 laser로 edge isolation

최초로 laser에 의한 고효율셀 개발

SUNPOWER사의 후면전극 (Back-Junction Back-contact: IBC)

5. 상업화 고효율 셀

전극을 후면에 배치하여 shading loss가 없음 Isc

최고 24.2% 효율, 고품위 기판 및 semi-process로원가경쟁력 취약($0.8/W)

http://sharp-world.com/corporate/news/101201.html

Sanyo사의 HIT (Heterojunction with Intrinsic Thin layer) Cell

HIT cell의 특징은

n-type의 결정질 실리콘

전후면에 a-Si:H 박막을 이용한 저온접합형성 (전후면 passivation) High Voc (0.7V<)

300C 이하의 저온공정: cell 제조과정에서 cell이 받는 열 stress가 적어cell 파손 가능성이 낮기 때문에 wafer 박형화에 매우 유리한 공정 임.

TCO 사용으로 current resistance, 저온소성용 paste 사용으로 finger line 형성

5. 상업화 고효율 셀

Bifacial: up to 30% backside irradiance contribution

전후면 a-Si passivation: Voc(HIT)

후면 투명전극: 광흡수 증대(bifacial)

Record efficiencies for different heterojunction cell concepts

Source: Photon International, Oct. 2010

Standard Cell 의 진화 : 광 (direct, diffuse & reflected) 흡수 극대화

후면전극

Bifacial3) At up to 30% backside irradiance contribution

Ref) home power 134/ december 2009 & january 2010

Beyond Grid-Parity

6. 차세대 실리콘 태양전지Tandem

CIGS 효율 12-14%

Solyndra Cylindrical Modules Offer a Unique Greenhouse Energy Generation Solution; Light Passes Through Panels, Encourages Plant GrowthBusiness WireFebruary 22, 2011

Bifacial: 특수한 용도에 적합한 고효율 태양전지

Bifacial : BSF 층은 확산공정에서 형성SIN passivation 층: 양면에 도입장점: direct, radiant and scattered 광을 영면에서

흡수 효율증대

Gamma has a patent pending for the cost effective mass production process to make thin bifacial cells and another patent pending for a near 100% bifacial cell with >17% efficiencies on both sides.

Back Contact Solar Cell (BCSC)

Beyond Grid-Parity

6. 차세대 실리콘 태양전지

BCSC

IBC

MWT

MWA

EWT

IBC: interdigitated back-contact(back/rear junction)

MWT: metal wrap-throughMWA: metal wrap-aroundEWT: emitter wrap-through

BCSC 장점-전류증대 (lack of shading loss-up to 10%)-전면 passivation 최적화 유리-외관 미려-모듈효율 증대-모듈공정 단순화 (coplanar interconnection)

(inter connection from frontto back 자동화 어려움)

후면전극의 가장 큰 문제점

-공정 단축-(+)/(-) grid 및 junction을 전기적으로 절연시키는 sequence 개발:

절연 passivation

후면전극 : Metal Wrap Through (ECN)

Beyond Grid-Parity

6. 차세대 실리콘 태양전지

CIGS

-저가의 웨이퍼 사용 가능(p-type, 단결정, 다결정, UMG)-박형 웨이퍼 사용 가능(~120um)-전면 bus-bar를 후면으로 위치시켜 Shading loss를 줄임-국내에서는 S사, L사, H사 등이 기술 개발 단계-해외에서는 ECN이 대표적인 MWT 연구기관-Solland사에서 상업화 라인 구축 중, 2010년 하반기 상업화 생산-JA solar/ECN partnership MWT 생산

문제점: 표면에 grid line 존재, 효율한계

후면전극 : Emitter Wrap Through (NREL Advent Solar Applied Materials)

Beyond Grid-Parity

6. 차세대 실리콘 태양전지

후면전극인 EWT 태양전지:p-type 사용: carrier의 효과적인수집을 위해 다수의 홀을 통해 전도모든 전극이 후면에 위치

특징:-Emitter 면적 증가: hole 및 back-sidelow diff. length 물질 가능

(전면의 pn-junction은 carrier 수집에 유리)-전극공정이 한쪽에서만 진행-Back-side passivation: FF, Voc에 중요-SE: hole 및 전극하부에 고농도 도핑-후면에 base/emitter가 동시에 존재 shunt 가능성 고려 설계

Cost:-useful with low-quality solar-grade materials (dl ½ 가능)-SP 같은 low-cost 공정 적용 가능

저가의 웨이퍼 사용 가능(p-type, 단결정, 다결정, UMG)

박형의 웨이퍼 사용가능(~120 um, low-cost)

후면전극 (Shading loss 감소)

한화에서 EWT (Emitter Wrap-Through) 정부과제로 개발

Source: PV Technology Roadmap (Yole development), 2010. 8, SPI 2010, LUX Research, 2010.10

초저가

고효율

☞ 초저가 고효율에 가장 적합한 device 가능성 및 전문 기관의 예측

기판: N-type Cell, 고효율 원가절감 가능성 높음

Beyond Grid-Parity

-High Carrier lifetime (longer diff. length)

crystal defect & metal 불순물에 덜 민감☞ 동급 p-type에 비해 lifetime 5배

-광열화(B-O)를 피할 수 있다.-Less recombination-active defects(theoretical & experimental)

-Unused potential supply of n-type Si(반도체 대부분 p-type)

-고온공정 유리-저급 재료(ribbons, metallurigical)에 doping 유리-박형과 고효율에 n-type 유리

☞ P-type에 비해 최소 1% 효율증대 가능

Si (B-doped) Si (P-doped)

h h

P-type wafer N-type wafer

N-type wafer by P-doping P-type wafer by B-doping

Major issue:B-doping, Surface passivation: (SiN not work for N-type)

Sunpower (IBC), Sanyo(HIT) Std Cell 적용

PANDA Project: ECN과 공동으로 N-type 고효율 셀 개발 :ECN/Amtech자회사 (Tempress:diffusion furnace)After 13 month: pilot line,19%< 생산라인, 18.5%<,2012년 20% 기대

N-type cell (Supermono)

6. 차세대 실리콘 태양전지

PERC Cell pilot scale production: multi module record 갱신

Beyond Grid-Parity

6. 차세대 실리콘 태양전지

PERC structure:(rear passivation & point contact)Cell: 18.2%Module: 17.6%

PERC structure:(rear passivation & point contact)Cell: 18.45%Module: 17.84%

선도업체들의 고효율 cell 전략: PESC/PERC/PERL, HIT, N-type & 후면전극

Beyond Grid-Parity

6. 차세대 실리콘 태양전지

Cell device Cowork

Suntech Pluto cellMWTEWT Pluto Cell:17.2%, 18.9% UNSW

Sanyo HITQD

Sharp Back Contact Solar Cell 상업생산 개시

Q-Cells Back Contact Solar Cell

Yingli N-type Cell (PANDA Project) 18.5%< (cell) ECN

JA solar SECIUM (Si ink-SE)

MWT

18.9% (cell)

ECN

Trina Back Contact Solar Cell NUS

Kyocera MWT 17.3 (module)

Mitsubishi STD cell 최적화 19.3% (multi)

Bosch SEMWTEWT

PV Cell 효율전망

20%

25%

2010 2020

Standard cell

High efficiency cell(20% <)

(Non-standard cell & highest-quality wafers) Revolution 필요

Beyond Grid-Parity

15%

monomulti

7. Beyond SQ limit

박형 태양전지: 원가절감

Beyond Grid-Parity

IMEC에서 예측하는 결정질 실리콘 박형화 추세

Sanyo ultra-thin HIT solar cell with a thickness of 98μm, 22.8%.

SiGen : kerf-free wafering via an implant-and-cleave process that is still in the early stages of development but could yield wafers with thicknesses down to 20 microns.

7. Beyond SQ limit

PRIMA project (Plasmon Resonance for IMproving the Absorption of solar cells)

Beyond Grid-Parity

Project seeks structures to improve solar cell efficiency (03/30/2010 6:31 $ EDT)

-IMEC (Leuven, Belgium)주도 collaborative research project

-Iimprove the efficiency and cost of solar cells though the use of metallic nanostructures.

-Funding: European Union's 7th framework program for ICT (FP7) and includes: 3년간 2.3 million euro

-Partner: Imperial College (London, UK), Chalmers University of Technology (Sweden), Photovoltech NV (Tienen, Belgium), QuantaSol Ltd. (Kingston-upon-Thames, England) and Australian National University.

-Certain specifically nanostructured metallic surfaces have shown the ability to absorb and intensify light at specific wavelengths. This is because the incoming light results in a collective oscillation of the electrons at the metal's surface, known as plasmons. Plasmonics can be exploited to transmit optical signals through nanosized interconnects on chips, in nanoparticles that recognize and interact with biomolecules, or in solar cells.

With solar cells, metallic nanostructures can boost the absorption of light in the cell's photoactive material. With enhanced light absorption, it is possible to produce cells with less base material and thus thinner, lighter and lower-cost cells. Metal nanostructures can improve the absorption in a variety of solar cells including crystalline silicon, cells based on high-performance III-V semiconductors, or organic and dye-sensitized solar cells.

-적용: c-Si, 박막, DSSC 등

7. Beyond SQ limit

Down-convert: absorb blue or UV photon and emit two photons at longer wavelength (MPG).

Light Modulation by ARC

7. Beyond SQ limit

Down-shift: absorb blue or UV photon, emit radiation at w wavelength where the solar cell absorbs efficiently

Tandem Solar Cells

A solar cell with a “single junction” is

thermodynamically limited to ~33% AM1.5G

efficiency under one sun conditions.

-This efficiency limit is called the Shockley-

Queisser (SQ) limit

• Exceeding the SQ limit:

-Tandems optically filter spectrum, so each cell

received a narrower spectrum

-Tandem cell costs too much and basically

limited by the band gap of the materials.

• Quantum dot*

-Band gap of QD is tunable by the size.

-Various band gap from same materials.

*Quantum dots, also known as nanocrystals are a special class of semiconductor.

They range in size from 2-10 nanometers in diameter.

7. Beyond SQ limit

Tandem Solar Cells

Crystalline silicon’s bandgap of 1.1eV is a littlesmaller than the ideal 1.4eV. But amorphoussilicon has a bandgap of 1.6-1.7eV, so combiningthe two forms approaches an ideal type of solarcell. Though the HIT cell uses both amorphoussilicon and crystalline silicon, its emitter layer is stillessentially single junction. Its theoretical maximumefficiency, however, is a point or two higher than the27%-29% theoretical maximum of just crystallinesilicon, or about 30%. Though it will take some timeto achieve, this is where we are aiming.

VP Shinya Tsuda, general manager ofstrategic business promotion, R&Dand environmental management

7. Beyond SQ limit

Your beginning will seem humble, so prosperous will your future be. <Job 8:7>

Beyond Grid-Parity

흡수효율이 높은파장으로 광변조

탠덤 Si 태양전지

QD Application to c-Si Solar Cell

Pure QD Solar Cell

7. Beyond SQ limit

C-Si 태양전지 고효율 기술개발 전망

Beyond Grid-Parity

결 론

재료-저가 고품질의 다결정 (mono like multi)-박형화: 고효율, breakage감소, 자동화 (셀 & 모듈라인)-Si : P-type N-type (고효율 및 원가절감)

Cell device-단기(~2015): Std Cell PESC(SE)PERC (RP &PC) PERL (PERC+LD)-중기(~2020): 효율 20% 이상의 (Bifacial < 후면전극)이 50% 이상 점유-장기: Tandem (QD 접목), >25%

New technologies 도입-doping by Ion implantation-passivation by Al2O3

문제는 고효율과 저가화를 동시에 달성해야 한다는 점이다. China risk를 어떻게 극복하고 경쟁 우위를 확보할 것인가?

Crystalline Si PV Cell

The science is understood. The material is abundant. The products work.

The challenge is to bring the cost down.