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Solar Cells – a perspective

Vikram Kumar Nanoscale Research FacilityIndian Institute of Technology

New [email protected]



0902022

National PhysicalLaboratory

NPL is the custodian of National Standards of Measurements in India



0902023

R&D Divisions of NPLPhysico-Mechanical

Standards

Electrical & Electronic

Standards

NPLRadio &

Atmospheric

Sciences

Cryogenics &

Superconductivity

Engineering

Materials

Electronic

Materials

MaterialsCharacterization

library, computing facilities,

internet, workshop,

glassblowing, electronicinstrumentation etc.

Employees – 854

Scientists – 197

Temp Scientists – 212

Budget: ~ 20 M$

Papers in 2008 – 259



090202 4

Major Areas @ NPL• MEASUREMENT SCIENCE

– STANDARDS, CALIBRATION, CHARACTERISATION

• ENERGY – PHOTOVOLTAICS, POROUS CONDUCTING PAPER FOR FUEL

CELLS, WHITE LED FOR LIGHTING

• SENSORS – MEMS, BIO, GAS, CONDUCTING POLYMERS

• ENGINEERING MATERIALS – LIGHT METALS, CARBON COMPOSITES, CONDUCTING POLYMERS,CERAMICS

• NANO TECHNOLOGY – CARBON NANOTUBES, BULK NANO METALLIC TUBES,

NANOCRYSTALLINE DIAMOND THIN FILM, MPECVD, NANO-SILICON CARBIDE, MESO POROUS OXIDE, NANO FERROFLUIDS,

NANOPHOSPHORS FOR LUMINESCENT DISPLAY• ENVIRONMENT

– GHG, OZONE, NOX , FACE, CRM, ANTARCTICA

• RADIO SCIENCE – IONOSPHERE, MOBILE COMM, OCEAN COMM



080523 6

MetrologyThe science of

measurement -METROLOGY - grewalong with the basicphysics.

Advances in science and

the development of hightechnology industrydemand improvedaccuracy inmeasurements.

In many areas such asdimensional metrology,electrical measurements,time and frequency,optics, the need foraccuracy during the last

fifty years has increasedb a factor of 3 to 10

In time and frequency

standards, the basis forspace navigation, the need

for accurate time hasincreased from 10-13 sec to

10-18 sec.The need for improveddimensional metrology isobvious with increasing

miniaturization. As we go tonanotechnology, we will

need even betteraccuracies.

In oil and gas industry thereis tremendous need for

accurate measurement offluid flow. Even a small



080523 7

World Trade Organization

• WTO is the international organizationdealing with the rules of global tradebetween nations

• Main purpose is to

– ensure smooth flow of trade – predictable and as free as possible

As part of WTO agreement all signatory nationsare committed to remove all barriers including

technical barriers to trade (TBT)

This requires the existence of an internationallyrecognized system of comparable and traceable

measurements



080523 8



080523 9

Mutual Recognition Arrangement

One of the well identified technical barrier to trade is in the fieldof standards and precision measurements The implementation of trade agreements under the WTOrequires the existence of an internationally recognized system of

comparable and traceable measurements To remove this barrier, it has been decided that testing and

calibration certificates issued by National Metrology Institutes(like NPL) should be accepted globally provided they meet

certain criteria In October, 1999 a „Mutual Recognition Arrangement‟ (MRA) was

signed by 37 member countries.

Today there are 67 signatories of the MRA

CIPM MRA brought together the NMIs, the RMOs and the BIPM

The CIPM MRA is seen as one of the key element inremoving the „Technical Barrier to Trade‟



sspl/nsd

Microwave Applications• Mobile Communication

systems – Cellular phones

– Wireless LAN

• Mobile satellite services

• Radars

•Missile guidance• Direct Broadcast Satellite (DBS)

• TV Tuners

• Collision Avoidance Radar



MONOLITHIC MICROWAVE INTEGRATEDCIRCUIT (MMIC)

GOLD Si3N4 DIELECTRIC

RESISTOR ION IMPLANTED

• Fabricate MESFET with

passive elements to obtainfunctional circuits

• inductors, capacitors,resistors, interconnects

• via holes and airbridges

• due to high frequencyoperation

– electromagneticinteraction

– parasitic capacitance

and inductance playsignificant role inperformance

• Circuit design and layout



12 GHz MMIC TECHNOLOGY

TECHNOLOGY FEATURES

EIGHT MASK PROCESS

ACTIVE DEVICE – MESFET with 0.7 m gate

Gm = 120 -140 mS/ mm. Ft > 18 GHz.

PASSIVE DEVICES –

SPIRAL INDUCTORS (0.3-13 nH)NITRIDE & POLY CAPACITORS ( 0.1 - 20 pF )

MESA RESISTORS (Rsheet = 300 0hms/ )

ION IMPLANTED MATERIAL

( N+ / N profile ) WITH RTA ANNEAL.

AuGe/Ni/Au OHMIC AND Ti/Pt/Au SCHOTTKY

CONTACTS. 2.5 um Pt/Au INTERCONNECT METALLISATION.

WET & DRY ETCH PROCESS.

Amplifier

Switch



Modelling & Design •Process modelling

•Device modelling

•Circuit modelling

•User’s requirements

•Design manual

Materials • CVD

• Schottky contacts

•Ion implantation

•Thermal annealing

Devices & measurements

•I -V data•Contact & series resistance

•Transconductance dispersion

•S-parameters

Processing &

characterization

•Sheet resistance•Electrical C-V

•Electrochemical C-V•SEM•SIMS

•Hall mobility

MMIC TECHNOLOGY DEVELOPMENT



A bit of History• 1983 Technology mission to

learn the trends• 1986 Position paper

• 1988 Special team to discusstechnology transfer

– Plessey asked

technology fee Rs. 10 Cr. – SSPL decide : we can do

it

• 1989 Project sanctioned

– Contract signed with SCLfor setting up andoperation

• 1996 GAETEC facility set up

• 1997 First MMIC fabricated

• 1998 Design Manualreleased 1992 – 2003 – my involvement



GALLIUM ARSENIDE ENABLINGTECHNOLOGY CENTER (GAETEC)

Pilot production center forGaAs MMICs

FACILITIES: • Class 10, 100, 1000 clean rooms• Lithography up to 0.5 m feature size• Ion implanter• Metallization & dielectric coater• Process characterization tools• Assembly & QC test setup• Design tools

TECHNOLOGY:• DEVELOPED at SSPL G7A - 0.7micron Ion Implanted Recessed

Gate MESFETs up to 12 GHz

G5A - 0.5 micron Ion Implanted Recessed Gate MESFETs up to 18 GHz

WAFER TRACK

MMIC AMPLIFIER



GAETEC Has a Modern Wafer Fabrication Facility with Class 10, Class 100 Cleanrooms Housing

State- Of- Art Equipment

GAETEC FOUNDRY



Lift Off Processor

Photolithography Bay

Ion Implanter



Thermal, E-Beam And sputtering System For

Deposition of Metal layers

Deposition Bay

Photoresist Processing System



ऊरजा



Per capita Energy Consumption



16 TW

sana 2100 tk 30 TW kI AavaSyakta haogaI



23

Renewable energy sources

Sun delivers 10,000times the energyneeded worldwide



090723 24

Depleting Supplies - Limited ResourcesPollution, Greenhouse Gases – GlobalWarming

Political & Economic Issues: Dependence

on Other Countries

Will become more expensive

Disposal: e.g., nuclear fuel is toxic and its disposalis ongoing environmental issue for centuries,

disastrous in case of accident. Less Efficient

Technical e.g., Transmission Loss

Year 2100:CO2 Level : 2.5-3.5x

Temp Rise: 1.4-5.4˚C

Fossil Fuels (meets 88% of the global energy demand)

38% Oil26% Coal24% Gas

Nuclear: 6.5%

Hydro: 2.2%

Climatically Challenged World

ा ा



ऊरजा ोत के आधज ऩ ऊरजा क खऩत



090723 26

Share of Energy



ऊरजा



090723 28

Renewable Energy • Clean Source of Energy

• Abundant Sources – Do not get depleted

• No Harmful Waste Products

• Many types can be generated at the location of use – notransmission loss

• No Greenhouse Gases

The photovoltaic energy conversion isthe most efficient process for utilizingthe solar energy requiring the least

number of conversion processes



090723 29

Some Facts….. Energy Demand: Y2000: 410 EJ (Exa=1018)

Y2050: 840-1050 EJ Y2100: 1460-1850 EJ

Possible Sources: Biomass: 270 EJ, entire agriculture mass

Wind: 65 EJ, installations at all potential locations

Nuclear: 250 EJ, 8000 new plants

Hydro: 50 EJ, dams at all rivers.

630 EJ

Over 1.5x1022 J (15,000EJ) of solar energy reach on theEarth everyday

Daily energy consumption of ~1.3EJ by human activity

Solar Energy:



ऊरज Millions of Barrels per Day (Oil Equivalent)

300

200

100

0

1860 1900 1940 1980 2020 2060 2100

Source: John F. Bookout (President of Shell USA) ,“Two Centuries of Fossil FuelEnergy” International Geological Congress, Washington DC; July 10,1985.

ईधन ऊरजा



090723 31

A global problem …



ईधन



ऊरजा



• ेऱ भॊडा वतमान खप द प 43 साऱ

• वतमान खप द प गैस के

भॊडा 64

साऱ • वतमान खप द प कोयऱा भॊडा 312 वष म

• पमाण ु ऊरात



वव सौ ऊरात का मानिच

सभी मानव रा

ko ilayao

आवयक ऊरात

pOda kr



पेम



37

Solar Energy Spectrum

• प थृवी क पह ुिने vaalaI पाव ~ 1000 W/m2



tIna rasto

सौ तजऩीय सौ पोटोवोलटक

सौ

जसजयनक



Energy Band Gap in Solids



Conduction in SemiconductorsElectrons and Holes



Semiconductors - n and p type

Impurities which can easily give upone electron

P in Si

Impurities which can easily acceptan electron

B in Si

त



43Silicon crystal lattice with dopant atoms

अतिाऱक SemiconductorsSolar cells use semiconductor materials: Silicon, GaAs, CdTe,CuInSe, amorphous Si

Semiconductors

n- type (doped with B, Al etc.) and

p- type (doped with P, As etc.)

Silicon has dopant atoms introduced to create a p-type and an n-typeregion and thereby producing a p-n junction.

The doping can be done by high temperature diffusion, where thewafers are placed in a furnace with the dopant introduced as a vapour



Semiconductor materials

• Intrinsic Semiconductors – Perfect, no added impurities, no defects

– Existence ?

– Only thermally generated carriers

• Extrinsic semiconductors – Impurities added to tailor the properties

• Doping

– Defects due to growth conditions

– Additional Carriers from these external dopants• May be excess electrons – n type

• May be excess holes - p type

Cystalline

Non crystalline

IV: Si, Ge

III-V: GaAs, InP,

GaNII-VI: CdTe, ZnO



45

PN-Junction Characteristics



Semiconductors

Photo-Voltaic = PV



47

15x10

-3

10

5

0

-5

C u r r e n t d e n s i t y ( A / c m

2 )

1.20.80.40.0

Bias (V)

Superposition principle

I (V) = ID (V) - IL

Current I

BiasV

Characteristic

under illumination

IL = ID (V) - I (V)

IL



48

in

SC OC

in

mp

e P

FF J V

P

P

Device characterizationCurrent

I BiasV

I sc

V oc

Characteristicunder illumination

FF P mp P in

ISC = 4.4 mA/cm2 FF = 0.52

VOC

= 840 mVe = 1.9 %

-4x10-3

-2

0

2

4

C u r r e n t d e n s i t y ( A / c m

2 )

1.00.80.60.40.20.0

Bias (V)

सौ सेऱ कायत साॊ



सौ सेऱ - कायत साॊ

101102

1. Light penetration depth

2. Generation of carriers inneutral regions

3. Diffusion of minority carriers

4. Collection of carriers fromdiffusion length

5. Majority carriers travel tocontacts

n

pe

h

h

Efficiency η = Elec power outSolar power in

Fill factor, series resistance

Operation of a solar cell



090723 50

Operation of a solar cell

b

Sb p –type Si base300 m

SiNx:H ARCn –type Si emitter

Al back contact

Ag front contacts

h+ h+ e- e-

e- e- h+

h+

e-

e-

e-

e-

Photons are absorbed in a semiconductor by generating

trillions of electron-hole pairs which need to live long enough by

avoiding recombination and get to the p-n junction, where theyare separated by an electric field and collected by contacts to

provide electricity to the load

e- e- e-

Progress in Crystalline Silicon Solar Cell



1941<1%

19546%

PESC198520%

PERL 199824.7%

197417.2%

PCC1988

22.3%

Progress in Crystalline Silicon Solar CellEfficiencies



52

Solar Photovoltaic Module



Stand Alone PV System

• Water pumping

Grid Tied PV System



Grid-Tied PV System

Components of Photovoltaic



090723 55

Components of PhotovoltaicPower

• Solar Cells – Material Options : Silicon, Cadmium Telluride, Copper

Indium diSelenide, (Gallium indium phosphide-Gallium Arsenide-Germanium)

• Photovoltaic Modules-- Glass, Tedlar, Encapsulant, Aluminium Frame,Junction Box, Connector Cables.

• Photovoltaic Systems

-- Battery, Power Conditioning Unit, Mountingstructure/Tracking device and Hardware



090723 56

Challenges & Efforts to meet them

1. Availability of solar cell materials to sustain the high

PV growth rate, (e.g. SoG-Si).

2. Improving efficiency industrial solar cells, (>16 20 % ?)

3. Reliability of performance (degradation issue).

4. Novel high efficiency concentrator PV system or lowcost 1 sun solar cells & modules for < 1 USD/watt

modules.

सऱकॉन सौ सेऱ म घाटा



• Sunlight contains a spectrum of photons of

varying energy E• If E< band-gap, the photon is useless

(Sub band loss)• If E>band-gap, then the excess energy

becomes heat (Hot carrier loss)

• Optical effects:• reflection loss

• incomplete absorption loss (in the

range of 300nm – 1100nm)• Collection efficiency loss

सऱकॉन सौ सेऱ म घाटा



–

• वत तृ फैऱस मॉडऱ एक सौ सेऱ केसैजतक अधकतम ऺमतज क गणनज है

• एकऱ p - n रशन के ऱए 31%



Shockley Queisser Limit

पोटोवोलटक



पोटोवोलटक Direct conversion of Sunlight into Electricity

Conventional Silicon Solar cells

Single and Polycrystalline Silicon

Commercial Efficiency ~ 16 %

Efficiency at Laboratory scale ~ 26%

Thin Film Solar Cells

a Si , CdTe, CIGS and thin film crystalline Si

Commercial Efficiency ~ 10 % Efficiency at Laboratory scale ~ 16 %

Limitations

High Cost

Large Area Limitation

Less Flexibility

Search for cost effective

alternatives

Nanocomposite/organic Solar

Organic Solar cells

वभन कनीक के सौ सेऱ



वभन कनीक क सौ सऱ क बारा हसेदा

ी ौ े



द सू पीढ सौ सेऱ

C ti l di f th t t f



Cross-sectional diagram of the structure of atypical CdS|CdTe solar cell.

Peter L M Phil. Trans. R. Soc. A 2011;369:1840-1856

©2011 by The Royal Society

C ti l di f th t t f



Cross-sectional diagram of the structure of atypical CIGS solar cell.





Harry Atwater, Albert Polman

nature materials, 9, 205, 2010

ी ी ौ े



तीस ऩीढ क सौ सेऱ



Organic solar cells

Small molecules(vacuum evaporation)

Conjugated Polymers(spin process)

Organic/inorganic hybrid(spin process)

Why Organic Photovoltaics



69

Why Organic Photovoltaics• Solar energy demand has grown at

a rate of ~ 30% p.a. over the last

15 years• The global market for PV

installations estimated at 18 b €

• Currently the market is heavily

dependent on government

subsidies

Production facilities are >10xcheaper than those for any

traditional PV technology Low unit costs enable use

even for shorter lifecycles

New form factors(semitransparent foil) allowcompletely new applications

flexibility, weight, large area, low cost, tailored properties

Costs

Lifetime

Efficiency



Organic solar cells

DONOR ACCEPTOR

O

MeOn

MEH-PPV PCBM

Distributed Heterojunction



090202 71

Distributed Heterojunction

G. Yu and A. J. Heeger: J. Appl. Phys. 78, 4510-5 (1995)

• Mix electron acceptor and hole acceptor materials together

• Distribute active interfaces throughout the bulk • All excitons are within a diffusion range of an interface

• Exciton dissociation at the PPV/C60 interface

• Electrons transferred to one component, holes to the other

• Charges travel to respective electrodes

bi-layer and bulk-heterojunction



090202 72

bi layer and bulk heterojunction(blend) organic solar cells

Small molecular PV Cells



73

Small molecular PV Cells

S.No. V oc (V) J sc (mA/cm2) FF (%) (%)

1. 0.50 6.51 51.5 2.09

-2 -1 0 1 2

-0.02

0.00

0.02

0.04

0.06

0.08

0.10

0.12

C u r r e

n t d e n s i t y ( A / c m

2 )

Voltage (V)

Illuminated

Dark

ZnPc

Device active area = 9.1 mm2

ITO/ZnPc:C60/BPhen/Al

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

300 400 500 600 700 800

A b s o r b a n c e ( a . u . )

Wavelength (nm)

ZnPc

C60



Schematic diagram toillustrate theelectrochemical andelectronic processestaking place in a dye-sensitized solar cellunder operating

conditions.

Peter L M Phil. Trans. R. Soc. A 2011;369:1840-1856©2011 by The Royal Society

dye-sensitized solar cell



ौ े ी ौ े



चौथे ऩीढ सौ सेऱ

Colloidal Particles



Colloidal Particles• Engineer reactions to precipitate quantum dots from

solutions or a host material (e.g. polymer)

• In some cases, need to “cap” the surface so the dot

remains chemically stable (i.e. bond other molecules onthe surface)

• Can form “core-shell” structures

• Typically group II-VI materials (e.g. CdS, CdSe)

• Size variations ( “size dispersion”)

CdSe core with ZnSshell QDs

Red: bigger dots!

Blue: smaller dots!

Demonstration of Solar Cell.....



090202 79


P3HT: PCBM

P3HT: CdSe: PCBM

Jsc = 6.32 x 10-3 A/cm2

Voc = 0.44 V

FF = 0.435

= 1.23 %

Jsc = 8.88 x 10-3 A/cm2

Voc = 0.48 V

FF = 0.36

= 1.91 %

ITO/ PEDOT:PSS/ P3HT:PCBM/ LiF/ Al

ITO/ PEDOT:PSS/ P3HT:CdSe:PCBM/ LiF/ Al

Reduction of barrier at active layer- acceptor interface

-0.25 0.00 0.25 0.50 0.75

-1.5x10-2

-1.0x10-2

-5.0x10-3

0.0

5.0x10-3

P3HT: PCBM

P3HT: CdSe: PCBM

J ( A / c m

2 )

V (Volts)




090202 80


MEH-PPV:PCBM

MEH-PPV:CdSe:PCBM

Jsc = 2.88 x 10-3 A/cm2

Voc = 0.37 V

FF = 0.46

= 0.62 %

Jsc = 7.37 x 10-3 A/cm2

Voc = 0.41 V

FF = 0.40

= 1.47 %

ITO/ PEDOT:PSS/ MEHPPV:PCBM/ LiF/ Al

ITO/ PEDOT:PSS/ MEHPPV:CdSe:PCBM/ LiF/ Al

-0.25 0.00 0.25 0.50

-1.00x10-2

-7.50x10

-3

-5.00x10-3

-2.50x10-3

0.00

2.50x10-3

5.00x10-3

7.50x10-3

1.00x10-2

B

MEH-PPV: PCBM

MEH-PPV: CdSe: PCBM

J

( A / c

m 2 )

V (Volts)A

• CdSe QDs have a range of electron affinities reported from 3.5-4.5 eV helpin matching energy levels

• PCBM provides additional conducting path allowing significant

enhancement of electron transport at even low doping levels

PolymerNanoparticles Voc

(V)Jsc(mA/cm2)

EQE PCE(%) References



090202 81

OC1C10-PPV CdSe tetrapods 0.75 9.1 0.52 2.8 B. Sun et al., J Appl Phys

97 (2005) 014914

P3HT CdSe nanorods 0.62 8.79 0.70 2.6 B. Sun et al., Phys Chem Chem Phys 8(2006) 3557

APFO-3 CdSe nanorods 0.95 7.23 0.44 2.4 P. Wang et al., Nano Lett 6 (2006) 1789

P3HT CdSe hbranch 0.60 7.10 2.2 I. Gur et al., Nano Lett

7 (2007) 409 –14

P3HT CdSe nanorods 0.70 6.07 0.56 1.7 W. U. Huynh et al., Science 295 (2002)2425 –7

MDMO-PPV ZnO 0.81 2.40 0.39 1.6 WJE Beek et al., Adv Mater 16 (2004)1009 –13

MEH-PPV CdSe tetrapods 0.69 2.86 0.46 1.13 Zhou Y, Nanotechnology

17 (2006) 4041 –7

MDMO-PPV ZnO 1.14 2.30 0.26 1.1 WJE Beek et al., Adv Funct Mater 15(2005) 1703 –7

MEH-PPV CdSex Te1−x (CdSe0.78Te0.22)

0.69 1.57 0.49 Yi Zhou et. al., Nanotechnology 17(2006) 4041 –4047

MEH-PPV CdTenanocrystals

0.77 0.19 0.42 T. Shiga et al., Solar Energy Materials& Solar Cells 90 (2006) 1849 –1858

MEH-PPV PbS 1.00 0.13 0.21 0.70 AAR Watt et. al., J Phys

D: Appl Phys 38 (2005) 2006 –12

P3HT PbSe 0.35 1.08 0.14D Cui et al., Appl Phys Lett

88 (2006) 183111

Hybrid Organic-Inorganic Solar Cells



y g g

Polymer: Inorganic Nanocomposites based Solar cells

Cost Effective Efficient Electron Transport Strong Optical Absorption Efficient exciton dissociation

Prepared by Inexpensive Wet Chemical Synthesis

Possibility of Tailoring the Properties by varying the size of the nanoparticles- quantum size effect

Nanoparticle –polymer cells generally have a photoactive

layer consisting of interconnected semiconductingnanoparticles in a solid semiconducting polymer phase i.e.interpenetrating phases of semiconducting polymers and

nanoparticles

-

Luminescent Graphene Quantum Dots (GQDs) for Organic Photovoltaics Devices



-4

-3

-2

-1

0

-0.1 0.1 0.3 0.5 0.7 0.9Voltage (V)

C u r r e

n t d e n s i t y ( m A c m

- 2 )

10% ANI-GS

5% ANI-GQD

3% ANI-GQD

1% ANI-GQD

P3HT

Al

5.1 eV

4.2 eVh+

e-

4.7 eV

ITO

h

3.2 eV

3.55 eV

5.38 eV

Figure band diagram of the OPV device

P3HT -ANI-GQDs 1%

VOC =0.61V, ISC = 3.51 mA/cm2, FF = 0.53, = 1.14

Figure JV characteristics of the photovoltaic devices

V. Gupta et al., Journal of American Chemical Society 133, 9960-9963 (2011).

Modified PTB7 PCBM

Solar cell based on current polymers



-0.02

-0.015

-0.01

-0.005

0

0.005

0.01

-0.5 -0.3 -0.1 0.1 0.3 0.5 0.7 0.9

Voltage (V)

C u r r e n t ( A )

Isc = 13 mA

Voc = 0.799 V

FF = 0.591= 6.14

Isc = 15 mA

Voc = 0.825 V

FF = 0.454

= 5.61

Modified PTB7-PCBM

Poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-

b']dithiophene 2 6 di l]



0

0.5

1

1.5

2

2.5

3

300 400 500 600 700 800 900

Wavelength/ nm

I n t e n s i t y / a . u .

1.69 eV 1.63 eV

PTB7

Modified PTB7

b']dithiophene-2,6-diyl]

[3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-

b]thiophenediyl]]

PTB7

PTB7/PC60BM eff. = 3.0

Mod. PTB7/PC60BM eff. = 5.6-6.2



Cost Effective Efficient Electron Transport

Strong Optical Absorption Efficient exciton dissociation

Prepared by Inexpensive Wet Chemical Synthesis Possibility of Tailoring the Properties by varying the

size of the nanoparticles- quantum size effect



ऊरात ऱौटाने का समय Energy payback time



Breakdown of EPT for three PV technologies based on data given by Wild-Schoten [27].



gy p y

From top to bottom for c-Si:Si feedstock, Ingot + wafer,cell, laminate, mounting and

cabling, inverter, recycling.

From bottom to top for CIGSand CdTe: laminate,

mounting and cabling,inverter, recycling.

Current Manufacturers of



090723 9191

Silicon Feed Stock 2008(Actual)

(MT)Hemlock, USA 15500

Wacker, Germany 11100

Tokuyama, Japan 5900

REC, USA 6100Mitsubishi, Japan/USA 3400

MEMC, Italy/USA 5600

DC Chemicals 3100

Dow Corning 3000

M Setek 2500GCL 1800

Others 12000

TOTAL 70000

Technology Shares



090723 92

Technology SharesWafer based solar cells used to represent more then 90 % of the market until 2005.Strong increase of thin shares (a-Si & CIS) in 2006-2007 because of silicon shortage.

2005-2008Situation of hardshortage withinvestment anddevelopment ofalternative PV

technologies

2010-2012

2nd

situation of shortage alternative PVtechnologies will again gain market shares

Current Manufacturing Costs



090723 93

Current Manufacturing Costs

9%

2%

7%

7%

8%

67%

Georgia Tech/GT Solar 25 MWp $1.98/WpSpire 25 MWp $1.78/Wp

Arthur D. Little 10 MWp $2.10/Wp

Haynes/Hill 10 MWp $1.92/Wp

Materials

Depreciation

Labor

Overhead

Interest

SG&A

Economic Roadmap for Low-



090723 94

pCost High-Efficiency Solar Cells

$0.79–$0.91

$1.06

$1.20

$1.51$1.56

$1.85

$1.98

$0.60

$0.80

$1.00

$1.20

$1.40

$1.60

$1.80

$2.00

$2.20

Current

cost

Slurry

recycle

325 →

200 µm

wafers

$25 →

$20/kg

silicon

13.5% →

17%

cells

Other

materials

cost

reductions

Scale-up

to

100–500

MWp

M a n u f a c t u r i n g C o s t ( p e r W p )

Ajeet Rohatgi, Georgia Tech

Projected module manufacturing cost



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Projected module manufacturing cost

Expected decrease in thethickness of silicon solarcells

Improvement in Vocwith d/L due to BSFeffect

Occurrence in the Earth‟s crust and current costs of some



of the elements relevant to thin-film photovoltaics.



Annual production of some of the elements



prelevant for photovoltaics.



िड समतज



Wolden et al.: Photovoltaic manufacturing: Present status, J. Vac. Sci. Technol.

A, Vol. 29, No. 3, May/Jun 2011



These countries represent 98% of the world population99.7% of world’s GDP and 99.2% of world’s CO2 emission

And 99.5% of residential electricity consumption

30%/yr Growth would lead to 250GW/yr in 2020

द ुनयज क क ु ऱ अधषठजऩत PV ऺमतज



ु ु



From bottom to top: China, USA, ROW, Japan, EU.

30 TW in 2100



30 TW in 2100

• sana 2100 maoM saarI ऊरात सौ फोटोवोलटक haogaI

• lagaBaga 1 TW vaaiYak ]%pad haogaa jaao ABaI ka 100 gaunaa

hO

• [sako ilayao lagaBaga 1012 va maI xao~ caaihyao (106 वगत कऱोमीट )

• भा का क ु ऱ भौगोऱक ऺे 3,287,240 वगत कऱोमीट है •

[sako ilayao bahut saamaga/I AaOr ऊरात AavaSyak haOgaI

• @yaa yah hao payaogaa

Excitonic PV Research



Excitonic PV Researchin India

• National Physical Laboratory, New Delhi (~ 2.0%)

• Jawaharlal Nehru Center for Advanced Scientific

Research, Bangalore (~2.0%)• Indian Institute of Technology, Kanpur (~1.8%)

• Tata Institute of Fundamental Research, Bombay

• Indian Institute of Technology, Delhi

• University of Delhi, South Campus, Delhi• Jawaharlal Nehru University, Delhi



िवा कने बा



िवा कन बा

• सौ ऊरात वऻान ह श ु ह ुआ ~ 1970 • रीवाम न वऻान 250 + साऱ

वकस कया गया है • नेनौसाइॊस ऊरात पाॊण औ नई ौयोचगकय के वकास म सऺम

• सौ ऊरात



Water pumping SPV system installed in Punjab for irrigation

30 kW SPV Power Plant installed at Taj Mahal, Agra



j , g



100 kW diesel grid interactive SPV power plant (Agatti island, Lakshdweep)



CEL, India, made SPV Plant for Lightening installed

at Eco-Habitats in Tyrona National Park, Columbia

Solar energy in use



Tracked PV Array containing 16 panels



The integration of PV cells into a building at the Thoreau

Center for Sustainable Development Image courtesy of NREL's



115



Indian Energy Scenario



090723 117

Solar Power

Approx. 300 Sunny days

Average Daily Solar Energy Incidence 4-7 kWH/m2

PV Contribution to total power generation: 2MW <<1%

per Capita Consumption: US ~21x India (2004-05)

Generation: 145 GW (10-14% Shortage).

2020 Requirement: 1200 GW

d a e gy Sce a o



श ुया



I thank numerous persons who havecontributed to this presentation

Important Elements for crystalline- Si



090723 120

Solar Cell Design



090723 121121

PV Production: Global & India 4000



090723 122

2008 PV ShipmentInternational : ~5.95 GWIndian : ~150 MW

Cumulative Installation~18 GW: 1/1000th Energy Portfolio

Projected PV Production2010 : 14 GW

2030: 140 GW

1975 1980 1985 1990 1995 2000 20050

500

1000

1500

2000

2500

3000

3500

4000

A n n u a l P V P r o d u c t i o n ( M W )

Year

Compound Annual Growth 44%

2002-07

2006 2007-8 2008-9 2010BP Solar 13 36 85-128

Webel 8 100*Maharshi 5 15CEL 3 12BHEL 2 10Maharshi * 8 15Others 1

MBPV 80 200 750Signet Solar 300Solar Semiconductor 60 220HHV 15

Future InvestmentsSignet Solar (3*300MW) -10yrsReliance and 10 more US$ 5-6b Investment,Special Incentive Package Scheme 18b

USD

E i C

Issue: PV Cost ?????



090723 123

Solar Cell ~60%

Material ~40%Mold: 5-10%

Processing ~20%

Modules

SystemsInstallation, inverters, batteries

$3-$5 per peak watt

Experience Curve

10-1

100

101

102

103

104

105

106

10-1

10

0

101

102

Cumulative Production (MWp)

M o d u l e C o s t ( 2 0 0 3 $ / W

p

)

Extension of historic data 2003beyond, ~30% growth

PV prices reduce by ~20% for every doubling of cumulative volume.

1975 1980 1985 1990 1995 2000 20050

20

40

60

80

100

C o s t p e r W a t t ( U S $ )

Year

Ref: 2007 USD

The Gap ….



090723 124

1975 1980 1985 1990 1995 2000 2005

8

10

12

14

16

18

20

22

24

26

E f f i c i e n c y ( % )

Year

Lab

SunPower Industry

Attainable Levels & Best Lab Efficiencies Lab & Industrial Efficiencies

How to bridge the gap between “ Lab & Industrial Solar Cell”

Year Cells Module1999 9.5 17

2000 14 17

YEARWISE PRODUCTION OF SOLAR CELLS &

MODULE



090723 125125

2001 20 20

2002 22 23

2003 25 362004 32 45

2005 37 65

2006 45 80

2007 110 135

2008 130 200

9.517 1417 2020 2223 25

36 32

4537

65

45

80

110

135 130

200

0

20

40

60

80

100

120

140

160

180

200

P

R

O

D

U

C

T

I

O

N

(

M

W

p )

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

YEAR

MODULE

Cells

Module

WORLD PV CELL/MODULE PRODUCTION(1991-2007 in MWp)



090723 126126

0500

100015002000

250030003500400045005000550060006500700075008000

Rest of World 5 4.6 4.4 5.6 6.35 9.75 9.4 18.7 20.5 23.42 32.62 47.8 83.8 141.5 322.5 714 1943 4188

Europe 13.4 16.4 16.55 21.7 20.1 18.8 30.4 33.5 40 60.66 86.38 112.8 193.4 311.8 476.6 678.3 1171 2020

Japan 19.9 18.8 16.7 16.5 16.4 21.2 35 49 80 128.6 171.2 251.1 363.9 601.5 833 926.9 932 1269

United States 17.1 18.1 22.44 25.64 34.75 38.85 51 53.7 60.8 74.97 100.3 100.6 103 138.7 154 201.6 233.1 431

Total 55.4 57.9 60.09 69.44 77.6 88.6 125.8 154.9 201.3 287.7 390.5 512.2 744.1 1194 1782 2521 4279 7910

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

From PV News, Photon International

Top Manufacturers of SiliconBased PV Technology



090723 127127

MOST MAJOR MANUFACTURERS ARE IN THEPROCESS OF CAPACITY EXPANSION

Manufacturer Prodn in 2008 2009 (Planned)(MWp) (MWp)

Q-Cells 581 800

First Solar 504 1000Sun tech Power 497 800

Sharp 473 600

JA Solar 300 500

Kyocera 290 400

Yingli 281 550Motech 272 415

Sun Power 237 450

Sanyo 215 300

Based PV Technology



090723 128

SANYO, Japan

Heterojunction with Intrinsic Thin-

layer (HIT)

BP SolarSaturn Cell

Sun Power Corporation,USACell with only back contact



090723 129

New Silicon Plants



090723 130



090723 131

93% solar cells use

silicon wafer technology

Thin film PV production capacity



090723 132

Amorphous Silicon Cell Employs ap i n Design



090723 133

p-i-n Design

M t l C t t

Proposed Solar Cell Structure µc Si:H by VHF PECVD at

μ-crystalline thin film silicon



090723 134

Metal Contact

n-layer (µc-Si:H)

i-layer (µcSi-H)

p-layer (µcSi-H)

Interfacial Layer

n-layer (a-Si:H)

i-layer (a-Si:H)

p-layer (a-Si:H)

a-SiC:H (Window layer)

TCO

Glass

Light

µc-Si:H by VHF-PECVD athigh growth rate

Hetrojunction with Intrinsic Thin Layer



090723 135

Hetrojunction with Intrinsic Thin Layer



Spectrolab’s Triple-Junction Solar Cells



090723 137

Nanostructured Solar Cells



090723 138

Nanostructured Solar Cells



090723 139



090723 140

J V Fill (%) Peak QE &

Current status of various solar cells



090723 141

Material system JSC

(mAcm-2) VOC

(V)

Fill

factor

(%)

Efficiency Peak QE &

Wavelength

Si (monocrystalline) 42.2 0.706 82.8 24.5 ± 0.5 >90% Amorphous Silicon 19.4 0.887 0.74 12.7 ~90%

CdTe (cell) 25.9 0.845 75.5 16.5 ± 0.5

GaInP/GaAs/Ge 14.4 2.622 85.0 32.0 ± 1.5

GaInP/GaInAs/Ge (tandem) 16.0 2.392 81.9 31.3 ± 1.5

DSSC > 10.0

Doped pentacene hetero-junction 7.7 0.90 0.66 4.5 -

Doped pentacene homojunction 5.3 0.97 0.47 2.4 36% at 650 nm Cu phthalocyanine /C60 bilayer

cell 13 0.53 0.52 3.6 18% at 620 nm

35% at 400 nm

MDMO-PPV /PCBM 5.25 0.82 0.61 2.5 50% at 470 nm

Dye sensitized solar cell with

OMeTDA hole conductor

5 0.90 0.56 2.56 38% at 520 nm

Best cell efficiencies



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PV Scenario in India



090723 144

• ~100 MW production – largest is Tata BPSolar with about 25 MW

• Expansion plans for all in the range of 20

to 40 MW• New players – Moser Baer PV to go up to

400 MW in 5 years. MBPV investing in a-

Si plant

R&D on Photovoltaics at NPLCrystalline Silicon: c- & mc-Si Cells (High & Industrial) >16%



090723 145

Crystalline Silicon: c- & mc-Si Cells (High & Industrial) >16%

Amorphous Silicon: a-Si:H and tandem cells, ~10%, 1cm2

Polymer Solar Cells: Conjugated Polymers, ~2%, 10mm2

Material Related R&D

mc-Silicon Ingot Growth Technology (US Patent)

PolySi – TCS Route on Si Filament Bulk SiGe (TEG)

“Diagnostic Tools & Equipment” for Solar Cells

Knowledge Based Service & Industrial Collaboration

Mechanical Load Tester

Reusable Split Mold

PSi ARC, 1978Graphite: ~1.65 gm/cm3

Crystalline Si cells:

Current PV R& D at NPL



090723 146

Crystalline Si cells:

1. Thin c-Si & mc-Si cells with BSF.

2. Studies on maximising light trapping, estimating and reducing

surface and bulk surface recombination losses, and, resistive

losses in c-Si and mc-Si cells.

Thin film Silicon cells:

System for high rate deposition of a-Si, c-Si films for solar cells.

Polymer and nano-structured cells:

Synthesis and characterisation of poly-octyle thiophenes and

functionalized CNT and nano-particles for application in solar

cells.

8 Registered PhD Students currentlyworking in PV related areas

Summary



090723 147

• The PV Scenario around the world is likelyto be dominated by bulk Si technology withcon tinuous improvements

• Thin Si film technologies will gain.• New structures based polymers and

nanostructures need a breakthrough

• NPL will increase the solar energy effortsin coming years



Remote lighting systems

Heat Receiver Coil

Solar Concentrator Optics



Heat Receiver Coil

Mirrors

Optical SystemShading Blocking

Mirrors

Shading & Blocking

Earlier Foreign Solar Dish Prototypes



44 kW - USA

SBP, Saudi ArabiaMDAC,USA

16 kW, SWIZ

60 kW, Swiz

Cummins, USA



A view of 10 kW (thermal) prototype of solar dish concentratordeveloped at CSMCRI, Bhavnagar during 2001-2003



Thank you

Thank you for your attention

perspective in photovoltaics

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