School of Photovoltaic and Renewable

Energy Engineering

Solar Cell Research at

University of New South

Wales

R. Corkish, Head of School

r.corkish@unsw.edu.au

www.pv.unsw.edu.au

UNSW at a Glance

Established 1949

Member Universitas 21, Group of Eight

Distinctive: only Australian university established with specific

scientific and technological focus

Large and highly regarded Engineering and Business faculties

Defined internationally recognised research strengths focusing on

contemporary and social issues in professional and scientific fields

• Applied research and strong industry connections

Cosmopolitan and International:

• Australian students from diverse backgrounds, many first in family

to university

• 1st Australian University enrolling International Students since

1951, now from > 120 countries; 20-25% International

• #52 QS Rankings (5 Stars);

• #132 ARWU Rankings (20130

• #85 Times Higher Education Rankings (2012-13)

• #81-90 Times Higher Education global reputation rankings (2013)

Faculty of Engineering

• ARWU ranking: 52-75 for Engineering (#1 in Australia)

• QS world ranking (2013): 33 in Engineering and Technology – 44 in EE; 37 in Mech; 15 in Civ; 31 in Chem; 29 in CompSci

• Budget approx. $134m

• 691 staff in 2013, including – 424 academic staff (247 teaching and research, and 177 research only)

– 267 professional and technical staff

• 9759 students in 2013, including – 4762 local & 2099 international undergraduate

– 902 local & 1116 international postgraduate coursework

– 426 local and 454 international research

• 9 Schools

Faculty Profile:

– http://www.eng.unsw.edu.au/system/files/publications/faculty_of_engineering_2013_profile.pdf

Context: The exemplary path until 2050/ 2100

Reference: "World in Transition: Turning Energy Systems Towards Sustainability (Summary for Policy Makers)," German Advisory Council on Global Change, Berlin 2003. www.wbgu.de

Context: Photovoltaics Growth

By region of manufacture (Source: Photon Int.;

GTM Research)

By region of use (Source:Solarbuzz)

0

5000

10000

15000

20000

25000

30000

35000

40000MWp

Year

USA

Japan

Europe

Rest ofWorld

Australian module and system prices

(courtesy of M. Watt, Australian Photovoltaics Association)

Learning

Curve

International Technology Roadmap for Photovoltaics (ITRPV) Results 2012, www.itrpv.net

• Down from 2011 due to GFC and

oversupply

• Asia dominating cell (95%) and

module production (86%)

• Mainland China produced 63% of

world cell and 64% of module

supply

• Production grew 5% in China but

declined 12% in RoW

PV production in 2012

Technology Share

School History

• PV research within UNSW

Electrical Eng. 1974 – 1998

• Separate Centre 1999 – 2005

• Pioneering UG photovoltaics

engineering program 2000

• PG coursework program 2001

• Second UG program 2003

• New School declared 2006

Undergraduate

Education

Engage with students

through: • Internships (60 days)

• Final year projects

• Employment

(S2, 2013 figures)

420 UG students overall

0

50

100

150

200

250

300

350

2000 2002 2004 2006 2008 2010 2012

No

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200

2003 2005 2007 2009 2011 2013

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ew

ab

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nerg

y U

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stu

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Year

Undergraduate Education

Two 4-year Engineering programs (420 students):

• Photovoltaics and Solar Energy (started 2000)

• Renewable Energy (started 2003)

(Session 2, 2013 figures)

0

50

100

150

200

250

300

350

400

450

500

2003 2005 2007 2009 2011 2013

To

tal

No

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Photovoltaics and Solar Energy

First such specialist degree globally

– Technology development

– Manufacturing

– Systems engineering

– Maintenance

– Reliability and lifecycle analysis

– Marketing

– Policy

Renewable Energy Eng.

• Begun 2003

• Development shared with Murdoch Univ., Perth

– Photovoltaics

– Energy Efficiency

– Solar thermal

– Wind

– Biomass

– Solar architecture

Postgraduate

Education • PG Coursework (46 students)

– Rapid growth 2007-10

– Strong AUD in 2011, 2012

– 1.5 year addition to 4-year BEng. or 4-year BSc

• Research degrees – PhD (93 students),

– Masters Research (10 students)

– Historically through Electrical Eng.

(S2, 2013 figures)

0

10

20

30

40

50

60

70

80

90

100

2001 2003 2005 2007 2009 2011 2013

No

. o

f P

G c

ou

rsew

ork

stu

den

ts

Year

0

20

40

60

80

100

120

2001 2003 2005 2007 2009 2011 2013N

o. o

f re

searc

h s

tud

en

ts

Year

Major Collaborations

• BEng (2+2) partnerships •Nankai University

•Sun Yat-Sen (Zhongshan) University

•Tianjin University

•Zhejiang University

•Nanchang University

•Beijing Jiao Tong University

•South China University of Technology

•Several Asian PV manufacturers • R&D collaborations and Intellectual property licenses

• Several former Centre members in key technical positions in major manufacturers

• ARC Linkage Projects with Suntech, Guodian, CSun and Tianwei

• QESST at Arizona State University

• US National Renewable Energy Laboratories

• Colorado School of Mines

Translated Texts

• “Applied Photovoltaics”

– Simplified Chinese (2008)

– Traditional Chinese (2009)

• “Solar Cells”

– Simplified Chinese (2010)

– Traditional Chinese (2010)

– Japanese (2010)

• “Silicon Solar Cells”

– Simplified Chinese (2011)

Tyree Energy Technologies Building

• Home to multiple interacting energy research activities – Australian Energy Research Institute

– School of Photovoltaic & Renewable Energy Engineering

– ARC Photovoltaics Centre of Excellence

– Cooperative Research Centre for Low Carbon Living

– Centre for Energy and Environmental Markets

– ARC Centre for Functional Nanomaterials

– Vanadium Battery Research Group of School of Chemical Science and Engineering

– School of Petroleum Engineering

• 6 Star GreenStar energy efficient building – 140kWpeak rooftop PV array of Suntech “Pluto”

selective emitter solar photovoltaic modules

– Gas-fired tri-generation

– Solar access control

– Labyrinth precooling of intake air

– Living laboratory

US-Australia Institute for Advanced PV Funded through the Australian Government’s United States- Australia Solar Energy

Collaboration, which is managed by the Australian Renewable Energy Agency • UNSW

•Australian National University

• University of Melbourne

• Monash University

• University of Queensland

• CSIRO

• NSF-DOE QESST (Arizona State Univ.)

• U.S. National Renewable Energy Laboratory (NREL)

• Sandia National Laboratories (U.S.)

• Molecular Foundry (U.S.)

• Stanford University

• Georgia Institute of Technology

• University of California - Santa Barbara

• Suntech R&D Australia

• BT Imaging

• Trina Solar Energy

• BlueScope Steel

• PP1: Silicon Cells

• PP2: Organic and Earth-Abundant Inorganic

Thin-Film Cells

• PP3: Optics & Characterisation

• PP4: Manufacturing Issues

• PP5: Education, Training and Outreach

AUSIAPV and ACAP

Generations of Photovoltaics

First Generation: Wafers/Ribbons

25% Efficient PERL Cell 17% Industrial Screen Printed Cell

Inkjet & Aerosol Jet Printing

Selective Emitter – 3 Technologies

• Semiconductor Fingers:

– Diffusion doped lines replace doped grooves

– Screen-printed metal fingers run perpendicular to diffused lines

• Laser Doped Selective Emitter

– Laser doping through/from dielectric layer

– Dielectric doubles as ARC and plating mask

– Laser doping gives heavily doped surface ideal for self aligned plating and selective emitter

• Transparent Fingers

– Semiconductor Fingers with laser doped lines

– Laser doped lines replace doped grooves

Dopant

Green laser selectively removes ARC dielectric and melts the silicon underneath

Molten Si freezing simultaneously incorporates heavy n-type Phosphorus doping

High temperature at localised regions only

Self aligned base metal plating into laser pattern – - low cost materials, - in line process flow, - fast LIP plating, - zero contact

Performance > 19% LDSE, > 20% D-LDSE

Laser Doped Selective Emitter

dielectric

p-type

N+ N++

Green Laser

Advanced Hydrogenation on UMG Material

Lifetime: <1 microsec several microsec >400 microsec

No Hydrogenation Standard Hydrogenation UNSW tricks

GaAsP – Si/Ge Tandem Cell • UNSW, AmberWave Inc., Veeco Inc., Yale University, University of Delaware,

Arizona State University, and the National Renewable Energy Laboratory.ASI –

supported partnership with Amberwave Inc.

• Si substrate

• Si/Ge alloy bottom cell to convert long wavelength light

• GAsP top cell to convert short wavelength light

• www.australiansolarinstitute.com.au/SiteFiles/australiansolarinstitutecomau/ASI

_Fact_Sheet_UFA001_Feb10.pdf

III-V – Si Tandem Cell on Virtual Ge Substrate • UNSW and the National Renewable Energy Laboratory.

• Low cost Si substrate

• Thin layer of crystalline Ge to be grown on a Si wafer by economic physical

vapour deposition – “virtual Ge wafer”

• GaInP/GaInAs top cells to convert short wavelength light

• www.australiansolarinstitute.com.au/SiteFiles/australiansolarinstitutecomau/ASI

_Fact_Sheet_UFA002_Dec20.pdf

Second Generation (Thin Films) - Si

Glass + SiN

AIC

interface

IAD 1800 nm

glue

‘Crater

’

‘Dimple’ Glass

‘Groove’

p+

p

n+

Metal

Si Insulator

Light

‘Crater’ ‘Dimple’

‘Moses’

Cell n Cell n+1

Image: CSG Solar

• Thin films on supporting substrate

– Amorphous/microcrystalline Si

– CIGS (In: CRITICAL (US DoE))

– CdTe (Te: NEAR-CRITICAL (US DoE))

– Crystalline Si on glass or conductive carrier

– Cu2ZnSnS4 (CZTS)

– Organic PV

– Perovskite

• Lower efficiency than wafers but lower

cost per m2

• Large manufacturing unit

• Fully integrated modules

• Aesthetics

Evaporated Cells

Main advances in evaporated cell technology:

• Improved Rsh due to sub-µm pinhole

shunt elimination.

• Aligned bifacial metallisation avoiding

non-linear (Schottky) shunting.

• Enhanced current due to diffuse

white paint back reflector and

absorber doping optimisation.

Plasmonic Evaporated Cells

Surface plasmon enhanced light-trapping (planar glass)

Si QD

metal nanoparticles

Second Generation (Thin Films) - Organic

• Potentially low cost, but:

– Low efficiency

– Poor stability

– High cost of current materials

• Ab-initio modelling of new

polymer materials

• Synthesis of new materials

• Cell fabrication, testing

• Improved light trapping

• Recombination reduction

• Hybrid organic/inorganic

Aluminium

Lithium fluoride

Donor/Acceptor

Indium Tin Oxide Glass

Donor (P3HT) Acceptor (PCBM)

CZTS thin films • Earth-abundant

• Low toxicity

• IBM demonstrated 9.7% in 2009

• Hydrazine-based solution

deposition

• Physical vapour deposition

• Reactive sputtering

Efficiency Loss Mechanisms

Two major losses – 50%

Limiting efficiencies 1 sun

Single p-n junction: 31%

Multiple threshold: 68.2%

qV

2. Lattice thermalisation

2

2

1. Sub bandgap losses Energy

3

Also: 3. Junction loss

4

4 4. Contact loss

5

5

5. Recombination

1

Limiting efficiencies Max. Concentration

Single p-n junction: 41%

Multiple threshold: 86.8%

Silicon based Tandem Cell

Thin film Si cell

Eg = 1.1eV

2nm QD, Eg =1.7eV

Si

QDs

defect or

tunnel

junction

SiO2

barriers

Engineer a wider band gap – Si QDs

Tandem Stack

Solar Cell 1

Solar Cell 2

Solar Cell 3

Decre

asin

g b

an

d g

ap

Tandem Stack

Solar Cell 1

Solar Cell 2

Solar Cell 3

Decre

asin

g b

an

d g

ap

SiC

SiO2

Si3N4 Substrate Substrate

Annealing

Si1-xCx

SiOx

SiNx

Silicon based Tandem Cell Deposition

•Si-rich Si (O,N,C) & Si precipitation

RF reactive sputtering

PECVD

•Direct Gas phase QD - PECVD

Future •Ge & Sn QDs – lower temp and/or low Eg

•Doping – p & n or modulation - two dielectrics

•Modelling of these and other structures

c-Si

SiC

0.9 eV

1.1 eV

0.5 eV

Si3N4

c-Si

1.9 eV

1.1 eV

2.3 eV

c-Si

SiO2

3.2 eV

1.1 eV

4.7 eV

Alternative matrices

Si72(OH)64, dQD = 14 Å

Hot Carrier Cell Extract hot carriers before they can thermalise:

1. need to slow carrier cooling

2. need energy selective, thermally insulating contacts

Spectrum Splitting for Concentrating PV

Selectivereflection

III-V array

Siliconarray

III-V array

Siliconcell

Selectivereflector

Photoluminescence Imaging

Images courtesy of BT Imaging

SPREE Research Topics (not PV devices)

• Cooperative Research Centre for Low Carbon Living

• Led by UNSW Faculty of Built Environment & SPREE

• Modular building energy efficiency (with Novadeko)

• Energy end-use efficiency

• PV and thermal and buildings

• www.lowcarbonlivingcrc.com.au

• PV modules and encapsulation

• Wind/solar resource forecasting

• Energy policy

• Combustion modelling

• Solar thermal technologies

Thanks for your attention!

“This Program has been supported by the Australian

Government through the Australian Renewable

Energy Agency (ARENA). The views expressed

herein are not necessarily the views of the Australian

Government.”