School of Photovoltaic and Renewable Energy Engineering · School of Photovoltaic and Renewable...

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School of Photovoltaic and Renewable

Energy Engineering

RENEWABLE ENERGY

ENGINEERING EDUCATION

AND SILICON SOLAR CELL

RESEARCH AT UNSW

R. Corkish, Head of School

and COO, Australian Centre for Advanced PV

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);

• #101-150 ARWU Rankings

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

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

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)

Australian module and system prices

(courtesy of M. Watt, Australian Photovoltaics Association

• 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

(S1, 2013 figures)

447 UG students overall

Undergraduate Education

Two 4-year Engineering programs (474 students):

• Photovoltaics and Solar Energy (started 2000)

• Renewable Energy (started 2003)

(Session 1, 2013 figures)

Postgraduate

Education • PG Coursework (53 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 (108 students),

– Masters Research (9 students)

– Historically through Electrical Eng.

(S1, 2013 figures)

Major Collaborations

• BEng (2+2) partnerships •Nankai University

•Sun Yat-Sen 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 and Tianwei

• QESST at Arizona State University

• US National Renewable Energy Laboratories

• Colorado School of Mines

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 array of Suntech “Pluto”

selective emitter solar photovoltaic modules

– Gas-fired tri-generation

– Solar access control

– Labyrinth precooling of intake air

– Living laboratory

STAR - Solar Teaching And Research (imminent)

New site for industrial scale PV research tools (proposed National Facility)

• Sydney Olympic Park

• STAR basic - tools and services for a silicon wafer solar cell manufacturing line, plus existing tools for approved research projects,

• STAR Independent – acquisition of tools from partners to provide full ownership and control over the STAR toolset,

• STAR Complete – includes module lay-up, lamination and framing as well as full characterisation, measurement and environmental testing capabilities, site and building

AUSIAPV and ACAP

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 • 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

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

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

Green Laser

Hybrid Front Surface Design

• Hybrid screen-printing + plating

• Can use paste without glass

• Ag isolated from Si gives high Voc

• Ag paste has higher conductivity

• Ag paste does not react with plating

solutions or HF

• Avoids present Pluto problems:

- Solderability of interconnects

- Cu on rear electrodes

- Adhesion strength

• PVD2A silver paste

• Good conductivity

Lifetime: <1 microsec several microsec >400 microsec

No Hydrogenation Standard Hydrogenation UNSW tricks

Advanced Hydrogenation on UMG Material

Advanced Hydrogenation

• Key Issues for Hydrogen Passivation: – Hydrogenation sources on both surfaces (remote PECVD)

– Reactivity of atomic hydrogen determined by its charge state • Three charge states of hydrogen H+, H0 and H-

• H passivation of a defect often needs electrons for the bond formation

• H+ has no electrons, H0 has 1, H- has 2

• H+ cannot passivate some defects

– Transporting atomic hydrogen to regions needing passivation • Mobility determined by the H charge state

• H mobility varies by 4 orders of magnitude

• H charge state can be controlled by the minority carrier concentration

• H+ is dominant in p-type silicon

• H- is dominant in n-type silicon

• H0 is always a minority charge species

• References: – B. Hallam et al., “Hydrogen passivation of B-O defects in Czochralski silicon”, SiliconPV: March 25-27, 2013,

Hamelin, Germany (Energy Procedia 2013)

– S. Wenham and M. Green, “Advanced Silicon Wafer-based Solar Cell Technologies”, Shanghai New Energy

Conference: 15 May 2013, Shanghai, China

– B. Hallam et al., 39th IEEE PVSC: 16-21 June 2013, Tampa, FL, USA

Cell Results with Advanced Hydrogenation

– Hydrogenation process incorporated into cells with

localised rear laser doped contacts and PLUTO front • Standard commercial grade B-doped CZ

– Voc 681 mV

– Jsc 40.0 mA/cm2

– Low FF due to deactivation of B

– Efficiency > 20%

– Pseudo efficiency >23%

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

interface

IAD 1800 nm

‘Crater

‘Dimple’ Glass

‘Groove’

Si Insulator

‘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

• 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)

metal nanoparticles

Silicon based Tandem Cell

Thin film Si cell

Eg = 1.1eV

2nm QD, Eg =1.7eV

defect or

tunnel

junction

barriers

Engineer a wider band gap – Si QDs

Tandem Stack

Solar Cell 1

Solar Cell 2

Solar Cell 3

Tandem Stack

Solar Cell 1

Solar Cell 2

Solar Cell 3

Si3N4 Substrate Substrate

Annealing

Si1-xCx

Hot Carrier Cell Extract hot carriers before they can thermalise:

1. need to slow carrier cooling

2. need energy selective, thermally insulating contacts

Photoluminescence Imaging

Images courtesy of BT Imaging

Spectrum Splitting for Concentrating PV

Selectivereflection

III-V array

Siliconarray

III-V array

Siliconcell

Selectivereflector

SPREE Research Topics (not PV devices)

• ARC 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! आपका ध्यान के लिए धन्यवाद

“This Program has been supported by the Australian

Government through the Australian Renewable

Energy Agency (ARENA). The Australian

Government through ARENA is supporting Australian

research and development in solar photovoltaic and

solar thermal technologies as part of its commitment

to improving the competiveness of renewable energy

technologies and increasing their supply in Australia.

The views expressed herein are not necessarily the

views of the Australian Government, and the

Australian Government does not accept responsibility

for any information or advice contained herein.”

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