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
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
0
5
10
15
20
25
1940
1950
1960
1970
1980
1990
2000
2010
Eff
icie
ncy,
%
UNSW
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
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
• 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
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
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.”
