arc photov ovoltaics cs

261 Pages·2013·12.99 MB·English

Never Stand Still Faculty of Engineer ing ARC Photovoltaics Centre of Excellence
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201122
ARC
Photovoltaics Centre of Excellence

Annual Report 2012
(Final Draft)

UNSW
ARC Photovoltaics Centre of Excellence

The University of New South Wales
UNSW Sydney NSW 2052
Australia

Tel [phone]
Fax [phone]

http://www.pv.unsw.edu.au
CONTENTS
Page

1. DIRECTORS’ REPORT 1

2. HIGHLIGHTS 4

3. STAFF LIST 13

4. RESEARCH

4.1. INTRODUCTION TO RESEARCH 19
4.2. FACILITIES AND INFRASTRUCTURE 24
4.3. FIRST GENERATION: WAFER-BASED PROJECTS 37
4.4. SECOND GENERATION: SILICON, ORGANIC 92
AND OTHER “EARTH ABUNDANT” THIN-FILMS
4.5. THIRD GENERATION: ADVANCED CONCEPTS 169
4.6. SILICON PHOTONICS AND DEVICE CHARACTERISATION 225

5. ORGANISATIONAL STRUCTURE 241

6. PUBLICATIONS 243
1. DIRECTORS’ REPORT

Photovoltaics involves the direct conversion of light, normally sunlight, into electricity when falling
upon devices known as solar cells. Silicon is the most common material used to make these
photovoltaic cells, similarly to its key role in microelectronics.

The Australian Research Council (ARC) Photovoltaics Centre of Excellence commenced at the
University of New South Wales (UNSW) on 13th June, 2003 with funding initially until 31st
December 2007. Upon review in 2005 and 2006, this funding was extended until 31st December 2010.
Criteria for such extension included “progress of the Centre towards becoming independent of the
ARC Centres of Excellence Scheme for funding”. With the rapid growth of the photovoltaics industry
since the Centre’s commencement and the Centre’s strong and seminal links to this industry, the
Centre was clearly in a much stronger position for independent operation beyond 2010 than many
others in its funding cohort. Accordingly, while remaining under the ARC Centres of Excellence
umbrella beyond 2010 in recognition of the quality of its research, the Centre is now dependent upon
industry-related funding for research with near-term outcomes and upon more academically-
orientated ARC and international schemes for its long-term research. In recent years, project funding
provided by the Australian Solar Institute has been particularly important.

The Centre‘s mission remains to advance silicon photovoltaic research on three separate fronts, as
well as to apply these advances to the related field of silicon photonics. The educational activities of
the former Key Centre for Photovoltaic Engineering are also integrated into the Centre and into the
School of Photovoltaic and Renewable Energy Engineering (SPREE), which now hosts the Centre.

Over the period of funding, photovoltaics has become the world’s most rapidly growing energy
source, with markets increasing by over 40 times over this period. The electricity generating capacity
of new photovoltaic product installed in 2006 exceeded new nuclear power capacity for the first time,
with the gap widening significantly every year since. In Europe, photovoltaics has been the largest
source of new electricity generating capacity for each of the last two years, ahead of wind generators
and gas turbines. Reducing prices, at least partly traceable to past Centre initiatives, means the
technology has reached “retail grid parity” in many parts of the world, where the cost of electricity
generated using photovoltaics can compete at the point of use with normal retail electricity prices in
many parts of the world including most of Australia. This is expected to lead to a period of self-
sustaining growth with photovoltaics positioned to become one of the world’s major industries of the
present century.

Most present photovoltaic sales are of “first-generation” solar cells made from silicon wafers, similar
to the wafers used in microelectronics. The Centre maintains its world-leadership with these “first-
generation” devices, with international records for the highest-performing silicon cells in most major
categories (including the outright highest-performing cells and modules). First-generation Centre
research addresses the dual challenges of reducing cost and further improving efficiency. The rapid
growth of the industry is generating widespread interest in ongoing innovations of the Centre’s first
generation technology with several distinct technologies now in large-scale production with annual
sales of technology under licence now approaching several billion dollars.

Silicon is quite brittle so silicon wafers have to be reasonably thick, presently more than a tenth of a
millimetre, to be sufficiently rugged for processing into solar cells with reasonable yield. Without this
mechanical constraint, silicon would perform well even if very thin, even 100 times thinner than
present wafers. Centre researchers have pioneered an approach where very thin silicon layers are
deposited directly onto a sheet of glass with the glass providing the required mechanical strength. This
“second-generation” approach gives enormous potential cost savings. Not only are the costly
processes involved in making wafers no longer required, but also there is an enormous saving in
silicon material. Cells also can be made more quickly over the entire area of large glass sheets. The
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Centre is at the forefront of international research with such “second-generation”, silicon based
approaches, with commercial product from “spin-off”, CSG Solar, powering several megawatt fields
in Europe. The Centre is now investigating electron-beam evaporation of silicon onto the glass
substrate, a much quicker process than the plasma-enhanced, chemical deposition processes used to
date, and also diode laser processing of the deposited films.

Steps to broaden “second generation” activities from silicon to both silicon and carbon were boosted
by the appointment of a new academic staff member, Dr Ashraf Uddin, in 2009, with this organic
solar cell work supported by an ARC Discovery Grant. The activities were further broadened in 2010
by the award to Centre Postdoctoral Fellow Dr Xiaojing Hao of an Australian Solar Institute
Fellowship to develop “earth abundant” CZTS (copper-zinc-tin-sulphide) solar cell technology. By
combining these four relatively benign and abundant elements in appropriate proportions, a
tetrahedrally co-ordinated “synthetic silicon” compound can be produced with some advantages over
silicon, such as stronger light absorption and more potential for bandgap control by alloying with
similar compounds.

The “second generation” thin-films have a clear potential cost advantage over the silicon wafer-based
approach, due mainly to reduced material costs. In large enough production volumes, even these
reduced material costs will dominate thin-film costs. This has led to the Centre’s interest in advanced
“third-generation” thin-film solar cells targeting significant increases in energy-conversion efficiency.
Higher conversion efficiency means more power from a given investment in materials, reducing
overall power costs. The Centre’s experimental program in this area is concentrating on “all-silicon”
tandem solar cells, where high energy-bandgap cells are stacked on top of lower-bandgap devices.
The silicon bandgap is controlled by quantum-confinement of carriers in small silicon quantum-dots
dispersed in an amorphous matrix of silicon oxide, nitride or carbide. Cells based on “hot” carriers are
also of great interest since they offer the potential for very high efficiency from simple device
structures. Although their implementation poses daunting challenges, considerable progress on
addressing these continued to be made during 2012.

The final Centre research strand involves silicon photonics where the emphasis is upon using our
experience with solar cells, using light to produce electricity, to the reverse problem of engineering
silicon devices that use electricity to produce light. The Centre holds the international record for the
light emission performance from bulk silicon, in both electroluminescent and photoluminescent
devices. Emphasis is now upon exploiting our expertise in silicon light emission to develop new
techniques for silicon wafer and cell characterisation. A Centre “spin-off” company, BT Imaging,
remains the premium equipment supplier internationally using this approach.

In addition to these four research strands, the activities of the former Key Centre for Photovoltaic
Engineering have been integrated into the ARC Centre of Excellence. The ninth year of students from
the Bachelor of Engineering (Photovoltaics and Renewable Energy) program graduated during 2012.
This program has been enormously successful, attracting some of the best and brightest students
entering the University and providing the human resources to fuel the recent growth of the industry.
The seventh year of students have now graduated from the Centre’s second undergraduate program,
leading to a Bachelor of Engineering (Renewable Energy).

A significant relevant development during 2010 was the blossoming into full scale operation of the
Australian Solar Institute, of which the Centre was a founding member given its key role in the
Institute’s establishment. The Institute has announced the outcome of several rounds of funding with
some notable successes for the Centre. The Institute was absorbed into the Australian Renewable
Energy Agency (ARENA) at the end of 2012, with indications the increased resources of this agency
will help accelerate the local development and deployment of photovoltaics.

We thank all those who contributed to the Centre’s success during 2012. The present continues to be a
very exciting time for photovoltaics. More are recognising the possibility of a future where solar cells
provide a significant part of the world’s energy needs, without the environmental problems and
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escalating costs associated with the traditional approaches. The recent transition to “grid parity” is
expected to make the coming decade a time of rapid change for the industry, with an accelerated pace
of adoption of newer, lower cost technologies pioneered by the Centre.

……………………………………………… ………………………………………………
Professor Stuart R. Wenham, Professor Martin A. Green,
Director Executive Research Director

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2. HIGHLIGHTS

Joint Australian-US research Institute Led by UNSW

A new joint Australian–US research institute led by UNSW aims to foster rapid development of “over
the horizon” photovoltaic technology and establish Australia as the solar cell research and education
hub of the Asia-Pacific region. Federal Minister for Resources and Energy Martin Ferguson
announced the $35 million Australia-US Institute for Advanced Photovoltaics (AUSIAP) on 13
December 2012 as part of a raft of new programs and projects through the United States–Australia
Solar Energy Collaboration. The funding is part of an $83 million commitment, one of Australia’s
biggest solar research investments.

The new Institute is led by UNSW’s world record-holding photovoltaic researchers. It provides a
pathway for research collaboration between Australian and American centres and agencies and will
drive innovation and commercialisation.

“We welcome such a significant government investment in renewable energy research and we are
pleased that UNSW’s world-leading solar researchers have been recognised in this way,” said UNSW
Vice-Chancellor Professor Fred Hilmer.

Program leader Professor Green said: “The Institute (AUSIAP) will establish Australia as the
photovoltaic research and educational hub of the Asia-Pacific region. It combines our expertise with
America’s world-class facilities and creates a tangible pipeline to ‘over the horizon’ photovoltaic
technology”. “The Institute will also be fundamental to the training of the next generation of
photovoltaic research scientists and engineers,” he said.

The USAIAP will work with the recently announced National Science Foundation/US Department of
Energy Research Center for Quantum Energy and Sustainable Technologies (QESST). QESST is
based at Arizona State University, but involves other key US groups including Caltech, MIT and
Georgia Tech.

Other US collaborators include Stanford University, University of California – Santa Barbara, and
Sandia National Laboratories. Local partners include the Australian National University, University
of Melbourne, Monash University, University of Queensland, the CSIRO, and the NSW, Victorian
and Queensland governments. Also playing key roles are Australian and US-based companies – large
entities Suntech Australia, BT Imaging, Trina Solar Energy, BlueScope Steel and smaller start-ups.

The AUSIAP is supported by both the Australian Solar Institute and the US National Renewable
Energy Laboratory.

The Centre will also take the lead in another research project announced by the Federal Government
through the USASEC Open Funding Round, a $6.7 million project to produce Low cost, high
efficiency copper-zinc-tin-sulphide (CZTS) on silicon multi-junction solar cells in partnership
with Suntech R&D Australia, the National Renewable Energy Agency (NREL), and the Colorado
School of Mines.

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Professors Martin Green, Staurt Wenham and Suntech Win Collaborative Innovation Award

Athena Prib from NewSouth Innovations and Scientia Professor Stuart Wenham
accepting the Collaborative Innovation Award on behalf of the collaborative team.

Centre-developed technology has been recognised with a Collaborative Innovation Award at the
Cooperative Research Centres Association Conference in Adelaide on 16 May 2012.

Scientia Professors Stuart Wenham and Martin Green at the ARC Photovoltaics Centre of
Excellence at UNSW developed the Pluto technology in close collaboration with Suntech, the world’s
largest solar cell manufacturer, with funding from the Australian Solar Institute.

The Pluto technology is based on the UNSW-developed PERL cell, which in 2008 set a new world-
record for performance with 25 per cent efficiency.

The Pluto cell derivative is more economically viable to produce on a large scale, and recently
surpassed the 20 per cent efficiency barrier for converting the sun’s radiation into electricity, setting a
new benchmark for low-cost, mass produced silicon solar cells.

The cell features a unique texturing process that improves sunlight absorption, even in conditions of
low and indirect light, which enables higher efficiency.

“We recently broke through the 20 per cent target for solar cell efficiency, which many experts
thought was impossible and we’ve significantly lowered the costs compared to other technologies,”
says Green. “We believe Pluto technology has struck the ideal balance between conversion efficiency
and manufacturing costs to create a truly viable alternative for electricity production.”

“As we continue to refine the Pluto technology and push up the conversion efficiency, we have no
doubt that it will capture an increasing share of the global solar market,” says Professor Wenham,
who noted the importance of the partnership with Suntech, which allowed the cell to move beyond a
lab-scale device and become a commercial reality.

Dr Richard Corkish, who heads the School of Photovoltaic and Renewable Energy Engineering at
UNSW, says Australia is in a unique position to capitalise on its expertise in solar photovoltaics, and
could become a type of solar energy ‘Silicon Valley’ for research and development.

“Australia is at the ends of the Earth geographically – so you have to be really special to be at the
Centre of something from here, and we have that special status,” he says.
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ARC Linkage Grant Awarded For Buried Contact Cell Research

One of the world's most successful photovoltaic technologies is being "refined" for commercial
release by the University of New South Wales.

“The UNSW Buried Contact Solar Cell (BCSC) had over US$1 billion of product manufactured by
one of UNSW's licensees, BP Solar", said A/Prof CheeMun Chong. "Over the last twenty years we
have made some incredible improvements to this robust technology and now the Australian Research
Council has awarded us funding to take these improvements into production”.

The BCSC was implemented by BP Solar as their “SATURN” technology and reached efficiencies of
17% in commercial production in 2003. This is a significant result considering the production
efficiency of competing screen-printed solar cells was 1-2% (absolute) lower at that time.

The BCSC technology is listed amongst Australia’s Top 100 Inventions of the 20th Century as
determined by the Australian Academy of Technological Sciences and Engineering. Over the past
thirty years, screen printed cells silicon solar cells have dominated the PV market. Despite their large
market share, several fundamental limitations of screen printed solar cells have limited their
conversion efficiency. World-leading solar cell research at UNSW has shown that these limitations
can be overcome. The BCSC is one technology where improvements in solar cell structure have been
successfully transferred to the large scale production of large area, low cost commercial cells.

Structure of the UNSW Laser Grooved Solar Cell
(inset: A/Prof CheeMun Chong holding a laser grooved cell).

“UNSW has been awarded an Australian Research Council (ARC) Linkage Grant to support research
in improving the performance of the BCSC. Key additional areas of focus include the adoption of a
passivated rear surface as well as adapting the technology to suit new world-leading low cost silicon
wafers”.

“This project aims to increase the average commercial silicon solar cell efficiency from the current
17-19% to 23%. This improvement means that we will be able to generate 20% more electricity for
about the same cost and this is expected to be worth hundreds of billions of dollars per year if adopted
by the majority of industry. There is also the flow-on effect of significantly reducing the balance of
system costs as the higher efficiency solar products require less area, mounting structures, wiring and
transportation. The successful development of high efficiency, low cost solar cells will fast-track the
path for PV to reach grid parity in most countries world-wide”, said A/Prof Chong.
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