School of Photovoltaic and Renewable Energy Engineering

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 1 st 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

PV production in 2012 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

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

1940 1950 1960 1970 1980 1990 2000 2010 Efficiency, % First Generation: Wafers/Ribbons 25 20 UNSW 15 17% Industrial Screen Printed Cell 25% Efficient PERL Cell 10 5 0

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

Laser Doped Selective Emitter Green Laser 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

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

Advanced Hydrogenation on UMG Material Lifetime: <1 microsec several microsec >400 microsec No Hydrogenation Standard Hydrogenation UNSW tricks

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+, H 0 and H- H passivation of a defect often needs electrons for the bond formation H+ has no electrons, H 0 has 1, H- has 2 H+ cannot passivate some defects Transporting atomic hydrogen to regions needing passivation References: 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 H 0 is always a minority charge species 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., 39 th 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/cm 2 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 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 Cu 2 ZnSnS 4 (CZTS) Organic PV Lower efficiency than wafers but lower cost per m 2 Large manufacturing unit Fully integrated modules Aesthetics p+ p n+ Dimple Crater Metal Moses Insulator Si Glass Crater Groove Dimple Cell n Cell n+1 IAD interface AIC Light Glass + SiN glue Image: CSG Solar 1800 nm

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

Decreasing band gap Silicon based Tandem Cell Tandem Stack Solar Cell 1 Engineer a wider band gap Si QDs 2nm QD, E g =1.7eV Thin film Si cell E g = 1.1eV Solar Cell 2 Solar Cell 3 Si QDs SiO 2 barriers defect or tunnel junction Si 1-x C x SiO x SiN x Annealing Substrate SiC SiO 2 Si 3 N 4 Substrate

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 Selective reflector III-V array Silicon array Selective reflection III-V array Silicon cell

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! आपक ध य न क ल ए धन यव द 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.