Australian Centre for Advanced Photovoltaics Annual Report 2019 Stanford University Acknowledgements Written and compiled by Australian Centre for Advanced Photovoltaics Photos, figures and graphs Courtesy of Centre staff, students and others Copyright © ACAP May 2020 Please note that 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 within this report CRICOS Provider Code: 00098G TABLE OF CONTENTS 01 DIRECTOR'S REPORT 2 02 HIGHLIGHTS 4 03 ORGANISATIONAL STRUCTURE AND RESEARCH OVERVIEW 14 04 AFFILIATED STAFF AND STUDENTS 16 05 RESEARCH REPORTS Program Package 1 Silicon Solar Cells 22 Program Package 2 Thin-Film, Third Generation and Hybrid Devices 40 Program Package 3 Optics and Characterisation 74 Program Package 4 Manufacturing Issues 91 Program Package 5 Education, Training and Outreach 102 06 COLLABORATIVE ACTIVITIES Collaboration Grants 107 Fellowships 120 07 FINANCIAL SUMMARY 123 08 PUBLICATIONS 125 01 ACAP DIRECTOR'S REPORT Solar photovoltaics involves the generation of electricity directly from sunlight when this light shines upon solar cells packaged into a solar module. Silicon is the most common material used to make these photovoltaic cells, similarly to its predominant role in microelectronics, although several other photovoltaic materials are being actively investigated. The year 2019 was another important one for photovoltaics both in Australia and internationally. Rooftop solar installations in Australia (<100 kW) increased by over 2.1 gigawatts during the year, a 35% increase over 2018, the previous record year, with a similar increase in large commercial systems. Solar’s contribution to electricity generation in the Australian National Electricity Market increased to 7.6% averaged over 2019, likely to exceed 10% average in 2020. Even more importantly, this strong solar contribution has significantly improved the power network’s ability to meet peaks in electricity demand during summer heatwaves, where solar is proving much more reliable than conventional coal generators, whether new or aging. The other big news from an Australian perspective is that the Australian invented and developed PERC (passivated emitter and rear cell) in 2019 became the cell manufactured in the highest volume internationally. Also, on this international front, annual global photovoltaic installations increased to a new record of 124 gigawatts installed in 2019, according to market analysts. Photovoltaics also reinforced its position as one of the lowest cost options for electricity production yet developed, with wholesale module selling prices dropping 20% from 2018 averaged over the year. The lowest bid for the long-term supply of solar via a power purchase agreement decreased to US$16.54/MWh in July 2019. Bids in Australia dropped to more closely match this international benchmark with the Clean Energy Regulator reporting that bids of AUD$45/MWh were now not uncommon. By combining with the company’s pumped hydro storage assets, Snowy Hydro claimed it was now able to offer “firm” solar- and wind-generated power on demand at AUD$70/MWh, well below the price from “baseload” coal plant. Australia has played a major role in achieving these very low costs and is expected to play a key role in future cost reductions through the ongoing activities of the Australian Centre for Advanced Photovoltaics (ACAP), documented in this 2019 Annual Report. This is the seventh annual ACAP report, with ACAP activities supported by the Australian Government through the Australian Renewable Energy Agency (ARENA). ACAP aims to significantly accelerate photovoltaic development by leveraging development of “over the horizon” photovoltaic technology, providing a pipeline of improved technology for increased performance and ongoing cost reduction. A second aim is to provide high quality training opportunities for the next generation of photovoltaic researchers, with one targeted outcome being to consolidate Australia’s position as the photovoltaic research and educational hub of the Asia-Pacific manufacturing region. In achieving these aims, ACAP works with a wide range of both local and international partners. ACAP came into being on 1 February 2013 after the signing of a Head Agreement between the University of New South Wales (UNSW) and ARENA. During 2013, related Collaboration Agreements were signed between UNSW and the other ACAP nodes, Australian National University (ANU), University of Melbourne (UoM), Monash University, University of Queensland (UQ) and CSIRO (Materials Science and Engineering, Melbourne) and, additionally, with the ACAP industrial partners, Suntech Research and Development, Australia (SRDA) (partnership now transferred to Wuxi Suntech Power Co., Ltd.), Trina Solar Ltd, BlueScope Steel and BT Imaging, and subsequently with PV Lighthouse, Greatcell Pty Ltd and RayGen Resources Pty Ltd. Our major international partners include the NSF-DOE Engineering Research Center for Quantum Energy and Sustainable Solar Technologies (QESST), based at Arizona State University, and the US National Renewable Energy Laboratory (NREL), as well as the Molecular Foundry, Berkeley, Stanford University, Georgia Institute of Technology, the University of California, Santa Barbara and the the Korean Green Energy Institute. 2 ACAP ANNUAL REPORT 2019 This report covers the period from 1 January to 31 December 2019. Over the past seven years, ACAP has moved effectively to establish a high profile within the international research community. This is evidenced by the string of independently confirmed world records for energy conversion efficiency in efforts led by different nodes and for several different technologies since ACAP’s commencement. These include records for rear-junction silicon cells (ANU: 24.4%, 2013), overall sunlight to electricity conversion (UNSW, 40.4%, 2014; 40.6%, 2016), one-sun mini-module (UNSW: 34.5%, 2016), small-area “thin-film” CZTS (Cu2ZnSnS4) cells (UNSW: 9.5%, 2016; 11.0%, 2017), for >1 cm2 CZTS cells (UNSW: 10.0%, 2017), perovskite mini- modules (UNSW: 11.5%, 2016) and for >1 cm2 perovskite cells (UNSW: 18.0%, 2016; 19.6%, 2017; ANU: 21.6%, 2019). This tradition was continued into 2019 with key developments during the year summarised in the highlight pages immediately following this report. Particularly significant was the continued high level of recognition of ACAP’s impact through major local and international awards. In 2019, the Australian Academy of Technology and Engineering (ATSE) selected Professor Thorsten Trupke and Associate Professor Robert Bardos from the UNSW node for the prestigious Clunies Ross Award. The pair developed and commercialised photoluminescence imaging of silicon cells, ingots and wafers at UNSW, with development of this work supported over recent years by ACAP. This technology has been a gamechanger for the photovoltaics research community and the solar cell and module manufacturing industry, both locally and internationally. This and more detailed results described in the body of this 2019 Annual Report contributed to making 2019, once again, an extremely successful year for ACAP. I would like to thank ARENA for its ongoing financial support and also for the very effective involvement of ARENA personnel in supporting the ACAP program, both informally and via the ACAP National Steering Committee and the International Advisory Committee. I would additionally like to thank, in particular, all researchers affiliated with ACAP for their contributions to the broad range of progress reported in the following pages. Finally, I am pleased to be able to report that ACAP has taken another major step towards attaining its significant long-term objectives by achieving its key seventh-year milestones, on time and within budget. We look forward to similar progress in 2020 and in subsequent years. SCIENTIA PROFESSOR MARTIN GREEN Director, ACAP 3 02 2 019 HIGHLIGHTS OUTSTANDING CELL EFFICIENCY RESULTS Another outstanding result was obtained on solar-grade silicon, representing a low-cost and low-embodied energy alternative to A team at ANU, led by Professor Andrew Blakers, and comprising the standard silicon feedstock used to make silicon wafers and of Dr Matthew Stocks, Dr Osorio Mayon, Dr Katherine Booker and solar cells. These solar-grade silicon wafers often contain additional Christopher Jones, in collaboration with NREL, has fabricated a defects and impurities that can reduce device efficiency. A team at four-terminal tandem GaAs/silicon solar cell with a measured tandem ANU aims to demonstrate that, with specially developed processing efficiency of 29.8% at AM1.5G. This tandem solar cell with a silicon conditions, such solar-grade wafers can achieve cell efficiencies cell as the bottom cell and a GaAs top cell has demonstrated as high as standard silicon wafers and in 2019 reported the first efficiency above the theoretical limit of a single silicon cell. The solar-grade silicon solar cell with an efficiency of above 22%. The measured GaAs cell efficiency was 24.9% while the measured silicon wafers were n-type Czochralski-grown wafers made with silicon cell efficiency in tandem was 4.9%. The silicon cell is an upgraded metallurgical-grade (UMG) silicon feedstock, provided interdigitated back contact (IBC) device that was fabricated at ANU. by our partner Apollon Solar. The wafers were then fabricated into The GaAs cell was fabricated from epitaxial III-V layers grown at the