Research Seminars are open to the public and are run on alternate Thursdays.
Next Seminar Location:
UNSW Building H6 – Tyree Energy Technologies Building - LG03
Time: 12pm - 1pm
Professor Martin Green's
2012 SEMI Roadmap for Photovoltaics: Bigger, Thinner, Faster, Cheaper
27 June 2013
Laser crystallised Si thin-film solar cells
Laser crystallisation of thin silicon films on glass by CW diode laser has recently enabled much higher solar cell voltages than achieved previously for polysilicon-based cells grown on foreign substrates. This has inspired great interest in achieving low-cost modules with c-Si efficiencies. The UNSW Thin-Film Si PV group, in collaboration with Suntech R&D Australia, is leading the world in this area of research and is currently investigating several aspects of the technology. These include the intermediate layers, crystallisation conditions, emitter diffusion, Hydrogenation, light trapping and metallisation schemes as well as new characterisation methods for thin-film Si on glass. This talk will provide an overview of this work alongside a review of poly-Si thin-film research being carried out by groups around the world.
Jonathon Dore has been involved in PV since 2001, completing the BE (PV) at UNSW in 2005 before beginning work for CSG Solar. He was involved in the development of Crystalline Silicon on Glass thin-film solar modules in Sydney as well as for several years in Germany. Jonathon is now in the 3rd year of his PhD on laser crystallised thin-film solar cells, working with Martin Green and Sergey Varlamov in the Thin-Film Si PV group as well as working for Suntech R&D Australia on various projects.
Pollinate Energy: Bringing clean energy solutions to India's urban poor
Pollinate Energy is a not-for-profit social business which provides solar lighting and mobile phone charging to urban slum dwellers living without electricity in India. Founded by 5 young Australians in late 2012, Pollinate Energy has started 5 new microfranchises, sold around 500 lights and is working in over 130 communities. These microfranchises were started through a fellowship program where 9 students came to Bangalore in January to support the start up of these businesses. These students included 5 studying with the School of PV - thanks to Jacqui, Amit, Sanika, Jono and Kathy!
Pollinate Energy will run 4 more of these fellowships over the next year, starting 15 new businesses and launching 2 new products in the Bangalore region. If you'd like to support Pollinate Energy come to our event on June 1st! We will have Michael Caton (from the Castle) as guest speaker, tickets are on sale now at www.pollinateenergy.org.
Monique Alfris has almost a decade's worth of experience in environmental sustainability. Monique applied her degrees in Photovoltaic Engineering and Economics to improving the sustainability of the built environment in Australia where she gained experience in technical design, policy advisory services, and education. Following this she worked for the Green Building Councils of Mauritius and Ghana. As a Sustainable Energy specialist for Good Return, another Australian not-for-profit, Monique worked on small-scale renewable energy loan products with microfinance institutions across Asia, before finally landing in India to cofound Pollinate Energy. Pollinate Energy provides solar lights and mobile phone chargers to urban slum dwellers through a microfranchise and microfinance model.
Support our current crowdfunding campaign to provide solar energy to India's urban slums: www.chipin.org.au/project/pollinateenergy
Time-resolved spectroscopy and carrier dynamics in Au nanoclusters and carbon nanodots
It has been shown that ultrafast and time-resolved spectroscopy techniques, such as ultrafast sum-frequency, transient absorption, and TCSPC, are powerful tools to investigate carrier/energy dynamics. It is therefore very useful for investigation of temporal processes occurring in various systems in physics, chemistry, materials science, and engineering. Au nanoclusters and carbon nanodots have emerged as novel luminescent material. They have been shown distinctive optical properties and great potential to be applied in bioimaging, biosensor and photonics, as an alterative to organic dyes and semiconductor quantum dots, owing to excellent biocompatibility and high chemical/photo-stability. Fundamental understanding is critical important to facilitate the applications. In this talk, the general ultrafast and time-resolved techniques are briefly summarized. The optical properties, in particular the carrier dynamics occurring in time scale of femtosecond up to microsecond, of novel Au nanoclusters and carbon nanodots are investigated by various time-resolved techniques, which shows very prospective for applications in bioimaging and photonics.
Dr Xiaoming Wen, received PhD from the Centre for Atom Optics and Ultrafast Spectroscopy (CAOUS) at Swinburne University of Technology in 2007, for ultrafast spectroscopy and carrier dynamics in semiconductor nanostructures. Then he performed postdoctoral research at University of Melbourne for charge dynamics in organic semiconductors, and Academia Sinica in Taiwan for ultrafast, time-resolved and single molecule spectroscopy in colloidal nanoparticles. He joined in SPREE at UNSW for the research of hot carrier solar cells in 2012. He has designed and set up various ultrafast, time-resolved spectroscopy experiments. He has established expertise in ultrafast and time-resolved spectroscopy and extensive applications in carrier/energy dynamics in nanomaterials, including semiconductor, metal and organics. He has published 70 refereed papers in leading journals, such as APL, JPCC, PCCP, Adv. Opt. Mater., Nanotechnology and New J Phys.; and published one academic book on ultrafast spectroscopy.
Low temperature anodically grown silicon dioxide films for solar cell applications.
Centre for Sustainable Energy Systems, ANU
This presentation will discuss anodically grown silicon dioxide films for the surface passivation of silicon solar cells. These anodic SiO2 films are formed by two processes, (i) by applying a positive 30 V bias across two silicon wafers immersed in nitric acid (HNO3) and (ii) by applying an alternating ±30 V bias across two silicon wafers immersed in HNO3. After annealing these films at 400 ºC in oxygen and forming gas, a low surface recombination velocity of S < 20 cm/s is achieved. It will be shown that the SiO2 thickness increases as the HNO3 concentration is decreased, indicating water is the primary source of oxygen for the anodic oxidation process. It will be demonstrated that the HNO3 purity has a substantial impact on the repeatability of S. When the HNO3 impurity level is in the parts per million range, S of 10–1000 cm/s results. However when the impurity level is reduced to parts per billion, S ranges between 15–30 cm/s. It will be shown that these anodic SiO2 films degrade when exposed to the ambient air, however from our investigation, it is found that water moisture is the main source of degradation observed in these anodic SiO2 films. It is demonstrated, that a simple, low temperature anodic oxidation procedure provides a level of passivation that is suitable for high efficiency devices.
Nicholas Grant received his B.Sc degree with first class honours in physics from the University of Adelaide, S.A, Australia in 2007 and his PhD degree in engineering (photovoltaics) from the Australian National University, Canberra in 2012. Currently he is an ASI postdoctoral fellow at the Australian National University conducting research in the Centre for Sustainable Energy Systems. His area of research is developing low cost dielectric films for PV devices and enhancing the efficiency of sliver solar cells.
Professor Martin A. Green: Evolution of High Efficiency Silicon Solar Cell Design
Lecture 2: High Efficiency Design of Silicon Solar Cells
Scientia Professor Martin A. Green, AM, FAA, FTSE, FIEEE, FRS
UNSW SPREE; Australian Centre for Advanced Photovoltaics
Professor Martin A. Green, author of six books, twenty-one book chapters and over three hundred research papers explains the history of the silicon solar cell.
Lecture 2: High Efficiency Design of Silicon Solar Cells
1. Enter the modern era
2. Principle I - "Dark/Light Superposition"
3. Improving "emitters"
4. Principle II - "Dark/Light" Reciprocity
5. Evolution of Si Cells design I
6. "Light Trapping"
7. Evolution of Si cells design II
8. Principle II - "PV/LED" Reciprocity
9. The future
Professor Martin A. Green: Evolution of High Efficiency Silicon Solar Cell Design
Lecture 1: Evolution of Silicon Solar Cells
Scientia Professor Martin A. Green, AM, FAA, FTSE, FIEEE, FRS
UNSW SPREE; Australian Centre for Advanced Photovoltaics
Professor Martin A. Green, author of six books, twenty-one book chapters and over three hundred research papers explains the history of the silicon solar cell.
Lecture 1: Evolution of Silicon Solar Cells
1. Recent developments
2. Early PV history
3. The first pn-junction
4. Conventional space cells
5. Key pointer pn junctions
6. Enter the modern era
QBotix: A Silicon Valley Story of Improving Solar Through Robotics
QBotix (http://www.qbotix.com/) is a U.S. Department of Energy SunShot Incubator Grant Recipient that has developed a novel new tracking system that utilises a pair of rail mounted robots to replace the motors and actuators found in traditional single and dual axis tracking systems. Rather than have a complete tracking system attached to the base of each array, the robot traverses between arrays adjusting each set of panels according to the local sun table. By reducing capital costs and boosting output via dual axis tracking, the QBotix Tracking System improves project economics and lowers the cost of electricity produced by photovoltaics.
The talk will provide background on the company, a discussion around the technology, the value proposition to solar, and future prospects.
Sunlight-driven water splitting in photoelectrochemical (PEC) cells
Sunlight-driven water splitting in photoelectrochemical (PEC) cells is an attractive method for direct solar-to-fuel energy conversion. Hematite (Fe2O3), also known as rust, is a promising light absorber for PEC cells despite its non-optimal optoelectronic properties. An interesting strategy to improve its energy conversion efficiency is functionalization with metallic nanoparticles supporting localized surface plasmon resonances. In this talk, the beneficial effect of metallic nanodisks on the performance of photoanodes based on ultra-thin hematite films are presented and discussed. Experiments and calculations are combined to investigate – and partly elucidate - the mechanisms behind the observed improvement [1,2]. Moreover, measurements of the faradaic efficiency of water splitting on the surface of hematite are presented .
Beniamino Iandolo obtained a Bachelor degree in Engineering Physics from Politecnico di Milano (Italy) in 2007 and a Master degree in the same subject, from Politecnico di Milano, in 2009. Beniamino performed the wok for MSc thesis at Chalmers University of Technology, Göteborg (Sweden), during a one year exchange project between 2008 and 2009.
In 2010 I returned to Chalmers to join the Applied Physics department as PhD student. He is currently involved in a research project in the area of sustainable hydrogen production from water and sunlight. His research focus is on understanding and improving the photoelectrochemical (PEC) properties of hematite (a-Fe2O3), a promising light absorber for PEC cells.
 B. Iandolo and M. Zäch, Aust. J. Chem., 2012, 65, 633–637.
 B. Iandolo, T. J. Antosiewicz, A. Hellman and I. Zorić, PCCP, 2013, DOI: 10.1039/c3cp44483j.
 B. Iandolo et al., In preparation.
Role of Surfaces and Their Analysis in Photovoltaics
Professor Robert Opila
University of Delaware
Surface chemistry is intrinsically related to the performance of solar cells. In solar cells the generation and collection of charge carriers determines their efficiency. Effective transport of charge carriers across interfaces and minimization of their recombination at surfaces and interfaces is of utmost importance. Thus, the chemistry at the surfaces and interfaces of these devices must be determined, and related to their performance. In this talk we will discuss the role of two important interfaces. First, the role of surface passivation is very important in limiting the rate of carrier recombination. We have been studying organic passivants on H-terminated Si surfaces, and establishing extremely low surface recombination rates. Here we are combining spectroscopic measurements of the surface of a-Si device with electrical measurements to ascertain what factors determine the quality of a solar cell passivation. In addition, the quality of the heterojunction interface in a ZnSe/CdTe solar cell affects the output voltage of this device. X-ray photoelectron spectroscopy gives some insight into the composition of the interface, while ultraviolet photoemission yields the relative energy of the two materials’ valence bands at the junction, which controls the open circuit voltage of the solar cell. The relative energies of ZnSe and CdTe at the interface are directly affected by the material quality of the interface through processing.
Robert Opila graduated from the University of Chicago with a PhD in Chemistry in 1982 and immediately began work at Bell Laboratories. While there, he studied the role of surfaces and interfaces in electronic materials and devices. He was named a Distinguished Member of Technical Staff and promoted to technical supervisor. In 2002 Opila joined the Department of Materials Science and Engineering at the University of Delaware, where his interest in the surfaces and interfaces of electronic materials has grown to include photovoltaics and thermoelectrics. Opila has been a member of the AVS since 1980 and has served as chair of the Applied Surface Science Division and the Electronic Materials and Processing Division. He is a fellow of the AVS and is currently an editor of Applied Surface Science. Last semester, Opila was a recipient of a Fulbright Fellowship, and lectured and studied at Bilkent University in Ankara, Turkey. He is a visiting professorial fellow at UNSW for this semester.
Wide Band Gap III-Nitride Compound Semiconductor Devices:
The Universal Solution for Energy Applications.
Dept. of Electrical and Computer Engineering
University of North Carolina at Charlotte
9201 University City Boulevard
Charlotte, NC 28223
Development of wide-band gap compound semiconductors materials and structures led by the III-Nitrides are fueling a revolution in the areas of energy related areas of lighting, solar cells, and more recently thermoelectric applications. This talk will show that the III-Nitrides can provide a possible solution for many applications were traditionally III-V materials and devices are used and, in particular, energy related applications.
Light emitting diodes (LEDs) use in lighting, also known as solid state lighting (SSL) has been very successful in niche markets such as signage and displays, but has still not seen significant penetration in the general illumination market. LEDs have advantages over conventional light sources, such as higher efficiency, longer life, smaller size, and enhanced controllability. The key limitations of the first generation SSL in general illumination such as a high color rendering capability, and appropriate correlated color temperature are being addressed in the current generation of SSL solutions. However, to achieve high quality white light gaps in the power spectrum of typical LED sources have to be eliminated. Broadband spectrally dynamic solid state illumination source comprising of a three or two terminal dual LED structure has been developed. A combination of multiple phosphors are then “pumped” by either or both of the wavelengths emitted from the dual LED to produce white light of a variable power spectrum. Such innovations will help SSL sources further increase it competitive advantage over conventional illumination sources.
The III-nitride technology is also the base in development of a new generation of highly efficient solar cells. Wide-band gap InGaN based solar cells in the 2.4-2.9 eV range for integral photovoltaic devices component are projected to achieve efficiencies greater than 50% making solar energy more feasible and competitive. InGaN with indium compositions up to 30% (2.5 eV band gap) are developed for photovoltaic applications by controlling defects and phase separation using metal-organic chemical vapor deposition. Subsequent generations of solar cell designs involve an evolutionary approach to enhance their open-circuit voltage and internal quantum efficiencies. Second generation InGaN solar cell design involving a 2.9 eV InGaN p-n junction sandwiched between p- and n-GaN layers yields internal quantum efficiencies as high as 50%; while third generation devices utilizing the novel n-GaN strained window-layer enhance the open circuit voltage of a 2.9 eV InGaN solar cell to 2 V. These results establish the potential of III-nitrides in ultra-high efficiency photovoltaics.
Some recent measurements of the thermoelectric properties–the Seebeck coefficient, the electrical conductivity and the power factor – of GaN and InGaN thin films will also be reported. GaN:Si exhibited a maximum power factor of 9.1x10-4 W/m-K with a carrier concentration of 1.6x1018 cm-3, and In0.1Ga0.9N exhibited a maximum power factor of 109x10-4 W/m-K with a carrier concentration of 1.2x1018 cm-3. The results also indicate that GaN and InGaN-based materials could potentially be useful materials for TE applications at high temperatures.
Dr. Ian T. Ferguson is a currently a Professor and the Chair of Electrical and Computer Engineering at the University of North Carloina at Charlotte. He is a Fellow of Institute of Electrical and Electronic Engineering (IEEE), Fellow of Institute of Physics (FInstP), and Fellow of the International Society for Optical Engineering (SPIE).Prior to this he has held leadership positions in both academia (St Andrews, Imperial College, Northwestern, Georgia Tech, etc.) and industry (GEC, EMCORE, etc.). His current research currently focuses on the area of wide bandgap materials and devices (emitters, detectors and electronics) using GaN and ZnO, and developing these materials for energy and nanotechnology applications in the area of illumination, solar, spintronic and nuclear detection applications. Dr. Ferguson has have authored over 400 refereed publications (current H-Index is >34), seven book chapters, eleven conference proceedings, one book and multiple patents. He has have given over 300 invited and contributed talks and seminars throughout the US, Europe and Asia. He founded the International Conference on Solid State Lighting which is now in its twelfth year. Dr. Ferguson received a National Small Business Association Award at the White House in Washington DC for contributions to the SBIR program. He was awarded a Technology Utilization Foundation Technology Transfer Award for contributions to the development of light emitting diodes. Most recently Dr. Ferguson co-founded and is the Chairman of the Board for PiES, Project for innovation, Energy and Sustainability, a non-profit green business incubator in Davidson (http://www.pies-northcarolina.org). He was selected by the Charlotte Business Journal for ‘General Excellence in Sustainable Leadership’ in the 2011 Sustainable Business Awards for this work.
Low carbon buildings – a pathway to lowering CO2 emissions.
A/Prof Alistair Sproul
Low carbon buildings are increasingly being proposed as a pathway towards reducing CO2 emissions. Utilising greater levels of energy efficiency and distributed renewable energy such as rooftop photovoltaics or Building Integrated PV, low carbon buildings provide one of the quickest and lowest cost pathways for reducing CO2 emissions. In this seminar Associate Professor Alistair Sproul will describe some of the research being undertaken with the Low Carbon Living CRC. Assoc. Prof. Sproul jointly leads the “Integrated Building Systems” research program with the LCL CRC. In this seminar he will describe some of the research being carried out in the area of energy efficient buildings and PV/T systems, including an update on the energy performance of the Tyree Energy Technology building.
Dr Alistair Sproul is an Associate Professor within the School of Photovoltaic and Renewable Energy Engineering at UNSW. He has worked in the area of photovoltaic and energy efficiency research and R&D since 1985 with various companies and research institutions. His current research interests are in the area of PV/energy systems for low energy buildings and highly efficient water/air systems. Associate Professor Sproul is a Program Leader (Integrated Building Systems) with the “Low Carbon Living” Cooperative Research Centre.
Overview of PV Activities at NCPRE, IIT Bombay
NCPRE, IIT Bombay
The presentation will be an overview of National Centre for Photovoltaic Research and Education (NCPRE) activities to date and plans ahead. The centre's structure, research and education activities, investigators, staff and facilities will be introduced. The research activities in c-Si, new materials, PV modules and systems, testing, chracterization, modelling and simulation will be summarized. The education and training programs delivered will be outlined. Our industry affiliation program and PV users program will be discussed. The presentation will also cover 1MW distributed PV power plant under implementation at IIT Bombay.
Vaman Kuber is currently advising NCPRE at Indian Institute of Technology, Bombay in development of training programs, industry outreach and PV project studies.He also advises Power Shine Energy, Bombay in development of large size PV power plants, both rooftop and utility scale. He has developed innovative solar systems solutions, consulting in solar power systems design, integration, testing and monitoring for off-grid, grid-support and on-grid applications in India. He has managed solar cell process, test and characterization equipment design and implementation projects in PV research laboratories at ANU and UNSW, Australia
Novel Photovoltaic Device Architectures for Advanced Energy Conversion
Florida Solar Energy Center, University of Central Florida
The realization of a high efficiency/low cost solar hybrid device that is easily manufacturable is one of the defining problems of photovoltaics. Real photovoltaic devices lose energy through a number of mechanisms, including electron-hole recombination, internal resistance, partial absorption, dust deposition, heating, and reflection. In this talk, specific examples of advanced PV device architectures being investigated at the Florida Solar Energy Center will be presented with the view towards high efficiency non-conventional device architectures for solar energy harvesting.
Nicoleta Hickman is currently an Associate Professor in the Solar Energy Division and the leader of the Laboratory for Photovoltaic and Thermoelectric Materials and Devices at Florida Solar Energy Center - University of Central Florida. She received a B.S. and M.S in Physics from “Al. I. Cuza” University - Romania in 1998 and 1999, respectively. She received her second MS and Ph.D. in Physics from Clemson University in 2004 and 2006, respectively. She served as a Visiting Assistant Professor in the Advanced Energy Research Division at Florida Solar Energy Center from 2006 to 2008. From 1999 to 2001 she worked at the National Museum of History from Bucharest as a physicist.
The Laboratory for Photovoltaic and Thermoelectric Materials and Devices from Florida Solar Energy Center is devoted to developing the fundamental science and engineering base required to improve PV device performance and processing technologies and to effectively transfer these laboratory results to large-scale manufacturing exploring new frontiers in manufacturing research and education. Dr. Hickman’s group performs research at the leading edge of advances in electronic, thermal and optical materials, and devices for applications in photovoltaic, thermoelectric, and solar energy integrated systems. Pushing back the boundaries of absorption and conversion efficiency for ideal solar cells and looking at how the performance of practical devices can be brought to the level of those of ideal devices, working on multi and single junction organic-inorganic solar cells with unconventional geometries, developing hybrid constructions of Photovoltaic and Thermoelectric cell to improve the solar cell efficiency and longevity, and investigating the physical properties of the solution processing transparent electrodes based on graphene and Carbon Nanotubes are the directions explored in her laboratory.
The interdisciplinary philosophy of research within her laboratory combines the disciplines of physics, materials science, chemistry and electrical engineering leading toward attractive research opportunities. The background of students and researchers within the lab reflect this breadth, and as a result, the laboratory is vertically integrated in its activities, straddling from basic to applied research.
Light management for polycrystalline silicon thin film solar cells on glass superstrates
Due to weak absorption of near infrared light and ~2μm absorber thickness, about half of the useful solar radiation is lost in thin-film poly-Si cells without light management. In this sense, light management, including light incoupling and trapping, is vital for poly-Si thin-film solar cells on glass to become competitive in the photovoltaic market. This work provides a full view of efficient light management design, which involves structuring of three interfaces: air side glass surface texturing to improve light incoupling, Si side glass surface texturing to enhance light trapping, Si film rear surface design to maximise the back reflection, therefore light trapping. The work also achieves three other objectives: (i) Assessing the light trapping capability of textured glass without depositing anything on it by developing a novel method, which facilitate glass texturing development; (ii) Improving light trapping for e-beam poly-Si thin-film solar cells to make e-beam evaporation commercially viable; and (iii) Reproducing the optimal glass texture in a well controlled and potentially cheap way— nano-imprinting. Through the methods above, a Jsc of 28mA/cm2 is attained for a ~2 μm thick cell which outperforms the record cell in the 800-1200nm wavelength range. The underperformance in the 300-800nm range mainly comes from inferior metallisation and unsatisfactory passivation.
Dr. Cui completed his PhD thesis in SPREE, UNSW with a focus on light management for poly-Si thin film solar cells on glass superstrates. His work covered nano-imprinting, glass texturing, Si texturing, AR and light trapping design, back surface reflector optimisation. He worked with Dr. Xiaojing Hao and Dr. Anita Ho-Baillie on CZTS solar cells and virtual Ge wafer projects after completion of his thesis. Presently he mainly works with Dr. Xiaojing Hao on evaporation of high efficiency CZTS solar cells.
Improving the light-harvesting of thin-film solar cells
with photochemical upconversion
School of Chemistry, The University of Sydney
Tim F. Schulze1,3,*, Yuen-Yap Cheng1, Rowan W. MacQueen1, Tony Khoury1, Maxwell J. Crossley1, Bernd Stannowski2, Klaus Lips3 and Timothy W. Schmidt1
1School of Chemistry, The University of Sydney, NSW 2006, Australia
2Competence Centre Thin‐Film‐ and Nanotechnology for Photovoltaics Berlin (PVcomB),
Helmholtz‐Zentrum Berlin für Materialien und Energie, 12489 Berlin, Germany
3Institute for Silicon Photovoltaics, Helmholtz‐Zentrum Berlin für Materialien und Energie, 12489 Berlin, Germany
Current solar cells are fundamentally limited by their inability to harvest photons with energies less than the absorber optical threshold. Thin‐film solar cells such as a-Si:H or organic solar cells, usually having band gaps above the optimum single‐band gap value of 1.34 eV given by the Shockley‐Queisser limit, and a much smaller volume to absorb the light, are particularly prone to this loss mechanism and thus suffer from imperfect usage of the solar spectrum. An elegant way towards overcoming this limitation and using a larger fraction of the incident light is the re‐shaping of the solar spectrum by upconversion (UC) of photons. Photochemical upconversion, as realized by triplet‐triplet annihilation (TTA) in organic molecules , operates efficiently from the near infrared and red part of the solar spectrum to the yellow or green, with measured quantum efficiencies of up to 30% .
Recently, we have demonstrated TTA-upconversion to improve the light harvesting of amorphous silicon and organic bulk heterojunction solar cells [3, 4]. In the present talk we will review these results, and then focus on pathways aiming to increase the photocurrent gain by TTA-UC to device-relevant levels: A first approach towards this end consists in exploiting micro-optical means for the concentration of light in the upconverting layer, which we have found to increase the solar cell photocurrent due to the inherently non-linear response of the UC yield on the illumination conditions. A second step is the transfer of the TTA-process into a solid-state medium, which will allow for a significant increase of the sensitizer dye excitation rate – and thus the UC efficiency – by concentrating the chromophores in a much smaller volume.
 Baluschev, S., Miteva, T., Yakutkin, V., Nelles, G., Yasuda, A., and Wegner, G. Phys. Rev. Lett. 97, 143903 (2006).
 Cheng, Y., Khoury, T., Clady, R. G. C. R., Tayebjee, M. J. Y., Ekins-Daukes, N. J., Crossley, M. J., and Schmidt, T. W. Phys. Chem. Chem. Phys. 12, 66–71 (2010).
 Cheng, Y. Y., Fückel, B., MacQueen, R. W., Khoury, T., Clady, R. G. C. R., Schulze, T. F., Ekins-Daukes, N. J., Crossley, M. J., Stannowski, B., Lips, K., and Schmidt, T. W. Energy Environ. Sci. 5, 6953–6959 (2012).
 Schulze, T. F., Czolk, J., Cheng, Y. Y., Fückel, B., MacQueen, R. W., Khoury, T., Crossley, M. J., Stannowski, B., Lips, K., Lemmer, U., Colsmann, A., and Schmidt, T. W. J. Phys. Chem. C , DOI: 10.1021/jp309636m (2012).
The transformation of energy systems towards sustainability – experience gained in Germany
Fraunhofer Institute for Solar Energy Systems (ISE), Germany,Solar Energy Research Institute of Singapore (SERIS), Singapore
The German parliament and the German government have decided to reduce the country’s greenhouse gas emissions by 2050 by at least 80%. Important additional milestones are to generate 35% or 80% of the electricity via the conversion of renewable energy sources by 2020 and 2050 respectively. Furthermore (later) it was decided to phase out nuclear energy conversion in Germany until 2022.
This transition of the energy supply system – in German: “Energiewende” – is in full swing. E.g. today 25% of the country’s electricity demand is generated from renewable sources (wind, solar, hydro and biomass). On the other hand the political discussion concerning in particular the distribution of the cost of the “Energiewende” is getting fierce.
From a technological point of view no principle problem hindering the transformation process has been identified. But the technological/economic optimisation of the transformation process is still an open question.
The talk will address: (i) cost reductions in electricity from renewable sources, (ii) market introduction strategies for energy from renewable sources, (iii) challenges in establishing smart grids (load and generation management, energy storage, upgrading of the energy distribution system), (iv) ideas for an optimisation of the future energy system of Germany and (v) visions on large area (inter-) continental energy supply systems.
Developments in photoluminescence characterisation for silicon photovoltaics
SPREE - Final Year PhD
Luminescence based characterisation is now used widely in both photovoltaic research and industry. The development proceeds with adding to the range of applications and exiting methods are refined. The presentation will discuss a few exciting examples from recent research including the qualitative analysis of silicon bricks and a selection of new wafer based techniques.
Bernhard Mitchell is in the final year of his PhD research at SPREE UNSW where he concentrates on the photoluminescence (PL) characterisation of silicon bricks. He developed and refined a new PL based method able to accurately image the minority carrier bulk lifetime and doping on bricks. This research was recently awarded by the Taiwanese Semiconductor Manufacturing Company (TSMC). Prior to his research at UNSW, Bernhard was a research student and associate at Fraunhofer Institute for Solar Energy Systems (ISE) in Germany. At ISE he led a project in the area of beam-splitting photovoltaics which achieved 34% non-concentrated device efficiency.
The optics of conventional solar cells and modules
This seminar describes recent advances in the characterisation and modelling of conventional solar cells and modules. These include a model for the isotexture used in multicrystalline cells; the difference between random and regular pyramidal texture; attributes of imperfect texturing; the effect of diffuse reflectance from white backsheets and isotextured silicon; measurement of the complex refractive index of EVA, solar glass, and other encapsulation materials; short-wavelength losses and their relevance to selective-emitter solar cells; luminescent down-shifting; and how the incident spectrum depends on location. Methods to simulate these effects are described and procedures to optimise a PV module’s optical design are outlined. The seminar concludes by summarising the optical models and materials that would benefit from more research.
Keith completed a PhD at the University of New South Wales in 2001. He then worked at SunPower Corporation for four years where he was a core member of the team that developed the A-300 high-efficiency rear-contact solar cell. From 2005 to 2011, he was a Research Fellow with the Australian National University, leading a research group that focused on the optics and recombination in silicon solar cells. He is now a research consultant to the photovoltaic industry and director of PV Lighthouse, which develops and hosts simulation software for photovoltaics applications. He has co-written over 100 scientific articles and patents.
Metal-oxide:polymer solar cells – experimental studies on improving device efficiency
Organic solar cells, based on organic polymers and small organic molecules, are very promising as a low cost alternative to standard photovoltaic systems. One type of organic solar cell, the Metal-oxide:polymer solar cell, combines the advantages of both the inorganic and organic components including cheap synthesis, non-toxicity, and suitable charge transport. However device efficiencies are currently low and require optimization strategies to be investigated to reach its promising potential. The incompatibility between the inorganic and organic components remains the most challenging obstacle in these devices. Some approaches that can be applied to overcome this issue include nanostructure modification of the metal-oxide, thermal processing of the polymer, molecular or inorganic modification of the interface, and other techniques. This talk will present several preliminary optimization strategies studied for the metal-oxide :polymer nanoporous solar cell focusing on TiO2 or ZnO as the metal-oxide.
UNSW SPREE - BE BSc PhD UNSW, FTS, SMIEEE, FIEAust
SOLA3020 PV Manufacturing - Trends in Photovoltaics
This is Professor Wenham's lecture Trends in Photovoltaics to 3rd year Photovoltaics students at UNSW.
1. Trends in PV Manufacturing
2. Price and Market Trends
4. Trend in Technology
5. Trend to replace Ag with Cu
6. Wafer Trends
8. Balance of System
9. Trends in Education & Training
Up-conversion for crystalline Si photovoltaics: realistic efficiency limits and enhancement in photonic structures
SPREE PhD Student (thesis submitted - PhD pending)
Up-conversion (UC) has been proposed as a means of breaking the Shockley-Queisser limit by converting the sub-band-gap portion of the solar spectrum into shorter-wavelength light. While the limiting efficiency of ideal UC-PV is lower than that of other Third Generation concepts, its simple realisation suggests that it is a viable near-term solution for commercial devices. In particular, it has been assumed that the application of a UC layer to the rear of a conventional Si solar cell---to boost its limiting efficiency to near 40%---will secure a prominent commercial position for the technology.
In this talk I will discuss the engineering challenges involved in the design of a c-Si-based UC-PV device: using a detailed balance framework, I first develop a generalised model of a 'realistic' c-Si solar cell and discuss the deviations from ideality that have an especially significant impact on UC-PV efficiency.
Second, I incorporate the substantial non-idealities of erbium-based UC layers into the model and discuss their on UC-PV device efficiency. The results indicate that it will be difficult to experimentally demonstrate increased c-Si solar cell efficiency by the application of an erbium-based UC layer without substantial improvement of the optical properties of the materials involved.
Third, I demonstrate that absorption in UC layers may be increased above the bulk value if the layer is designed to function as a one-dimensional photonic crystal. In an appropriately-designed structure, the velocity of energy propagation may slow to a crawl---tens of times slower than the speed of light in vacuum---resulting in high energy densities. Pumping optical transitions in these 'slow light modes' results in strong absorption, which may lead to higher UC-PV efficiency. I will demonstrate the calculated impact of this effect as well as experimental evidence of absorption enhancement in Si-based erbium-doped photonic crystals.
CRAIG JOHNSON received a Bachelor of Science in Electrical Engineering from the Georgia Institute of Technology in 2007 and has been at SPREE since 2008. He has just submitted his PhD and is now working on plasmonics with Dr. Supriya Pillai.
Dopant – Hydrogen Interactions in Silicon Solar Cells
SPREE PhD Student
Introduction of Hydrogen to passivate defects in Silicon solar cells is standard in most commercial cell technologies and large increases in minority carrier lifetime have been realised. In order to best utilise hydrogens ability to passivate defects the interactions between hydrogen and dopant impurities need investigation. This talk will focus the ability of hydrogen to de-activate dopants as well as the dopant concentration effects upon the mobility and charge state of hydrogen. Applications such as the emitter design of solar cells and the use low resistivity bulk wafers will be used to illustrate these interactions.
Semitransparent Organic Solar Cells
Prof Furong Zhu
Department of Physics and Institute of Advanced Materials
Hong Kong Baptist University, Kowloon Tong, Hong Kong
Compared to current silicon-based solar cells that are rigid, organic-based solar cells that use solution-based processing deposition techniques are simpler and potentially less expensive to manufacture. Organic photovoltaic cells can be made flexible, semitransparent and are light weight, offer more opportunities for application in new markets such as mobile electronics, disposable electronics, smart cards, power generating windows, smart sensors, automotive, home appliances and outdoor lifestyle etc. Its unique flexibility and semi-transparency feature also adds a decorative and aesthetic dimension to the solar cells so that it can be used on curved surface. After a brief overview of ITO-based transparent cathode, the enhancement of semitransparent organic solar cells over the two competing performance indices of power conversion efficiency and transmittance will be discussed. Our recent research progress in developing semitransparent organic solar cells will be presented.
Furong Zhu is a Professor in the Department of Physics and Institute of Advanced Materials (IAM) at Hong Kong Baptist University (HKBU). He received his BSc and MSc in Physics from Fudan University, Shanghai China, in 1983 and 1987. He completed his Ph.D in Applied Physics at Charles Darwin University in Australia from 1990-1993. He did his post-doctoral research in the Department of Electrical and Electronic Engineering at Kyoto University in Japan from 1993-1995, and was a Research Fellow with the Department of Physics at Murdoch University in Australia from 1995-1997 working on silicon thin films derived from plasma enhanced chemical vapor deposition (PECVD) for device application. He joined Institute of Materials Research and Engineering (IMRE) in Singapore in 1997. Prior to HKBU, he was a Senior Scientist and a Program Manager leading the organic light-emitting diode (OLED) and organic photovoltaic (OPV) R&D activities at IMRE. He has authored/co-authored over 90 refereed journal/conference publications, and filed 8 patents in organic electronics. His research interests include device physics, surface science, nanostructures and semiconducting materials-oriented research for application in OLEDs, OPV, thin film transistors and organic sensors. He has been invited to deliver >20 keynote/invited talks at the different international conferences.
The Association of Professional Engineers, Scientists and Managers of Australia is a Professional Association and Registered Trade Union representing engineers, scientists, computing and information technology professionals, pharmacists, architects and veterinarians.
We will be speaking at your university throughout the year, providing you with information and advice on employment issues relating to your chosen profession.
Topics include a practical insight into aspects of professional employment by covering:
We will talk to you about your transition from university to full time employment, providing you with realistic expectations and ensure that your employment prospects are not limited.
If you have any questions, please call Paul Grainger on 9263 6521.
Modelling electronic transport and confinement in nanostructures
Improving solar cell efficiency beyond the Shockley-Queisser limit and towards the thermodynamic limit can be realised through third generation photovoltaic concepts. Two major strands of research in third generation photovoltaics are Hot Carrier Solar Cells (HC-SC) and tandem solar cells. A HC-SC achieves high efficiency by preventing the thermalisation of electrons and holes to the band edge. Electrons are kept “hot” by a Hot Carrier Absorber while these “hot” electrons are extracted with the help of Energy Selective Contacts (ESC). Double Barrier Structures (DBS) with their resonant tunnelling features are ideal candidates for ESCs. A tandem cell is an optically (and often electrically) connected stack of solar cells where each cell is optimised to a particular wavelength of light. The bandgap modification required for this can be obtained by stacking different materials or by modifying the bandgap of a single material using nanocrystals of different sizes. An all-silicon tandem cell employs the latter method. In both cases, nanostructures like quantum dots (QDs) and quantum wells (QW) are used, exploiting their quantum mechanical properties, to modify the optical and electrical properties according to our requirements. Modelling quantum mechanical properties of nanostructures helps to understand, analyse and predict their macroscopic behaviour. In this presentation, I will talk about the theory of ESCs and nanocrystal based tandem solar cells and the ways to model their quantum mechanical features. Simulation results from QD and QW structures used in solar cells will be presented. In particular, the impacts of imperfections on conduction and resonant tunnelling observed from optically assisted IV measurements will be discussed.
Binesh Puthen-Veettil is a postdoctoral fellow in the School of Photovoltaic and Renewable Energy Engineering, UNSW. He is currently working in silicon tandem cell and hot carrier solar cell project. He finished his PhD from UNSW last year.
Photovoltaics: Technology Trends and Future Perspectives
Adam Shor - Senior Project Engineer & Innovation Scout
Electric Power Research Institute, USA
Significant progress has been made in the last two years in efficiency improvement and cost reduction for commercially available photovoltaic technologies. These improvements have been made as a result of research progress and the desire to capture the potential economic opportunity that cost competitive solar electricity provides. This presentation will examine the current state of play for the global solar industry, the commercially relevant technologies by market share, overall cost and market trends, and the various motivations of the different industry stakeholders. In addition, we will discuss potential improvements of power electronics for PV, innovative approaches for lowering the levelised cost of electricity, and likely scenarios for the global PV sector going forward.
Adam Shor is a Senior Project Engineer at the Electric Power Research Institute (EPRI). His research activities focus on understanding the current state of photovoltaic technology, evaluating cost & market trends, and identifying future innovations. He currently serves as the Innovation Scout for Photovoltaics, developing a global network of PV stakeholders to provide insights into the current and future state of PV technology adoption.
In addition to his work on photovoltaics, his research focuses on assessing the environmental aspects of renewable energy in order to minimize and resolve the potential environmental constraints of renewable energy deployment. This work involves developing and testing mathematical models to manage impacts on endangered and protected species, characterizing and forecasting renewable fuel resources, and identifying and managing utility concerns about renewable energy.
Prior to joining EPRI, Shor was a sustainability engineering consultant at Cundall Engineering in Australia. While at Cundall, he managed several Green Star certification projects, including a major renovation project in downtown Sydney utilizing state-of-the-art sustainability and commercial energy efficiency strategies to achieve Australia-leading carbon and water reduction targets.
Shor received a Bachelor of Arts degree in physics from Austin College. He received a Master of Engineering Science degree from the University of New South Wales, with a specialization in photovoltaics and solar energy. Most recently, he has completed the Program in Innovation and Entrepreneurship at the Stanford Graduate School of Business.
Resonant light trapping in ultrathin films: Boosting the efficiency of a-Fe2O3 photoanodes for water splitting
Department of Materials Engineering,
Technion – Israel Institute of Technology, Haifa, Israel
Semiconductor photoelectrodes for efficient solar hydrogen production by water photoelectrolysis must employ stable, non-toxic, abundant and inexpensive semiconductor visible light absorbers. Iron oxide (a-Fe2O3) is one of few materials meeting these requirements, but its poor transport properties present challenges for efficient charge carrier generation, separation, collection and injection. Here we show that these challenges can be addressed by means of resonant light trapping in ultrathin films designed as optical cavities. Interference effects between forward and backward propagating waves enhance light absorption in quarter-wave or, in some cases, deeper sub-wavelength films, amplifying the intensity close to the surface wherein photogenerated minority charge carriers (holes) can reach the surface and oxidize water before recombination takes place. Our approach enables efficient light harvesting in a-Fe2O3 films thinner than 50 nm, thereby suppressing the recombination loss and overcoming the tradeoff between light absorption and charge collection efficiencies. We show that water photo-oxidation current densities as high as 4.8 mA cm-2 may be achieved in simple stratified structures comprising ultrathin a-Fe2O3 films on a reflective substrates.
Avner Rothschild is an associate professor at the Department of Materials Engineering of the Technion – Israel Institute of Technology. After graduating from the Technion (BSc in Physics and in Materials Engineering in 1997, PhD in 2003) he spent three years at MIT as a postdoc in Harry Tuller’s group. In 2006 he returned back to the Technion as a faculty member. Avner is heading the Electroceramic Materials & Devices research group, working on semiconducting, ionic and mixed ionic electronic conducting oxides for applications in electronic and optoelectronic devices, gas sensors and solar cells. He is a member of the editorial board of the Journal of Electroceramics, the Technion Energy Team, and Israel’s Solar Fuels Consortium.
Testing the limits of experimental design
Dr. Paul Basore
Hanwha Solar America
Abstract: Design of Experiments (DoE) claims to squeeze much more information from a limited series of experiments than is possible by uniformly exploring the parameter space of interest, especially in the presence of uncontrolled variability. The theory behind this advantage assumes that the measurable results depend on the experimental factors in a smoothly continuous manner and that the uncontrolled influences obey the normal probability distribution. In reality, an experiment conducted in an early-stage investigation often spans a parameter space that includes unexpected "cliffs", and experiments conducted in late-stage optimisation often involve probability distributions that are asymmetrical due to bumping up against physical limits. Simulating the outcome of designed experiments in both of these regimes illustrates both the benefits and limits of DoE in the presence of these non-ideal effects.
Paul Basore’s twenty-five years in photovoltaics have spanned university, government and industrial positions across three continents. Since receiving his PhD in electrical engineering from MIT thirty years ago, he has managed the establishment of five PV R&D facilities. The first of these, at Sandia National Labs in Albuquerque, set the world record for multicrystalline-silicon module efficiency, a mark that was not eclipsed until 15 years later. His next facility was the pilot line for Pacific Solar in Sydney, which led to the establishment of the CSG Solar factory in Germany, where he was the founding CTO. After moving to the San Francisco Bay Area in 2007, Paul established a PV R&D lab for the Renewable Energy Corporation of Norway, and this year he completed the establishment of a PV R&D lab for Hanwha, a large and diverse Korean company that is also one of the world's top-ten PV manufacturers. In his spare time, Paul has developed some useful software, including PC1D and PC2D.
Past and projected trends in Australian PV uptake
Dr Muriel Watt
The past and projected trends in Australian PV uptake and costs will be discussed, and the road to grid parity examined for different PV market segments. Issues now arising in energy markets due to the uptake of PV, energy efficiency and demand management will be raised, and the need for a new Distributed Energy Market in Australia will be discussed..
Muriel Watt is a part-time Senior Lecturer in the School of Photovoltaics and Renewable Energy Engineering, University of NSW, Chair of the Australian PV Association and Head, Energy Policy & PV for renewable energy consulting company IT Power Australia. She also holds the positions of Australian representative on the Executive Committee of the International Energy Agency PV Power Systems Programme, member of the Australian Solar Institute Research Advisory Committee and of the Enterprise Connect Clean Technology Advisory Committee.
Dr Watt has worked in government energy agencies, private companies and universities on energy related matters since 1980, with a strong focus on renewable energy research, development, technologies, deployment and policies.
LIP, FIP and Other Good Stuff
Screen printing has been a staple process since the advent of large scale solar cell manufacturing. However with large scale manufacturers wanting to produce 20% efficient solar cells at high volume and low cost, a move towards new novel cell structures, that are largely incompatible with screen printing, is becoming paramount. This is further reinforced with reductions in the price of silicon showing few signs of stopping and forecasts that a price of $25 per kilo of silicon is sustainable in the long term and not a temporary drop. This has the solar industry now focusing on the second most costly component, the silver in the metal contact. All these events point to the need for alternative metallisation techniques.
The most promising approach capable of replacing screen printing is metal plating. There are a range of different types of metal plating and at UNSW we have been working on developing a set of metal plating processes that will enable us to form metal contacts to any silicon solar cell structure you could imagine. During this talk I will review the current state of play of metal plating, discussing the advantages of new light-induced plating methods and introducing the use of field induced plating for the metallisation of p-type silicon surfaces.
Hot carrier solar cell modelling: phonons and the light absorbing material
The Hot Carrier Solar Cell (HCSC) is a very challenging third generation concept that addresses thermalization loss in photovoltaic cells. It relies on a number of difficult fundamental physical mechanisms such as electron-electron scattering, electron-phonon scattering and phonon decay. The presentation will include a discussion of these physical mechanisms relevant to the hot carrier solar cell, designed for a general audience. The focus will be on the light absorbing material and the role phonons play in the HCSC concept.
To date at UNSW the approach explored to increase hot carrier lifetimes has been to increase phonon lifetimes. High energy or “hot” charge carriers are created when photons with energy greater than the bandgap of a semiconductor are absorbed. These hot carriers relax rapidly to the conduction band edge, typically losing energy through the emission of phonons. If these phonons are long lived then the charge carriers have a greater chance of re-absorbing their energy and remaining “hot” long enough for extraction. To prevent phonon decay, materials for the light absorbing layer with the appropriate vibrational properties must be found. These are determined by computing the phonon bandstructure, which is the vibrational analogy of the more familiar electronic bandstructure. This has been done for periodic nanostructured materials such as model quantum dot superlattices in a variety of geometries and III-V quantum dot systems of the Stransti-Krastinov type. Phonon lifetimes can be assessed in some cases directly from the phonon bandstructure or by an additional calculation. The framework for developing a comprehensive model of hot carrier cooling in arbitrary materials will also be shown.
Presentation of INES, the French National Institute for Solar Energy: overview of the wide R&D range: from solar grade to sustainable building and electric cars.
Dr. Francoise Burgun
Presentation of INES, the French National Institute for Solar Energy: overview of the wide R&D range, from solar grade to sustainable building and electric cars.
INES is the first French and one of the first European centres dedicated to research, innovation and training on solar energy. Set up with the backing of the French Government, the Regional Council and staffed by teams from the CEA (Atomic Energy and Alternative Energy Commission), the CNRS (National Centre for Scientific Research), and the University of Savoie, it gathers today more than 350 people from different backgrounds and by the year 2015 will bring together more than 500 people onsite 20,000 sqm.
INES is a young institute as it began to take shape in 2005 and was officially launched in July 2006. Still its achievements are remarkable through the implementation of a wild range of technological platforms, as well as its capacity to attract high qualified and experienced engineers and researchers and its ability to launch many academic and industrial research programs on a national and international level.
The CEA staffs of INES – DTS, Department for Solar Energy - count more than 300 employees and therefore constitute the main task force for INES Research and Innovation activities. They cover the fields of solar thermal, photovoltaic, energy storage and their application to the domain of energy, building and electric car. DTS’s research work covers complete technological processes, from basic components to prototypes integrated into a system for the purposes of demonstration. Its approach to research takes into account the need for quick turn-around times and constraints on industrial costs.
Moreover, DTS is part of the LITEN, the Laboratory for Innovation in New Energy Technologies and Nanomaterials of CEA, which is one of Europe’s newest and most important research centres in the energy technology field. Hence, DTS strengthens its capacity trough access to latest LITEN’s advanced researches on materials and energy managemen
Classification and Investigation of Recombination Active Defects in Multicrystalline Silicon Solar Cells
All multicrystalline silicon (mc-Si) solar cells suffer from recombination active defect structures. Recombination active defects in solar cells made from pure as well as from upgraded metallurgical grade Si feedstock are limiting the solar efficiency and electrical breakdown behaviour. Therefore it is of utmost importance to understand the cause and the physical mechanism of recombination and pre-breakdown processes at these defects. Since a mc-Si solar cell has a large number of defects it is mandatory to classify the different defect before investigation. In this seminar a classification of recombination active defects in mc-Si solar cells based on previous studies is presented. Two types of recombination active defects can be clearly distinguished already on a macroscopic scale. For a more detailed understanding the classification was also performed on microscopic scale. It is shown that defect types observed on a macroscopic scale could also be directly related to structures on a microscopic scale; however, a third defect type had to be introduced. The microscopic investigations allow us to establish an exact relation of electrical, structural and chemical information. One defect type could be clearly correlated to metal precipitates located at defect structures of the underlying wafer explaining additionally the observed pre-breakdown behaviour at these defect structures. It is also shown that this defect type is strongly influenced by the solar cell process. Based on these results a model for the different classified types will be proposed explaining the observed recombination and pre-breakdown behaviour. The knowledge obtained can be reversibly interconnected to the macroscopic investigation on an industrial level to work on a solution to avoid these problems.
2012 SEMI Roadmap for Photovoltaics: Bigger, Thinner, Faster, Cheaper
Scientia Professor Martin Green
Industry roadmaps have played a major role in the microelectronics industry in focussing manufacturers, researchers and equipment suppliers on common targets for future technology development. In 2010, the first roadmap for the photovoltaics industry was published, with a major update published recently at the end of March 2012. The key features of the new roadmap will be described. Particularly interesting are variations from the previous 2011 roadmap as these indicate refinements in thinking about the future of the industry based on the very rapid progress over the last year.
Martin Green is currently a Scientia Professor at the University of New South Wales, Sydney, Australia and Executive Research Director of the University's Photovoltaic Centre of Excellence. His group's contributions to photovoltaics include development of the world’s highest efficiency silicon solar cells and commercialization of several different cell technologies. He is the author of several well known books on solar cells and numerous papers. His work has resulted in many major international awards including the 2002 Right Livelihood Award, commonly known as the Alternative Nobel Prize, the 2007 SolarWorld Einstein Award and the 2009 ENI Award for Renewable and Non Conventional Energy.
Harvesting Solar Energy Using Nanofluids-Based Concentrating Solar Collection
Dr. Himanshu Tyagi
Conventional concentrated solar thermal collectors harness solar energy through several steps of heat transfer. The incident solar radiations are usually directly absorbed by a solid surface (either flat, in the case of a flat-plate type solar collector - or curved, in the case of parabolic trough collectors). These surfaces in turn can transfer the thermal energy to a fluid which may then be used for various applications such as for process heating, chemical processing, electricity generation etc. For some years now, research work has been going on to make the heat transfer process more efficient primarily by reducing the heat losses from a solar collector. One unique way this can be achieved is by employing the concept of direct absorption where a significant portion of the sunlight is directly absorbed by the fluid itself - thereby eliminating one big step of heat transfer.
In order to achieve direct absorption, trace amounts of nanoparticles may be added to the base-fluid which is shown to have significant impact on the optical as well as thermo-physical properties of the base fluid. Enhancement of thermal conductivity and absorption capacity of the base fluid scales up the heat transfer rate. This results in higher & more efficiency heat transfer. Preliminary results have shown that while maintaining the same external conditions (such as ambient/initial temperatures, wind speed, solar insolation, flow rate, concentration ratio etc.) the nanofluid-based parabolic concentrating solar collector has about 5-15% higher efficiency as compared to the conventional parabolic solar collector.
Himanshu Tyagi is currently working as Assistant Professor in the School of Mechanical, Materials & Energy Engineering at Indian Institute of Technology (IIT) Ropar. He has previously worked in the Steam Turbine Design Division of Siemens (in Germany & India) and in the Thermal & Fluids Core Competency group of Intel (in USA). He did his PhD from Arizona State University in the field of heat transfer, and specifically looked at the radiative & ignition properties of nanofluids. He and his co-workers proposed the concept of direct absorption solar collectors using nanofluids which won the Best paper award at the ASME Energy Sustainability Conference at Long Beach, CA. Prior to his PhD he obtained his masters from University of Windsor, Canada and his bachelors from IIT Delhi both in Mechanical Engineering. At present he is working to develop clean and sustainable energy sources with a team of three graduate students and four undergraduates.
VALUE OF PHOTOVOLTAIC SOLAR CELL EFFICIENCY TO ACHIEVE LOW COST SOLAR ELECTRICITY
Professor Allen Barnett
The levelized cost of energy (LCOE) is used to compare different energy generation technologies or systems. The relatively high LCOE of photovoltaics (PV) can be an obstacle to adopting it as a significant electricity source for terrestrial applications. In a conventional PV system, the cost of the module contributes approximately half of the expense and the other costs are together summarized as balance of system (BOS). A large portion of the BOS is not related to the peak power of the system, but can be either proportional to or independent of the total installation area. Across different PV systems with the same installation area, this part of BOS ($/W) is directly dependent on the module efficiency. Therefore, the LCOE is affected by the module efficiency even if the module price ($/W) remains the same. In this paper, the LCOE across PV systems with equal installation areas but with modules of different efficiencies installed with fixed tilt, 1-axis tracking or 2-axis tracking are compared. It is concluded that at a given module price in $/W, more efficient PV modules lead to lower LCOE systems. Two examples of new high efficiency solar cell modules; thin crystalline silicon (20+%) and tandem solar cells on silicon (30+%) will be presented.
Allen Barnett joined the School of Photovoltaics and Renewable Energy Engineering, The University of New South Wales, Sydney NSW 2052 Australia as Professor of Advanced Photovoltaics in September 2011. At UNSW his research is focused on new high efficiency solar cell modules; thin crystalline silicon (20+%) and tandem solar cells on silicon (30+%). He joined the University of Delaware in 1976 as Director of the Institute of Energy Conversion and Professor of Electrical Engineering. He left UD in 1993 to devote full time to AstroPower, Inc, which became the largest independent solar cell manufacturer and the 4th largest in the World. He returned ot UD in 2003 and was Executive Director, Solar Power Program; Research Professor, Department of Electrical and Computer Engineering; and Senior Policy Fellow, Center for Energy and Environmental Policy at the University of Delaware, Newark Delaware. Barnett has supervised 26 Ph.D. theses including 7 Ph.D.s and 3 M.S. degrees in 2011.
Barnett received his M.S. and B.S. in Electrical Engineering from the University of Illinois, and his Ph. D. in Electrical Engineering from Carnegie-Mellon University. He is a Fellow of the Institute of Electrical and Electronic Engineers (IEEE). He received the IEEE William R. Cherry Award for outstanding contributions to the advancement of photovoltaic science and technology and the Karl W. Böer Solar Energy Medal of Merit. He is on committees for the two largest photovoltaic conferences. He has more than 280 publications, 28 U.S. patents, and 7 R&D 100 Awards for new industrial products. He actively consults for government agencies, institutional investors, and private companies. He was named one of “The 50 Most Influential Delawareans (State of Delaware) of the Past 50 Years” in 2012
TUV Rheinland Japan – Experience through global growth of the PV Industry and the role of Quality Assurance in enabling development of Solar Energy.
TUV Rheinland, with the largest global network of PV testing laboratories and over 30 years of experience in the field of photovoltaics, has been assisting the PV industry on its path to becoming a major contributor to the world energy mix. Solar photovoltaic power has become an economical and attractive energy form within this energy mix, while manufacturers try to maintain strong positions facing an increasingly competitive market.
After the March 11 earthquake over 40 nuclear power stations were disconnected from the grid due to safety concerns. In order to address this energy supply problem the Japanese government has redesigned its energy policy and plans to introduce a strong feed-in-tariff for PV within this year which will also support large mega-solar installations. With such potential for growth, quality assurance and 3rd party testing has never been more important in order to ensure the confidence of investors and the public in photovoltaic energy. With our master solar testing laboratories for the Asia/Pacific region, TUV Rheinland Japan is in a key position to help enable safe and reliable roll-out of photovoltaics at a large scale.
This seminar will introduce testing and evaluation procedures for photovoltaic modules while describing general operations of TUV Rheinland as a group, with particular insights into our Japan photovoltaic testing laboratories where several UNSW students have participated in our internship program!
Nick Morley, BE RE Eng, Honours Class 1
TUV Rheinland Japan
Hot Carriers Solar Cells:
Recent developments and future challenges
The hot carrier solar cell is a third generation photovoltaic device that can potentially achieve a conversion efficiency well above the Shockley-Queisser limit by limiting heat loss, which is the main cause for the limited efficiency of conventional solar cells. This can be accomplished by extracting highly energetic (hot) carriers from the absorber layer of the device before they thermalise by losing their excess energy to the absorber lattice as heat. Although the basic operating principle of a hot carrier solar cell is rather simple, the actual design and realization of the device presents complex theoretical and technological challenges.
This seminar has the aim of giving an overview of current research on hot carrier solar cells, presenting recent achievements and future challenges that need to be addressed in order to move towards the realization of a device. Furthermore, results of theoretical and experimental work on practical hot carrier solar cell structures performed at UNSW will be presented and discussed.
Diode Laser Processing of Si Thin Film Solar Cells
This seminar presents three new processes utilising a fast, large area cw diode laser to improve the efficiency and reduce the cost of silicon thin-film solar cells made on glass substrates.
The first is a defect annealing process which replaces a belt furnace anneal for the removal of crystallographic defects and activation of dopants in solid-phase crystallised silicon. The highest substrate temperature required during the process sequence is reduced from 960C to 620C, which opens the door to the use of cheaper glass substrates. A peak 1-sun voltage of 492mV is achieved on planar samples, which is an improvement of 32mV over the belt furnace process.
The films are shown to be partly recrystallised during the process, significantly improving the material quality of the melted section while retaining the dopant profile within the un-melted section.
Completed devices are shown to match the performance of the optimised belt furnace process.
The second is a complete laser crystallisation process applied to thick a-Si films. Here the film is molten across the entire thickness, and a regime is found whereby long linear grains are formed by continuous growth with the previous crystallised region acting as a seed for thenewly crystallising material.
Grains up to millimetres in length and hundreds of microns in width have been grown with virtually zero detectable intra-grain defects.
A rear diffused emitter is used to create a pn junction, which produces voltages as high as 539mV so far.
IQE measurements show that the glass-side of the films is very well passivated and that the diffusion length is much longer than the device thickness.
Cells up to 7.8% efficiency have so far been demonstrated without light trapping or optimisation of many of the key processes.
The third new process is large area solid-state diffusion using a diode laser to drive in spin-on dopants.
This process has been used to form a junction and demonstrated some of the highest voltages on the diode laser crystallised silicon and to form a back surface field for solid-phase crystallised cells
20% Double-sided Laser-doped Cells on Standard
Commercial Grade P-type Silicon
This seminar presents the development of a novel next-generation Laser-doped Selective Emitter (LDSE) cell structure that focuses on improving the rear surface design while retaining the excellent front surface design of the LDSE cell. This cell structure employs a commercially-manufacturable dielectric layer for rear surface passivation; and relies on the use of boron laser doping in conjunction with sputtered Al for localised rear contact formation. Test structures with an implied Voc over 700 mV (prior to laser doping) indicates high surface-passivation quality given by the dielectric layer following thermal anneal. Demonstration of sheet resistance as low as 5 W/ on the boron laser-doped p+ regions highlights the potential for low-temperature Al sintering to form an ohmic contact. Different geometries for the rear contact pattern are designed and implemented to establish optimum current collection. By improving the rear surface design, cells with independently-confirmed cell efficiencies as high as 20% are achieved on large area, standard commercial-grade p-type wafers, with the potential for further efficiency increase exceeding 21%. These results suggest that this new-generation of LDSE cells have the potential of becoming an industrially-applicable cell technology in the PV industry.