Technical Program

TUTORIAL 2: Silicon Cell and Module Testing: Best Practice for Silicon R&D and Production

Instructors: Ronald A. Sinton , Sinton Instrument, Boulder CO USA
Johnson Wong, Vancouver, BC Canada

This tutorial will discuss cell and module testing. A particular emphasis will be placed on best practice for testing Silicon devices under industrial conditions, at calibration laboratories, and in R&D. Strategies for minimizing uncertainties will be presented, based on the fundamentals of the equipment and also the device physics behind concepts such as the effects of cell capacitance, illumination non-uniformity, cell mismatch, and the module circuits including bypass diodes. The ambiguities in measuring the “efficiency” of cells with vanishingly little Ag in the busbars is an especially-challenging reality. The use of production IV testing to implement cell-by-cell advanced diagnostics and process control correlated with in-line measurements will be described.

Ron Sinton did his PhD work at Stanford University developing 28%-efficient silicon concentrator cells and 23% efficient backside-contact one-sun cells. He then continued this work by adapting the fabrication processes to be more industrial as a founding member of SunPower Corporation. After founding Sinton Instruments in 1992, he focused the company on bringing the systematic device physics approach that was used to develop very high-efficiency silicon solar cells to the design of test and measurement instruments for the broader Silicon field. He was involved in the development of many techniques that are commonly used today, such as the Suns-Voc technique and the methodology for extracting and reporting implied voltage from lifetime data. Sinton Instruments provides metrology for nearly all of the research labs and production facilities working in silicon PV technology. Ron enjoys blurring the boundaries between metrology and device physics in order to report parameters that are key inputs to physical models. He participates in conference program organization, especially the IEEE PVSC (1987-2008) and the annual NREL Silicon Workshop (1994-present). Ron received the Cherry Award at the 2014 IEEE PVSC.

Johnson Wong is senior physicist at Aurora Solar Technologies, Canada, a company which offers inline tools and softwares for the measurement, visualization and control of critical processes during solar cell manufacturing. Johnson previously headed the PV characterisation group at the Solar Energy Research Institute of Singapore (SERIS), where he created various analytical tools to delineate the factors that contributed to solar cell power loss. He is the inventor of Griddler computer programs that apply full area, two-dimensional finite element analysis (FEA) to solar cells with arbitrary metallisation geometries; and Module, a finite-element simulation program for solar panels.

TUTORIAL 3: Silicon PV technology: from Cradle to Grave

Instructors: Anastasia Hertanti Soeriyadi, UNSW
Udo Romer , UNSW

SThis tutorial will begin with a brief introduction on what is needed to make a solar cell out of a semiconductor, thereby briefly explaining the basics of photovoltaics. We will then show different strategies to make a good solar cell, introducing surface passivation, light trapping, local contacts and local doping, always using typical Si solar cell structures as examples. From this we will go on looking into making really good Si solar cells by using passivating contacts and interdigitated back contact (IBC) schemes. This will then be topped by analyzing the potential of multi-junction cells on Si.

In the second section of this tutorial, we will look a bit closer at Si solar cells currently in production and the latest trends in the industry, such as structural diversification, increasing number of busbars, making solar cells bifacial, using half cells and shingling. We will further give an overview of the importance of field performance and reliability, covering different degradation mechanisms and the importance of considering the complete lifecycle of silicon PV modules for sustainability.

Anastasia Hertanti Soeriyadi is currently a Post-doc at the School of Photovoltaic & Renewable Energy Engineering at UNSW Sydney. She received her Ph.D. in Photovoltaics and Solar Energy Engineering from UNSW Sydney where she focused on the fabrication and characterization of III-V tandem solar cells on Si substrate. She is currently working on the improvement of heterojunction performance through defect engineering processes. She is also actively involved in III-V on Si projects for high-efficiency and possible industrial application.


Udo Römer is currently a Post-doc at the School of Photovoltaic & Renewable Energy Engineering at UNSW Sydney. He received his PhD in Electrical Engineering from the University of Hanover in Germany. He likes working on high efficiency Si solar cells and his research is primarily focussed on poly-Si contacts, IBC solar cells and doping processes. He also worked on electro-plating, surface passivation and optical modelling



Silvana Ayala Pelaez is a Post-doc at the National Renewable Energy Laboratory, working with the Performance & Reliability group on bifacial silicon technology. She has a PhD in Electrical and Computer Engineering from the University of Arizona. She also has a M.S. in Optical Sciences at the same University. She received a B.S. in Mechatronics Engineering from Monterrey Tec (ITESM 2007). Current projects are focused on bifacial photovoltaic performance and modeling. Her research includes characterization and energy/optics simulation for bifacial and previously for pv-holographic system energy production. She edited and published the book “Solar Outreach Handbook” in 2018.

TUTORIAL 4: Utility-Scale PV Plants, Storage and Grid Integration

Instructor: Dr. Mahesh Morjaria, First Solar, USA

Several key factors have enabled utility-scale solar generation to be both cost-effective and commercially viable. Apart from a dramatic improvement in PV module cost, these factors include plant system design, BOS component selection as well as grid interconnection capability required to deliver a fully permitted and compliant solar system. The system design, including selection of optimal DC/AC ratio, row spacing, tracking or fixed tilt mounting is focused on reducing LCOE (Levelized Cost of Energy) that maximizes the project revenue and makes it financeable.

Meeting regulatory and contractual requirements also plays a critical role in the viability of utility-scale plants. The capability of utility-scale PV plants to address grid reliability and stability concerns is critical to integrate large amounts of PV generation into the electric power grid. PV plants with “grid-friendly” features such as voltage regulation, active power controls, and ramp rate controls have successfully alleviated these reliability concerns. More recently, the ability of PV plants to provide essential grid reliability services was demonstrated. It has been shown that PV Plants even out-perform conventional generation in providing services such as frequency regulation.

As solar penetration increases further, grid operators face new challenges in managing the variable nature of solar electricity and maintaining grid balance between supply and demand. During low load periods in spring and fall, there is often more midday solar electricity produced than can be incorporated into the grid. In the evening when the sun sets and solar production decreases, other generation needs to rapidly ramp up to meet the increasing demand. Recent advances have shown that solar can provide cost-effective flexible capability that enables operators to more effectively manage resources to maintain grid balance during daytime and early evening transitions. With the addition of storage, solar can even provide firm capacity that can be dispatched as needed – just like a conventional generation plant.

This tutorial provides a high-level view of utility-scale PV system design, equipment selection, as well as a discussion of various plant optimization approaches that makes the plant viable. It also includes a discussion of several factors that have made significant PV growth possible. Next insights into practices that are necessary to meet current and future grid integration challenges will be discussed. Finally, the tutorial provides guidance on factors that make the combination of solar and storage more effective in addressing challenges arising from increased solar penetration. Dr. Mahesh Morjaria is the VP for PV Systems Development at First Solar. He leads the R&D effort in PV systems technologies for utility-scale solar plants. Over the past nine years, he has established himself as a leading expert in the area of solar generation and in addressing key challenges associated with integrating utility-scale solar plants into the power grid. Dr. Morjaria previously worked at GE for over twenty years where he held various leadership positions including a significant role in expanding the wind energy business. He brings more than 35 years of advanced technology, and product development experience. He is the author of numerous industry leading papers and patents in the area of solar, wind generation & grid integration. His academic credits include B.Tech from IIT Bombay and M.S. & Ph.D. from Cornell University.

TUTORIAL 5: Bottom-up manufacturing costs analysis of the PV module supply chain and the economics of PV systems coupled with storage

Instructors: Michael Woodhouse, NREL Brittany Smith, NREL Robert M. Margolis , NREL Kelsey Horowitz , NREL

This tutorial will review the methodology and most recent results of solar and storage technoeconomic analysis at the National Renewable Energy Laboratory's (NREL) Strategic Energy Analysis Center (SEAC). From bottom-up component manufacturing costs to project levelized cost of energy (LCOE) and levelized cost of storage (LCOS), this tutorial will provide an opportunity to review the economics and cross-technology competitiveness of solar and storage systems.

We will begin with an overview of the 2019 benchmark input data used to inform NREL’s crystalline silicon (c-Si) and thin film PV module manufacturing cost models. The accounting framework that we follow and that will be reviewed during this tutorial provides a methodology to prepare cost models in accordance with the Generally Accepted Accounting Principles (GAAP) and the International Financial Reporting Standards (IFRS). We will review input data and methods useful for calculating the costs of goods sold (COGS); research and development (R&D) expenses; and sales, general, and business administration (S, G, &A) expenses for the polysilicon, wafer, cell conversion, and module assembly steps of the c-Si supply chain, and for thin film modules. This 2019 benchmark analysis is compiled for state-of-the-art polysilicon-to-module manufacturing facilities located across the globe.

We will also show our industry-informed 2019 benchmark capital costs and levelized cost of energy (LCOE) analysis for PV systems, and our first results for levelized cost of storage (LCOS) over a range of hour durations. Next generation technologies that lower manufacturing and installation costs, reduce operations and maintenance (O&M) expenses, and improve system energy yield will also be highlighted. We look forward to sharing NREL's extensive work in these areas and discussing ideas for future directions.

Dr. Michael Woodhouse is a senior analyst within the National Renewable Energy Laboratory's (NREL) Strategic Energy Analysis Center (SEAC). His analysis activities are focused on solar energy and storage technologies, economics, and policy. He also serves as Associate Editor for the American Institute of Physics peer-reviewed Journal of Renewable and Sustainable Energy. In this role he is responsible for selecting and coordinating publications related to energy economics and policy. Dr. Woodhouse and Dr. Smith also co-lead technoeconomic analysis for the DuraMAT Consortium, which is a program of U.S. university and national lab research funded by the U.S. Department of Energy Solar Energy Technologies Office (SETO) and administered by NREL.

Dr. Robert M. Margolis is a senior energy analyst in the Washington, D.C. office of the National Renewable Energy Laboratory (NREL). Since joining NREL in 2003, he has served as the lead analyst for the Solar Energy Technologies Program as well as the lead analyst for cross-cutting analysis for the Department of Energy's Office of Energy Efficiency and Renewable Energy. His main research interests include energy technology and policy; research, development, and demonstration policy; and energy-economic-environmental modeling. Previously, he was a member of the research faculty at Carnegie Mellon University and a research fellow at Harvard. He holds a B.S. in Electrical Eng from the Univ. of Rochester, an M.S. in Technology and Policy from MIT, and a Ph.D. in Science, Technology, and Environmental Policy from Princeton.

Dr. Brittany Smith is an energy analyst in the Washington, D.C. office of the National Renewable Energy Laboratory (NREL). Her areas of expertise are in solar photovoltaic device engineering, life cycle assessment, techno-economic analysis, and PV manufacturing supply chains. Prior to joining NREL, she was a graduate fellow through the NASA Science and Technology Research Fellowship. She received her Ph.D. in sustainability from the Rochester Institute of Technology in 2018, and an honors B.A. in chemistry from the University of Delaware in 2011

Kelsey Horowitz is a researcher at the National Renewable Energy Laboratory, where she conducts techno-economic analysis of an array of photovoltaic and other clean energy technologies. Her work has included cost and market assessment of both emerging and established thin-film and concentrator PV modules as well as different strategies for integration of distributed energy resources onto the grid. Prior to coming to NREL, Kelsey researched optics, device designs, and economics of PV at the California Institute of Technology, where she received her Master’s Degree in electrical engineering. She also holds a BS in electrical engineering from the University of Colorado at Boulder.]

TUTORIAL 6: Reliability and Durability of Photovoltaic Modules

Instructors: John Wohlgemuth, PowerMark Corporation

This tutorial will describe field experiences with PV modules and how identification of failure modes can lead to the development of accelerated stress tests that are used to develop more reliable and durable products. Proper application of these stress tests through qualification testing along with implementation of quality management systems in module manufacturing led to improvements in module lifetimes and extensions of the product warranties. The tutorial will review recent research being done to improve reliability and durability with an ultimate goal of try to develop a method of assessing module lifetimes

John Wohlgemuth is the Executive Director of PowerMark Corporation and the Technical Advisor to the US TAG for IEC TC82, the PV Technical Committee of IEC. Dr. Wohlgemuth retired from NREL in 2017 after 6 years of work on PV reliability and standards. Before that he spent 34 years in the PV industry at Solarex and BP Solar. Dr. Wohlgemuth has been an active member of working group 2 (WG2), the module working group within TC-82, the IEC Technical Committee on PV since 1986 and was the convenor of the group for more than 15 years.

TUTORIAL 7: Hybrid Tandem Solar Cells

Instructors: Prof. Tyler J. Grassman , The Ohio State University
Prof. Michael D. McGehee , University of Colorado Boulder

Single-junction silicon cells dominate the terrestrial market due to their mature manufacturing base and costs that are highly competitive with even conventional carbon-based energy sources. However, it is expected that continued improvement in photovoltaic efficiency will be needed to ensure continued favorable economics, which may not be tractable via Si alone. III-V multijunction solar cells have demonstrated the highest power conversion efficiencies of any photovoltaic technology, with records of >47% under concentrated light and >39% under one-sun illumination, but at costs that are far from competitive for anything other than niche and/or critical applications, like (aero)space. Therefore, combining III-V and Si technologies into a single platform offers the promise of high efficiency at competitive costs. At the same time, the atmospheric rise of the organic-metal halide perovskites, with single-junction efficiencies of >25% (even with spectrum-mismatched bandgaps), and their high potential for low-cost production, including in the form of Si-based tandems, makes for a strongly compelling alternative.

This tutorial will give a brief general introduction to the field of multijunction solar cells for the use in terrestrial and space systems, including basic theoretical considerations of the benefits of using several junctions to convert the broad solar spectrum into electricity. We will then separate the remainder into two main Si-based hybrid tandem solar cell technology areas: III-V (with some consideration of other inorganic materials) and perovskite. Within, we will review the fundamentals of the materials systems themselves, including techniques used for producing them at photovoltaic qualities and the various unique complexities associated with the fabrication processes. Key issues related to efficiency- and reliability-limiting defects and properties will be highlighted, including recent develops toward their mitigation. The various different device architectures that have thus far been investigated within these tandem photovoltaic systems will also be reviewed, with an eye toward future progress.

Tyler Grassman is an assistant professor at The Ohio State University (Columbus, OH) in the Materials Science and Engineering and Electrical and Computer Engineering departments. His areas of interest and current research topics include III-V/Si tandem solar cell development, large-gap materials cells for space photovoltaics application, metamorphic materials for novel optoelectronics (including photovoltaics and infrared photodetectors), fundamental studies and engineering of extended defects in semiconductors, and electron microscopy/spectroscopy-based semiconductor materials characterization and methods development.

Mike McGehee is a Professor in the Chemical and Biological Engineering Department at the University of Colorado Boulder. He is the Associate Director of the Materials Science and Engineering Program and has a joint appointment at the National Renewable Energy Lab. He was a professor in the Materials Science and Engineering Department at Stanford University for 18 years and a Senior Fellow of the Precourt Institute for Energy. His current research interests are developing new materials for smart windows and solar cells. He has previously done research on polymer lasers, light-emitting diodes and transistors as well as transparent electrodes made from carbon nanotubes and silver nanowires. His group makes materials and devices, performs a wide variety of characterization techniques, models devices and assesses long-term stability. He received his undergraduate degree in physics from Princeton University and his PhD degree in Materials Science from the University of California at Santa Barbara.

TUTORIAL 8: Thin Film PV: CdTe, CIGS, and Other Polycrystalline Material and Device Technologies

Instructor: Mike Scarpulla, University of Utah, Salt Lake City, UT, USA
Billy J. Stanbery, Siva Power, Santa Clara, CA, USA

The promise of thin film photovoltaic technologies has always been to reduce material and production costs while providing high conversion efficiency to achieve competitive cost. More recently their low energy payback time has been recognized as a critical advantage in carbon reduction strategies reliant on TW-scale electrification. CdTe and Cu(In,Ga)Se2 (CIGS) (as well as perovskites, subject of another tutorial) have in the past decade demonstrated conversion efficiencies in the same >20% range as multicrystalline Si. The fact that these technologies can achieve such high performance is truly remarkable because they consist of heterogeneous stacks of polycrystalline material layers with grain boundaries and interfaces spaced only microns from each other. What special attributes enable such high performance from such structurally imperfect materials? What are the process requirements for their cost-effective production? This tutorial will introduce participants to the leading thin film technologies ranging from the commercially successful to those in research or development stages. We will examine their materials, processing methods, device structures, and how these come together. The outstanding challenges will be discussed for each technology and materials and device concepts on the horizon will be introduced

Mike Scarpulla has worked in thin film photovoltaics for over a decade and in compound semiconductors for 18 years. He holds a joint appointment as an Associate Professor in the departments of Materials Science and Engineering and Electrical and Computer Engineering at the University of Utah. He has served in organizing the PVSC in various roles including chairing Area 2 multiple times. His current photovoltaic research is in group-V doping and the Cl activation process in CdTe as well as electrical defect spectroscopies. He enjoys the nexus of defect physics, materials, crystal growth, processing, device physics, materials and device characterization, and product engineering offered by thin film photovoltaics. His specialties are crystal growth and processing, point defects, and structural and electrical characterization. He is an author on more than 95 peer-reviewed publications and many conference proceedings. Mike earned his Sc.B. from Brown University in 2000 and PhD from UC Berkeley in 2006, both in Materials Science and Engineering. He was a postdoctoral scholar at UC Santa Barbara from 2006-2008 when he joined the University of Utah. In his spare time he enjoys family, friends and colleagues, hiking, climbing, biking, and skiing.

Billy J. (BJ) Stanbery has worked in industry and academia on a host of PV technologies including Si, OPV, GaAs, and CIGS for over 40 years. He is both an entrepreneur and scientist, working to build bridges between laboratory research and commercialization. He is currently serving as Chief Science Officer of Siva Power, with his efforts focused on scaling of innovative tools and processes for high-volume, low-cost manufacturing of durable CIGS modules. He’s an ardent proponent of the need for an integrated computational materials engineering approach to accelerating industrial product development. Thus his work combines analysis of the device and defect physics of multinary compound semiconductor devices, thermochemistry of film growth and reactor modeling with statistical methods for optimization of processes and customization of rapid thermal co-deposition (RTC) and ALD production tools for CIGS module manufacturing. BJ earned B.S. degrees in both Mathematics and Physics from UT Austin, an M.S. in Physics from UW Seattle, and a Ph.D. in Chemical Engineering from UF Gainesville. He served as General Chair of the 38th IEEE PVSC in Austin and IEEE Vice-Chair of WCPEC-6 in Kyoto.

TUTORIAL 9: 100% renewable future

Instructors: Prof Andrew Blakers, Australian National University

This tutorial will explore strategies, costs and timelines for deep renewable electrification of energy services leading to rapid reductions in global greenhouse emission of three quarters at low cost. Solar photovoltaics (PV) and wind constitute about two thirds of global annual net new generation capacity additions. Balancing an electricity system with 50-100% variable PV and wind is straightforward using off-the-shelf techniques comprising strong interconnection over large areas (million km2) to smooth out local weather; storage; demand management; and occasional spillage of renewable electricity. We will explore the technology and costs of HVDC long-distance transmission; storage in the form of pumped hydro and batteries; and the interplay of storage, transmission and spillage. Reference will be made to Australia which is installing PV and wind 4-5 times faster per capita than the EU, USA, Japan or China. Emissions reductions of 50% can be achieved through conversion of electricity supply to PV & wind, coupled with conversion of land transport to renewable electricity (mostly via electric vehicles) and low temperature air & water heating & cooling to renewable electricity (mostly via heat pumps). This requires only off-the-shelf technology but requires an increase in global electricity production of 50%. Longer-term opportunities for emissions reductions will be explored including conversion of industrial heating to renewable electricity; and the use of PV and wind to create energy-rich metals, materials and synthetic fuels to eliminate emissions from industrial processes and aviation. Reading: https://ieeexplore.ieee.org/document/8836526

Andrew Blakers is Professor of Engineering at the Australian National University. He was a Humboldt Fellow and has held Australian Research Council QEII and Senior Research Fellowships. He founded the ANU solar photovoltaic group and laboratory. His research interests are in the areas of silicon photovoltaic solar cells and renewable energy systems. He was co-inventor of the PERC silicon solar cell technology, which currently has half of the global solar market and cumulative module sales of around $40 billion. He was co-inventor of Sliver solar cell technology, the subject of a $240 million commercialisation effort by Transform solar. He has interest in sustainable energy policy and is engaged in detailed analysis of energy systems with high (50-100%) penetration by wind and photovoltaics with support from pumped hydro energy storage.

TUTORIAL 10: Introduction to Photovoltaic Materials Characterization

Instructor: Dr. Harvey Guthrey , NREL
Dr John Moseley , NREL

The performance of photovoltaic devices is governed by the structural and chemical properties of the materials used as well as the interactions between the different materials that make up the devices. Understanding these properties requires the use of a variety of characterization techniques based on different probing methods designed to expose specific material properties. Electron beams are one type probe that allow researchers to probe the structure, chemistry, and electro-optical properties of photovoltaic materials from millimeter-scale down to the atomic-scale. In this tutorial we will provide a detailed survey of electron beam based characterization techniques used to study photovoltaic materials and devices from routine analyses through cutting edge methods. The discussion of each technique will focus on what information can be attained (as well as what cannot) and how that information can be related to photovoltaic parameters. One critical factor in the interpretation of electron beam based characterization data is understanding where the information corresponds to within the sample (e.g. surface, bulk, etc.…). Within a portion of this tutorial we will also provide an interactive session focused on modeling the interaction volume for scanning electron microscopy (SEM) and transmission electron microscopy (TEM) experiments using open access software available to all attendees. Following the technique discussion and interactive modeling session we will survey current material problems related to different photovoltaic materials (CdTe, CIGS, III-Vs, silicon, halide-perovskites) in the context of electron beam based characterization techniques.

Dr. Harvey Guthrey is currently a research scientist in the Microscopy and Imaging Group at the National Renewable Energy Laboratory in Golden, Colorado. He received his Bachelor of Science in Physics from the University of North Texas and his PhD in Materials Science from the Colorado School of Mines in 2013. His research is primarily focused on the application of electron microscopy-based characterization techniques to photovoltaic materials. The overarching theme of his research is to gain better understanding of how the structural and chemical properties of photovoltaic materials can be altered to achieve higher efficiency devices.

John Moseley is a research scientist in the Microscopy and Imaging Group at NREL with 9 years’ experience in solar cell materials characterization. John earned a Ph.D. in Materials Science from the Colorado School of Mines in 2016, advised by Dr. Richard Ahrenkiel. John began working at NREL in 2012 as an intern in the Science Undergraduate Laboratory Internship (SULI) program and later served in graduate student and postdoctoral roles. He has collaborated extensively with leading thin-film solar cell manufacturer First Solar. His current research is focused on novel methods of extracting solar cell parameters from scanning electron microscopy-based measurements