PLENARY SPEAKERS

Area 1: Emily Warren, National Renewable Energy Laboratory, USA

Emily Warren is a staff scientist at the National Renewable Energy Laboratory where she works on high efficiency tandem solar cells, heteroepitaxy of III-Vs on Si, and the photoelectrochemical production of solar fuels. She received her PhD from the California Institute of Technology in 2013.

Title: Hybrid Tandem Solar Cells: Opportunities Beyond Two Terminals

Abstract: Tandem or multijunction solar cells offer the clearest path to high efficiency and high areal energy density photovoltaic energy conversion. Theoretically and at the laboratory scale, increasing the number of junctions is a simple way to create a record-setting device. There are multiple approaches to interconnecting the sub-cells in a tandem stack that have different trade-offs in terms of efficiency, cost, and manufacturability. Two terminal (2T) tandem solar cells have sub-cells that are optically and electrically connected in series, requiring that each sub-cell be current matched. Moving to three terminals (3T) or four terminals (4T) can eliminate requirements for current matching and polarity-changing interconnections (e.g., tunnel junctions), opening the possibilities for combining a broader range of absorber technologies.

3T tandems have attracted a great deal of interest at the laboratory scale for their high potential efficiencies. However, the coupled nature of 3T devices adds a degree of complexity to the devices themselves and the ways that their performance can be measured and reported. In this talk, I will discuss the recent progress in the field of 3T and 4T tandems, including our recently proposed taxonomy for naming 3T devices, experimental demonstrations, robust measurement approaches, and interconnecting 3T cells into strings.

Area 2: Christian Kaufmann, Helmholtz-Zentrum Berlin / PVcomB, Germany

Christian Kaufmann currently holds the position of principal scientist and group leader at the Competence Centre Photovoltaics Berlin (PVcomB), which is part of the Helmholtz-Zentrum Berlin für Materialien und Energie. His group’s research focuses on the application of coevaporated CIGSe compound semiconductor thin films in various device configurations, in particular superstrate devices and - lately - as bottom cells in monolithic CIGS/perovskite tandems..

Title: CIGS/Perovskite Thin Film Tandem Devices

Abstract: C.A. Kaufmann, T. Bertram, M. Jošt, A. Al-Ashouri, T. Kodalle, A. Ruiz Perona, J.A. Márquez Prieto, I. Kafedjiska, N. Maticiuc, R. Wenisch, H.A. Yetkin, G.A. Farias Basulto, P. Reyes Figueroa, T.J. Jacobsson, M.A. Ruiz Preciado, T. Unold, E. Unger, U.W. Paetzold, R. Klenk, I. Lauermann, S. Albrecht, R. Schlatmann

Chalcopyrite/perovskite tandem devices are among the current potentially low cost tandem photovoltaic (PV) technologies and hence fuel advances in chalcopyrite technologies to fulfill the requirements necessary to compete on the global PV market. They promise to combine high area power densities with large scale manufacturability. Exploiting the advantages of thin film technologies, they can be flexible and light weight and thus attractive for applications such as vehicle integrated PV and roofing.

Two-terminal tandem photovoltaic modules promise easy and cost-effective application in the field as they can simply substitute current modules in existing PV system environments. Four-terminal tandem devices may be developed sooner and offer an additional degree of freedom, as current matching requirements do not apply.

On rigid glass substrates, monolithic Cu(In,Ga)Se2/Cs0.05(MA0.23FA0.77)Pb1.1(I0.77Br0.23)3 tandem devices have demonstrated considerable technological advancement, reaching a photoconversion efficiency of 24.16%. This contribution will discuss technological challenges for thin film tandem technologies and report on recent advances.


Area 3: Ryan France, National Renewable Energy Laboratory, USA

Ryan France has been a scientist at NREL for 15 years, where he conducts research on both multijunction solar cells as well as novel subcell components for TPV, Space PV, and terrestrial use. He has helped develop many of the high efficiency inverted metamorphic multijunction solar cells at NREL, including several recent record efficiencies.

Title: Triple-Junction III-V Solar Cells with 39.5% AM1.5 and 34.2% AM0 Efficiencies

Abstract: III-V multijunction solar cells have the highest efficiencies of any PV technology. These devices are currently the dominant space PV technology and are being investigated for a wide range of other applications where efficiency is a key metric. In this presentation, we describe a 3-junction cell with the highest 1-sun efficiency to date: 39.5% under the global spectrum, which is higher than previous 6-junction devices. When tuned for the space spectrum, the cell achieves 34.2% beginning-of-life efficiency, without consideration for radiation hardness. These efficiency improvements are enabled by combining advances in device architectures and extended-defect control strategies. This latest 3-junction device includes a high-performance front-junction GaInP top cell, an optically thick strain-balanced quantum well middle cell, and a lattice-mismatched GaInAs bottom cell with record performance despite dislocations. These advances not only allow high efficiency photovoltaics for both space and terrestrial PV applications, but also help enable new applications of III-V materials.

Area 4: Eszter Voroshazi, Univ. Grenoble Alpes, CEA, Liten, INES, France, France

Eszter Voroshazi is head of the PV module process lab at CEA-INES (National Institute for Solar Energy) in France working on novel materials, module interconnection and packaging technologies for conventional and integrated PV modules from early concepts up to pilot-scale demonstration. She has previously worked at Imec and obtained her PhD title from KULeuven in Belgium in 2012.

Title: Sustainable Silicon PV Cell and Module Materials and Technologies

Abstract: Rémi Monna, Vincent Barth, Timea Bejat, Eeva Mofakhami, Nouha Gazbour, Wilfried Favre, Florent Pernoud, Johann Jourdan, Aude Derrier

The sustainable manufacturing imperative of the PV industry triggered by the exponential growth to TeraWatt scale annual production capacity is redefining technical roadmaps and the industrial landscape. Integrating eco-design in research considering lifecycle analysis, scarcity, toxicity and circularity is becoming essential. In this talk following an introduction of this novel framework for research, we will specifically focus on the role of Ag in metallization as 10% of global supply has already been directed to PV in 2020, hence material scarcity is one of the main concerns to tackle. To reach sustainable levels the research and industry community should strive towards the ambitious target of less than 5mg/Wp consumption by 2030 requiring at least a 10-fold reduction. Overview of innovations in cell metallization and interconnection technologies reducing scarce material consumption while meeting the requirements of low-temperature and low-stress processing imposed by the new generation of Si cells technologies and decreasing wafer thickness will be presented. An additional critical lever to meet this goal is the increase of module performance offered by the latest generation passivated contact single junction devices reaching up to 25% efficiency on industrial scale devices, and silicon-perovskite tandem devices with a performance of nearing 30% on small area. Finally yet importantly, module packaging materials integrating thermoplastic encapsulants, bio-sourced materials will be discussed as enablers for both light-weight modules for ease of integration and high-value recycling.


Area 5: Mariana Bertoni, Arizona State University, USA

Mariana Bertoni is the Fulton Energy and Materials Professor in the School of Electrical, Computer and Energy Engineering at Arizona State University. She joined ASU’s faculty after holding senior scientist positions at two startup companies in the photovoltaic industry and a postdoctoral fellowship at the Massachusetts Institute of Technology. Professor Bertoni received her Ph.D. from Northwestern University in Materials Science and Engineering in 2007 and her Diploma in Chemical Engineering from the Instituto Tecnológico de Buenos Aires. She is a former Fulbright Scholar and a Marie Curie Fellow. In 2022, she was named Hopkins Professor and in 2018, she won the National Academy of Engineering Grainger Foundation Frontiers of Engineering Award for Advancement of Interdisciplinary Research. Her research aims to understand how intrinsic and extrinsic defects affect the electrical and optical properties of energy materials and accordingly engineer the processing steps that will maximize performance.

Title: Operando Science: the Emerging Role of X-ray Imaging and Spectroscopy

Abstract: The last decade has witnessed a rapid growth in the use of in situ and operando techniques, in which materials and devices are probed under conditions which resemble as closely as possible those used under real operating environments, with time-resolved measurements increasingly being made as well. Electron beam techniques and Kelvin probe force microscopy have led the way as powerful tools to study charge separation and recombination at the nanoscale. However, despite their strengths, there are several limitations imposed by their penetration depth, and sample preparation requirements that limit their ability to suitably represent the full system under study.

In this plenary I will cover how the high penetration of hard X-rays is ideal to noninvasively obtain information from full devices demanding little or no specimen preparation even under working conditions. Workhorse techniques such as X-ray diffraction (XRD), X-ray fluorescence (XRF), and multi-dimensional imaging can be coupled with X-ray beam–induced current (XBIC) to study the effect of structure and composition on the spatial variations of charge separation inside a device. Furthermore, because the interaction of X-rays with matter is highly energy-dependent around the absorption edges of the probed atoms, energy-dependent X-ray studies can be used to probe changes in the local atomic environments during operation with high sensitivity.

The field of operando science is growing rapidly and offers tremendous opportunities to uncover the relationship between structure, properties, composition and performance at the nanoscale for PV materials and devices.


Area 6: Jinsong Huang, University of North Carolina-Chapel Hill, USA

Jinsong Huang is currently Louis D. Rubin, Jr. Distinguished Professor at University of North Carolina at Chapel Hill. He has been working on organic semiconductors and hybrid perovskite semiconductors for applications in solar cells, photodetectors, X-ray detectors and light emitting diodes in the last 22 years. His current research interests include solution processed electronic materials for applications in energy, sensing, and consumer electronics

Title: Defects in Metal Halide Perovskites

Abstract: Electronic defects in semiconductor materials play critical roles in determining the efficiency and stability of their photovoltaic devices. Eliminating deleterious defects in semiconductors or passivating them during the fabrication process of solar cells has become one of the most popular approaches for solar cell fabrication and upscaling. This scenario also prevails for metal halide perovskite solar cell, with a rapid increase of the power conversion efficiency of small area perovskite solar cells from 3.8% to 25.7% due to defect passivation which also enhances the stability of perovskite solar cells.

Defects in perovskites have been intensively studied in recent years, but there is no consensus on the defect chemical nature, their distributions, and their evolution during degradation. I will present the general types of defects in polycrystalline perovskites made from solution process. I will report on our demonstration of using the drive-level capacitance profiling (DLCP) technique for spatial and energetic distributions of charge traps. By combining the DLCP technique with electrical poling, we can determine the charge states and the chemical nature of mobile defects in perovskites. This revealed some astonishing discovery on the defects in perovskites of different compositions, and mechanism of solar cell degradation under reverse bias & illumination.


Area 7: Jenya Meydbray, PV Evolution Labs (PVEL), USA

Jenya Meydbray is CEO and co-founder of PVEL, an independent performance and reliability laboratory that evaluates PV and energy storage equipment. He has over fifteen years of experience supporting asset owners, investors and equipment buyers with data and services that mitigate technology risk in solar procurement and optimize the performance of operating assets.

Title: PV Performance and Reliability Over Time: The Impact of New Materials and Technologies

Abstract:PV cell technology and module design are in a period of dramatic transformation. The supplier base for raw materials continues to diversify. Advanced PV cell architectures and module designs are being deployed at a rapid pace. But no one knows for certain if recent, celebrated technical advances can fulfill the fundamental purpose of most product improvements: reducing the installed cost per kilowatt-hour of solar energy over time, thereby enabling the deployment of more solar assets. Demonstrable proof will only become available after 25+ years of field operation.

When long-term field data from operating assets is absent, lab testing is the next best source of empirical performance and reliability data. This session will compare recent and historic independent test results for different PV module designs, cell architectures and raw materials. It will highlight the most promising technical advances as well as examples of unexpected degradation modes that surfaced in testing but were poorly understood at the time new products were introduced. Examples from the recent past point to an urgent and growing need for collaborative research on test design and more transparent data sharing. It is the engineers and researchers at the forefront of solar PV technology who can prevent failures before they reach the field.


Area 8: William J. Gambogi, DuPont, USA

William Gambogi is an applied physicist and a Research Fellow with DuPont. Bill retired in 2021 after a 45-year career in R&D. He has published extensively over the past 12 years on PV material and module durability and test methodology development.

Title: Progress in PV Material Durability Test Methodologies

Abstract: Accelerated test methods to assess the durability of photovoltaic modules is a crucial area of research in the PV technical community. The seminal work in this area was conducted under a US DOE program in the 1980s led by researchers at the Jet Propulsion Laboratory. Many of the industrial standards for testing PV module reliability were based on this work. As the installed PV base has grown exponentially, new materials and module designs have been introduced into the industry at an accelerated pace at the same time as price pressures have pushed for lower cost materials and designs. These cost pressures led to some notable early product field failures that were not caught by existing test standards. We will present results obtained with global PV reliability research groups on advanced targeted module and materials accelerated testing. Using field experience and assessment, we will present insights into failure mechanisms and comparison to accelerated testing results. In this talk, we will review the recent progress and direction in accelerated testing of PV materials and modules.

Area 9: Babak Enayati, National Grid, USA

Babak is the Manager of the New Technology team at National Grid, which is responsible for the implementation of the new technologies to meet National Grid’s Intelligent Electric Network objective to deliver clean and affordable energy to its customers. Babak is currently serving as the Vice Chair of IEEE 1547 and P2800 standards. He has over 17 years of industry experience on the integration of clean energy resources to the electric power system.

Title: PV Grid Integration Challenges and the Need for Grid Enhancing Technologies

Abstract: With the increasing penetration of photovoltaic energy resources integration to the electric grid, system operations is becoming more challenging. This session will highlight a series of challenges associated with the PV integration to the electric grid. The session will also feature technologies that could maximize the utilization of the existing electric grid capacity as a near-term complement to planning for and building new transmission and distribution grid. Utilization of these grid enhancing technologies could play a key role in achieving the clean energy targets. The presenter will describe commercially available grid enhancing technologies that can dramatically defer distribution and transmission capital investment while maximizing the utilization of the existing capacity of the electric grid.

Area 10: Dazhi Yang, Harbin Institute of Technology, China
Area 10 Presenter: Jan Kleissl, Johns Hopkins University, USA

Dazhi Yang received his PhD from the National University of Singapore in Electrical Engineering. He is now a Professor at the Harbin Institute of Technology.

Jan Kleissl received his PhD from the Johns Hopkins University in Environmental Fluid Mechanics. He is now the Director of the Center for Energy Research and the principal investigator of the DERConnect testbed at UC San Diego.

Title: Solar Forecasting: Its Dependence on Atmospheric Sciences and Implications for Grid Integration

Abstract: The ability to forecast solar irradiance plays an indispensable role in solar power forecasting, which constitutes an essential step in planning and operating power systems under high penetration of solar power generation. Since solar radiation is an atmospheric process, solar irradiance forecasting, and thus solar power forecasting, can benefit from the participation of atmospheric scientists. In this talk, the two fields, namely, atmospheric science and power system engineering are jointly discussed with respect to how solar forecasting plays a part. Firstly, the state of affairs in solar forecasting is elaborated; some common misconceptions are clarified; and salient features of solar irradiance are explained. Next, five technical aspects of solar forecasting: (1) base forecasting methods, (2) post-processing, (3) irradiance-to-power conversion, (4) verification, and (5) grid-side implications, are reviewed. Following that, ten research topics moving into the future are enumerated; they are related to (1) data and tools, (2) numerical weather prediction, (3) forecast downscaling, (4) large eddy simulation, (5) dimming and brightening, (6) aerosols, (7) spatial forecast verification, (8) multivariate probabilistic forecast verification, (9) predictability, and (10) extreme weather events. Last but not least, a pathway towards ultra-high PV penetration is laid out, based on a recently proposed concept of firm generation and forecasting.

Area 11: Annick Anctil, Michigan State University, USA

Dr. Annick Anctil is an associate professor in Civil and Environmental Engineering at Michigan State University, where she leads research on Sustainable Energy Systems. The core of her research is evaluating the environmental impact of photovoltaics technologies.

Title: How Anticipatory Sustainability Assessment Can Help PV Deployment

Abstract: RAs PV becomes a major source of electricity production, new questions emerge about the environmental impact of manufacturing solar modules, the toxicity of the modules, the impact on land and ecosystems during and after system installation, and finally, modules recyclability at end-of-life. Concerns from the public and opposition groups can also create significant delays and costs in project deployments due to the lack of studies on the environmental benefit, toxicity, or end-of-life management of PV. Anticipatory sustainability assessment can evaluate the potential environmental impact of current and future technologies. Results are helpful to address misconceptions about solar impacts and guide greener PV module design, construction, and recycling. Examples of recent projects on transparent photovoltaics for BIPV, tellurium scarcity, modules toxicity, and solar co-location with agriculture will be presented.