23 Oct 2012   |   9:00 am – 2:00 pm,   Sands Expo and Convention Centre, Level 3, Angsana Room 3E Marina Bay Sands, 10 Bayfront Avenue, Singapore 018956

Symposium on Accurate Measurements of PV Cells and Modules (A Satellite Event of PV Asia Pacific Conference 2012)



Characterisation and performance testing are critical to the development of existing and emerging photovoltaic technologies and the growth of the solar industry. As new solar products are being developed and manufactured, the energy conversion efficiency and other critical parameters must be accurately measured and tested against globally recognised metrological standards. Products based on new technologies also call for advanced techniques, standards and measurement methodology.

This symposium, organised and hosted by the National Metrology Centre (NMC), a member of the Agency for Science, Technology and Research (A*STAR) of Singapore, will provide a rare platform focusing on measurement issues of PV devices and is ideal for metrology experts, research scientists, test engineers and graduate students working in this field to share their work and exchange ideas.

The symposium will feature internationally recognised experts who will share their expertise on accurate measurements of PV cells and modules. Local PV metrology and testing labs will also present their latest developments on state-of-the-art PV measurements facilities and capabilities. The symposium will consist of invited and contributed papers for oral or poster presentation.

Who should attend

Metrology experts, researchers, scientists, engineers, manufacturers, students, and users of PV products, from research institutes, universities, and industry, as well as anyone interested in the latest industry trends, challenges, and R&D in PV measurements.





Welcome & Introduction
Dr Liew Yun Fook Thomas, Acting Executive Director of National Metrology Centre (NMC), A*STAR, Singapore


Overview New Developments in the Field of Primary Calibration of Reference Solar Cells with the DSR Method
Dr Stefan Winter, Head of Working Group 4.14 Solar Cells, PTB, Germany.

Abstract: The Differential Spectral Responsivity (DSR) method allows the determination of the absolute spectral responsivity and nonlinearity of solar cells with the lowest uncertainties. The method is explained and a newly designed multi-functional flexible facility for the primary calibration of reference solar cells and the spectral characterization of all solar cell types, developed and built at PTB, is shown. By using a tunable laser system, the new setup avoids the main problem of monochromator-based systems: the low optical power level of the monochromatic beam. Thus it enables a significant reduction of the uncertainty for the short circuit current under standard test conditions ISTC of large solar cells.


PV Cell and Module Calibrations at NREL
Dr Keith Emery, National Renewable Energy Lab (NREL), USA

Abstract: We discuss procedures for determining the photovoltaic (PV) efficiency with respect to standard reference conditions—from 1-sun to low concentration to high concentration. For the NREL PV Performance Characterization team, our scope is any PV cell or module technology of any size, voltage, or current. NREL’s primary reference cell calibration procedures based on natural sunlight rely on determining the spectrally and intensity-corrected short-circuit current. We measure the 5-degree field of view direct-beam irradiance using a primary absolute cavity radiometer, and we use a silicon-based spectral radiometer to measure the spectrum from 300 to 1100 nm. We use a comprehensive atmospheric transmittance model to extend the measured spectrum to 300 to 4000 nm. This primary calibration method has been followed at NREL since 1984. NREL uses solar simulators and natural sunlight for the secondary calibration of cells and modules.  Spectrally adjustable 1-sun and concentrator simulators are used for multijunction cells to minimize the increased measurement error as the number of junctions is increased. We discuss the challenges and dominant error sources in evaluating state-of-the-art and commercial cells and modules at NREL.


Element Technologies for Accurate Measurements of PV Devices
Dr Yoshihiro Hishikawa, Leader of Research Center for Photovoltaics (RCPV), AIST, Japan

Abstract: Recent development of various PV devices and growth of PV industry have put more significance on the accurate performance measurements of PV devices and calibration of PV reference devices than ever before. Development of new PV devices usually also demands novel measurement technologies. For example, high-efficiency heterojunction crystalline silicon (c-Si) solar cells require more attention on their temporal response for the current-voltage curve measurement, due to the capacitance effect. Also, recent thinner busbar electrode and thinner wafer configurations etc. have necessitated explicit consideration on the distribution of the electric potential within the surface of the c-Si solar cells. Novel materials and structures such as dye-sensitized solar cells and organic solar cells, have also posed careful re-investigation of the conventional measurement technologies, due to their very slow temporal responses and wide variation of spectral responses, respectively. Technologies for the PV energy rating, or the kWh performance measurement, include characterization of the power (kW) rating under different climate conditions such as irradiance, temperature and spectrum. They are becoming increasingly important as the basis of evaluating the value of various PV devices under the outdoor operating conditions. The present status and future prospect of those technologies are discussed based on updated experimental results.


Tea Break


Latest Development of Solar Radiometry at National Metrology Centre of Singapore
Dr Xu Gan, Principal Metrologist of National Metrology Centre (NMC), A*STAR, Singapore

Abstract: To meet the demands for traceable and accurate calibration from solar energy industry, NMC had initiated and completed a three year project aimed at development of solar radiometry primary standards and facilities for the measurement, characterisation and calibration of solar PV cells. Through the project, we have successfully developed a number of key facilities for the measurement of spectral and electrical properties of solar PV cells: a) A multi-functional differential spectral responsivity (DSR) measuring system for relative and absolute DSR in the spectral range of 280 nm to 1200 nm under bias light irradiance and its linearity, spatial uniformity and temperature coefficient. The system is able to perform primary calibration of reference solar cells with direct traceability to NMC's spectral responsivity scale established through a laser based cryogenic radiometer. The expanded uncertainties (k=2) for absolute spectral responsivity at 650 nm and short- circuit current under standard test conditions are evaluated to be 0.6% and 0.8% respectively; b) an automatic I-V tester using a super class solar simulator for full I-V characterisation of single PV cell up to 156 mm x 156 mm. With a built-in spectroradiometer and motorised sample stage, the spectral mismatch and spatial corrections can be automatically calculated. High-speed synchronisation of monitor signal and PV cell signal allows real time automatic correction to the irradiance generated by the solar simulator; c) A facility for QE-IPCE and surface reflectance measurements of small, none-regular shaped solar PV cells using micro probe bars; d) A spectral irradiance measuring facility for both CW and pulsed solar simulators. With these facilities, NMC is able to provide a one-stop measurement service for our customers. The design features and performance of these devices including uncertainty evaluation will be described in details in this paper.


Advanced Characterisation of Silicon Wafer Solar Cells
Dr Bram HOEX, Cluster director and head of PV characterisation at the Solar Energy Research Institute of Singapore (SERIS)

Abstract: Advanced characterisation plays an important role for further improvements of the cost effectiveness ($/Wp) of all types of solar cells. This contribution presents an overview of advanced characterisation techniques that are presently being used for the analysis of silicon wafer solar cells, either in the laboratory or in the factories. In this presentation we will mainly focus on the information that can be obtained from a finished silicon wafer solar cell. It will be shown that the various loss mechanisms for the current at the maximum power point can fully be quantified by a combination of high-precision measurements. A similar quantitative study will be presented for recombination losses and fill factor losses at the maximum power point. This extensive quantitative analysis, which is not limited to silicon wafer solar cells, provides solar cell researchers the information required to further optimize the performance of their solar cells.


Photovoltaic Capabilities in Institute of Materials Research & Engineering, A*Star, Singapore
Dr. Zhang Jie, Program Manager of Institute of Materials Research & Engineering (IMRE), A*STAR, Singapore

Abstract: Next generation photovoltaic technologies, such as polymer/organic PV (OPV), Dye-sensitised solar cell (DSC), and inorganic thin film solar cell, offer promise for the realization of a low cost, printable, portable, and flexible renewable energy source. The power conversion efficiencies of these new generation PV technologies have been improving steadily, the fundamentals of processes and device physics are being researched extensively. In this presentation, the PV research and development in IMRE, A*STAR will be showcased. IMRE’s expertise in PV materials design and synthesis, device fabrication, device physics and degradation mechanism, and the state-of-art optoelectronics characterization capabilities can be used to address industry PV product development needs through consultancy, testing services and/or joint R&D project.


Testing the Next Generation PV Modules Requires Longer Illumination
Ir. Stefan Roest, Technical Director of Eternal Sun B.V., The Netherlands

Abstract:Testing the latest generation PV modules requires longer illumination than current practice. Conventional flash testers generate 10 - 50 ms light pulses. For scientifically sound Measurements, a light pulse upwards of 1 second is required. Three PV module technology trends requiring longer illumination are: 1. Highly capacitive c-Si and thin-film modules, 2. Modules involving chemical reactions (OPV) and 3. Module integrated electronics. These module technologies all exhibit long response times. Measuring capacitive modules with a 50 ms light pulse leads to errors in output power of ± (3 - 5) %, depending on IV sweep direction. In OPV modules, the charge transport to the electrodes can take hundreds of milliseconds. Micro inverters and power point trackers need seconds to achieve steady state output conditions. Longer illumination causes heating of the solar modules, resulting in lower output power. At 1 sun illumination the temperature increase is approximately 0.2 - 0.6 ° C/s. This effect can be neglected or compensated for.



About the Speakers

Dr. Stefan Winter is a physicist at the Photometry and Applied Optics Department, Optics Division, Physikalisch-Technische Bundesanstalt (PTB), the national metrological institute in Germany. He works since 1996 in the field of radiometry and photometry. His research covers areas like the development of an easy to use integrating sphere scanner with E27 socket that suits industrial needs, new methods for the determination of the uncertainty and correlation of spectrally resolved measurements with the Monte Carlo method, a laser-based realization of the spectral irradiance without black body, and the calibration of detectors using tunable lasers. Since 2009 he is the head of the Working Group “Solar Cells”.

Dr. Keith Emery established and has managed the Cell and Module Performance Characterization team at NREL since 1980. The team established the procedures for calibrating cells and modules that have since been codified in standards and adopted by the international PV community. He received his B.S. physics and M.S.E.E. from Michigan State in 1979 and worked on a PhD at Colorado State in 1979-1980 and 1982. His graduate thesis work was in the area of comprehensive modeling of the pulsed HF laser, electron and laser beam vapor phase epitaxy of oxides and nitrides, and ion beam sputtering of tin oxide on Si. He has 308 publications and 5 chapters in PV books to date. His ISO 17025 PV accredited calibration group provides the community with reference cell calibrations and efficiency certification. He is also active in PV standards development and consulting on PV performance rating hardware, solar simulation, current versus voltage measurement software and procedures. He is a life time member of the Colorado Renewable Energy Society (CRES), senior member of IEEE, member of the ASTM E44 and IEC TC-82 PV standards committees. He is an associate editor in IEEE Journal of PV and on the editorial board of Progress in Photovoltaics and Renewable Energy. He is co-awardee of two R&D 100 awards, and recipient of the 2007 Paul Rappaport, 2009 Harold M. Hubbard award, and the 2012 World Renewable Energy Network Pioneer Award. Further details of the team’s activities can be found at

Dr. Yoshihiro HISHIKAWA is a senior research scientist at the Research Center of Photovoltaic Technology, National Institute of Advanced Industrial Science and Technology (AIST) in Japan. His carrier in PV research started in 1982 in the area of basic research and characterization of amorphous silicon solar cells at Sanyo Electric. Since he moved to AIST in 2003, he has been engaged in the development of accurate performance characterization technologies for novel photovoltaic devices. He is the leader of the Calibration, Standards and Measurement Team at AIST, which is responsible for the research on accurate performance characterization and energy rating of all kinds of photovoltaic cells and modules as well as calibration of reference cells.

Dr Xu Gan received his M.Sc. and Ph.D. degrees in laser physics from University of Manchester in 1981 and 1983 respectively and worked as a senior research scientist, lecturer and associate professor in a number of universities in UK and China between 1984 and 1991 before joining the National Metrology Centre (NMC), A*STAR Singapore in 1991 of where he is currently a principal metrologist. In the past twenty years, he has been instrumental for the development & establishment of Singapore’s national measurement standards and facilities in optical radiation metrology. He is the principal investigator for the project “Development of Solar Radiometry Primary Standards and Facilities for Solar PV Cell Characterisation and Calibration” sponsored by A*STAR since 2009. Dr Xu is an internationally recognised expert in optical radiation metrology. He was the chairman of the Technical Committee on Photometry and Radiometry of the Asia Pacific Metrology Programme from 2003 to 2006 and the Singapore representative to the Consultative Committee on Photometry and Radiometry of the International Commission on Weights and Measures since 1999. He has published over 30 papers and presented at numerous international conferences & seminars.

Dr Bram HOEX is a Director and Group Leader at the Solar Energy Research Institute of Singapore (SERIS) and project manager of various (semi) industrial silicon wafer solar cell projects in the silicon photovoltaics cluster at SERIS. He has extensive experience in the area of processing and advanced characterisation of high-efficiency silicon wafer solar cells. In 2008 he won the SolarWorld Junior Einstein Award and the Leverhulme Technology Transfer Award for his work in the area of high-efficiency silicon wafer solar cells.

Dr. Zhang Jie is a Senior Scientist and Program Manager of the Institute of Material Research and Engineering at A*STAR in Singapore.  She manages PV, Printed Electronics, and Advanced Energy Storage programs to develop advance material system, device fabrication and characterization, and prototype capabilities. Previously at Motorola, she was Principal Staff Engineer and managed core technology group for the large area electronics technology and commercialization.  She also has extended experience in advanced microelectronics package process and reliability evaluation for wireless communication devices. Dr. Zhang co-chaired the 1st and 2nd iNEMI Printed and Organic Electronics and participated in international working groups that developed IEEE standards for large area flexible electronics and nanotechnologies.  She has received 18 US patents. She is actively organizing printed electronics conferences and workshops, and frequently been invited to present at international conferences. She has co-edited the first book of printed organic and molecular electronics and co-authored three book chapters in organic and nano materials, processes and applications.

Who should attend

Metrology experts, researchers, scientists, engineers, manufacturers, students, and users of PV products, from research institutes, universities, and industry, as well as anyone interested in the latest industry trends, challenges, and R&D in PV measurements.