IEEE JOURNAL OF PHOTOVOLTAICS, VOL. 4, NO. 1, JANUARY 2014 525 Interlaboratory Study of Eddy-Current Measurement of Excess-Carrier Recombination Lifetime Adrienne L. Blum, James S. Swirhun, Ronald A. Sinton, Fei Yan, Stanislau Herasimenka, Thomas Roth, Kevin Lauer, Jonas Haunschild, Bianca Lim, Karsten Bothe, Ziv Hameiri, Bjoern Seipel, Rentian Xiong, Marwan Dhamrin, and John D. Murphy Abstract—Excess-carrier recombination lifetime is a key parameter in silicon solar cell design and production. With the vast international use and recent standardization (SEMI PV13) of eddy-current wafer and brick silicon lifetime test instruments, it is important to quantify the inter- and intralaboratory repeatability. This paper presents the results of an international interlaboratory study conducted with 24 participants to determine the precision of the SEMI PV13 eddy-current carrier lifetime measurement test method. Overall, the carrier recombination lifetime between- laboratory reproducibility was found to be within ±11% for the quasi-steady-state mode and ±8% for transient mode for wafer samples, and within ±4% for bulk samples. Index Terms—Charge carrier lifetime, eddy currents, photocon- ductivity, silicon. I. INTRODUCTION T HE quasi-steady-state photoconductance (QSSPC) and transient photoconductance decay (PCD) lifetime mea- surement methods have been used worldwide for decades for the characterization of silicon wafers, bricks, and ingots in the photovoltaic (PV) industry [1]–[3]. Carrier lifetime measure- Manuscript received July 12, 2013; revised September 3, 2013; accepted September 24, 2013. Date of publication October 17, 2013; date of current ver- sion December 16, 2013. A L. Blum, J. S. Swirhun, and R. A. Sinton are with the Sinton Instru- ments, Boulder, CO 80301 USA (e-mail: adrienne@sintoninstruments.com; james@sintoninstruments.com; ron@sintoninstruments.com). F. Yan is with Applied Material, Santa Clara, CA 95054 USA (e-mail: Fei_Yan@amat.com). S. Herasimenka is with the School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, AZ 85287 USA (e-mail: sherasim@asu.edu). T. Roth is with Bosch Solar Energy AG, Arnstadt 99310, Germany (e-mail: thomas.roth3@bosch.com). K. Lauer is with the CiS Forschungsinstitut f¨ ur Mikrosensorik und Photo- voltaik GmbH, Erfurt 99099, Germany (e-mail: klauer@cismst.de). J. Haunschild is with the Fraunhofer Institute for Solar Energy Systems, Freiburg 79110, Germany (e-mail: Jonas.Haunschild@ise.fraunhofer.de). B. Lim and K. Bothe are with the Institute for Solar Energy Research Hamelin, Emmerthal 31860, Germany (e-mail: bianca.lim@isfh.de; bothe@isfh.de). Z. Hameiri is with the Solar Energy Research Institute of Singapore, National University of Singapore, Singapore (e-mail: seris.zh@gmail.com). B. Seipel is with SolarWorld Industries America, Hillsboro, OR 97124 USA (e-mail: Bjoern.Seipel@solarWorld-USA.com). R. Xiong is with Suniva Inc., Norcross, GA 30092 USA (e-mail: rxiong@ suniva.com). M. Dhamrin is with the Tokyo University of Agriculture and Technology, Tokyo 183-0057, Japan (e-mail: dhamrin@hotmail.com). J. D. Murphy is with the University of Oxford, Oxford OX1 2JD, U.K. and also with the University of Warwick, Coventry CV4 7AL, U.K. (e-mail: john.d.murphy@warwick.ac.uk). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/JPHOTOV.2013.2284375 ment is used in research laboratories to understand, design, and optimize new process technologies. It is used in manufacturing for product qualification and is also used in-line for process control and improvement. There is an important correlation be- tween the carrier lifetime that is measured at the brick/ingot or wafer level and final solar cell performance [4], [5]. SEMI PV13 [6], an eddy-current excess-carrier recombina- tion lifetime standard, was published in 2011 to ensure that all the measurements of this type are conducted in the same manner. This standard describes the proper calibrations and analysis techniques for the measurement of excess-carrier re- combination lifetime in silicon wafers, ingots, and bricks using an eddy-current conductance sensor. To date, no large scale international investigation into the reproducibility of this mea- surement method has been completed. The purpose of such a round robin study is to determine the inter- and intralabora- tory reproducibility of the carrier recombination lifetime test method, to verify the test and analysis methods, and to indicate areas for improvement in the test method. The key components to carry out such a study are: 1) To select a proper sample set that is representative of the samples measured in both the PV industry as well as in PV research and development using the excess-carrier recombination lifetime measurement system. 2) To select laboratories to participate in the study with equipment that can be representative of the entire popula- tion of similar tools. For this study, wafer lifetime testers (WCT 120 from Sinton Instrument, Boulder, CO, USA) [1] and bulk lifetime testers (BCT 400 and BLS I from Sin- ton Instruments, Boulder, CO, USA) [7] were of particular interest. 3) To analyze the measurement data obtained from the par- ticipating test laboratories to determine the reproducibility of the measurement system and to determine the possible sources causing poor reproducibility, if any. Past work has addressed the uncertainty of the QSSPC and transient PCD measurements [8]; in 2011, a similar small- scale round robin study was carried out [9]. This study of both eddy-current and microwave PCD measurements concluded a 16–19% deviation for bulk samples and an 8–15% deviation for wafer samples. The round robin study involved both monocrys- talline and multicrystalline wafer and bulk samples. Addition- ally, a comparison of passivated wafer lifetime with bulk mea- surements on ingots was included in the past study. There are two main differences between the previous study and the study being presented here. First, the number of participating 2156-3381 © 2013 IEEE