Photo of Sarah Kurtz.

Sarah Kurtz

Contingent Worker-Emeritus Researcher


Dr. Kurtz is a Research Fellow with the National Center for Photovoltaics (NCPV). She is a professor at the University of California Merced. As a research fellow, she will also contribute to select NREL projects.

Dr. Kurtz is a world-renowned expert in the fields of multijunction photovoltaics (PV), concentrator PV, and PV reliability.

Kurtz and NREL colleague Jerry Olson championed the early use of multi-junction solar cells by showing that a top cell of gallium indium phosphide (GaInP) and a bottom cell of gallium arsenide (GaAs) can capture and convert photons more efficiently into electricity than previous attempts at using other materials. This breakthrough was embraced by NASA, which uses multi-junction solar cells based on this invention to power many space satellites, as well as the Mars rovers, Spirit and Opportunity.

Areas of Expertise

  • Cofounded PVQAT (International PV Quality Assurance Task Force) with the goal of creating international standards that will be the foundation of the next stage of growth for the PV industry.
  • Participated in the demonstration of the GaInP/GaAs solar cell invented by Jerry Olson, and published extensively on materials, devices, and implementation issues associated with this technology.
  • Implemented the first record-setting 3-junction (GaInP/GaAs/GaInAs) inverted metamorphic cell, invented by Mark Wanlass. This device structure, with the potential of reaching 45% efficiency, is considered to be one of the most likely successors of today's commercial multijunction cells.
  • Studied dilute nitride cells, helping to establish that MOVPE is unlikely to be a successful growth technique for GaInAsN solar cells, paving the pathway for more success using MBE.
  • Supported the growing CPV industry by documenting the industry's progress, identifying issues that are important to the industry, and identifying ways to address these.
  • Participated in standards development, especially for power rating, and development of reliability tests for CPV modules.
  • Studied the effect of stress on amorphous silicon as a post-doc with NREL's Amorphous Silicon Team, 1985-1986.


B.A. Chemistry and Physics, 1979, Manchester College
Ph.D. Chemical Physics, 1985, Harvard University

Associations and Accreditations/Memberships

  • Member, IEEE and IEEE standards association
  • Member, American Solar Energy Society
  • Member, ANSI (participation in IEC standards writing)
  • Member, American Chemical Society

Professional Experience

Since Dr. Kurtz joined NREL1985 as a post-doc, her contributions to PV research at NREL have been more than significant. Throughout her tenure, Dr. Kurtz has played a critical role in developing and maintaining the lab's reputation in photovoltaic research and development, helping to illuminate how to grow high-quality cells, how to measure multi-junction cells, and how their performance is affected under various spectra. More recently, she has looked at reliability issues of PV modules integrated into larger systems.

In addition to her research, Dr. Kurtz serves as a mentor for students and post-doctoral fellows. From 2008 to 2017, she was group manager for the Reliability and Systems Engineering group at the NCPV. While having moved to California to work at the University of California Merced, she continues to support NREL through participation in PVQAT (the International PV Quality Assurance Task Force) and IEC in the development of international standards. Dr. Kurtz has helped to position NREL to be a lead in this critical area. She holds six patents and authored or co-authored over 100 refereed publications and over 100 conference proceedings.

Featured Publications

PV Module Reliability and Performance

  • Kurtz, S.; Wohlgemuth, J.; Sample, T.; Yamamichi, M.; Kondo, M.; Kelly, G. "Three-Prong Path to Comprehensive Technical Standards for Photovoltaic Reliability" Presented at 40th IEEE PVSC. Denver, CO, June 2014.
  • Kurtz, S. R.; Muller, M.; Jordan, D.; Ghosal, K.; Fisher, B.; Verlinden, P.; Hashimoto, J.; Riley, D. (2014). "Key Parameters in Determining Energy Generated by CPV Modules," Progress in PV. DOI:10.1002/pip.2544.
  • Kurtz, S. R.; Krishnani, P.; Freeman, J.; Flottemesch, R.; Riley, E.; Dierauf, T.; Ngan, L.; Jordan, D.; Kimber, A. "PV System Energy Test." Presented at 40th IEEE PVSC. Denver, CO, June 2014.
  • Jordan, D.C. and Kurtz S.R. (2014). "Photovoltaic Degradation Rates An Analytical Review" Prog. In PV, 2011 DOI: 10.1002/pip.1182.
  • Wohlgemuth, J.; Kurtz, S. "Photovoltaic Module Qualification Plus Testing" Presented at 40th IEEE PVSC, Denver, CO, June 2014.
  • Wohlgemuth, J.; Kurtz, S.; Sample, T.; Kondo, M.; Yamamichi, M. "Development of Comparative Tests of PV Modules by the International PV QA Task Force." Presented at 40th IEEE PVSC. Denver, CO, June 2014.
  • Jordan, D.C. and Kurtz, S.R. "Reliability and Geographic Trends of 50,000 Photovoltaic Systems in the USA." Presented at European PVSEC. 2014.
  • Jordan, D.C. and Kurtz, S.R. "Field Performance of 1.7 Gigawatts of Photovoltaic Systems." (2014). Journal of PV. Presented at 40th IEEE PVSC, Denver, CO, June 2014.
  • Eguchi, Y.; Ramu, G.; Lokanath, S.; Yamamichi, M.; Kurtz, S.; Wohlgemuth, J.; Yamada, E.; Kondo, M. "Requirements for Quality Management System for PV Module Manufacturing." Presented at 40th IEEE PVSC, Denver, CO, June 2014.
  • Kurtz S.; Whitfield, K.; Miller, D.; Joyce, J.; Wohlgemuth, J.; Kempe, M,; Dhere, N.; Bosco, N.; Zgonena, T. "Evaluation of High-Temperature Exposure of Rack-Mounted Photovoltaic Modules." Presented at 34th IEEE Photovoltaic Specialists Conference. Philadelphia, 2009 (IEEE).
  • Bosco, N.; Sweet, C.; Kurtz, S. "Reliability Testing the Die-Attach of CPV Cell Assemblies." Presented at 34th IEEE Photovoltaic Specialists Conference. Philadelphia, 2009 (IEEE).
  • Miller, D.M.; Kempe, M.D.; Kennedy, C.E.; Kurtz, S.R. "Analysis of Transmitted Optical Spectrum Enabling Accelerated Testing of CPV Designs." Proc. SPIE Optics and Photonics. San Diego, 2009.
  • Kntges, M,; Kurtz, S.; Packard, C.; Jahn, U.; Berger, K.; Kato, K.; Friesen, T.; Liu, H.; Van Iseghem, M. "Review on Failures of Photovoltaic Modules." (2013). Report IEA-PVPS T13-01.
  • Bosco, N. and Kurtz, S. "Quantifying the Thermal Fatigue of CPV Modules." Presented at CPV6. Freiburg, Germany, April, 2010.
  • Jordan, D. C. and Kurtz, S. R. "Analytical Improvements in PV Degradation Rate Determination." Presented at Proc. 35th PVSC. June, 2010.
  • Kurtz, S.; Muller, M.; Marion, B.; Emery, K.; McConnell, R.; Surendran, S.; Kimber, A. "Considerations for How to Rate CPV." Presented at CPV6. Freiburg, Germany, April, 2010.
  • Muller, M.; Marion, B.; Kurtz, S.; Rodriguez, J. "An Investigation into Spectral Parameters as they Impact CPV Module Performance." Presented at CPV6. Freiburg, Germany, April, 2010.
  • Pulver, S.; Cormode, D.; Cronin, A.; Jordan, D.; Kurtz, S.; and Smith, R. "Measuring Degradation Rates without Irradiance Data." Presented at Proc. 35th PVSC. June, 2010.

III-V Photovoltaic Devices and Their Application

  • Steiner, M.A.; Geisz, J.F.; Garcia, I.; Friedman, D.J.; Duda, A.; Kurtz, S.R. (2013). "Optical enhancement of Voc in high quality GaAs solar cells." J. Appl. Phys (113); pp. 123109-1 - 123109-11, 2013.
  • Geisz, J.F.; Steiner, M.A.; Garca, I.; Kurtz, S.R.; Friedman, D.J. (2013). "Enhanced external radiative efficiency for 20.8% efficient single-junction GaInP solar cells." Appl. Phys. Lett. (103); p. 041118.
  • Miller, O.D.; Yablonovitch, E.; Kurtz, S.R. (2012). Strong Internal and External Luminescence as Solar Cells Approach the ShockleyQueisser Limit. IEEE Journal of Photovoltaics (2:3).
  • Kurtz, S.; Myers, D.; McMahon, W.E.; Geisz, J.; Steiner, M. (2008). "A comparison of theoretical efficiencies of multi-junction concentrator solar cells." Progress in Photovoltaics: Research and Applications (16); pp. 537-546.
  • Kurtz, S.; Johnston, S.; Branz, H.M.; (2005). "Capacitance-spectroscopy identification of a key defect in N-degraded GaInNAs solar cells." Appl. Phys. Lett (86); p. 113506.
  • Kurtz, S.; Geisz, J.F.; Friedman, D.J.; Metzger, W.K.; King, R.R.; Karam, N.H. (2004). "Annealing-induced-type conversion of GaInNAs," J. Appl. Phys (95); pp. 2505-2508.
  • Kurtz, S.; Geisz, J.F.; Keyes, B.M.; Metzger, W.K.; Friedman, D.J.; Olson, J.M.; Ptak, A.J.; King, R.R.; Karam, N.H. "Effect of growth rate and gallium source on GaAsN." (2003). Appl. Phys. Lett. (82); pp. 2634-2636.
  • Kurtz, S.R.; Webb, J.; Gedvilas, L.; Friedman, D.J.; Geisz, J.F.; Olson, J.M.; King, R.; Joslin, D.; Karam, N. "Structural changes during annealing of GaInAsN." (2001). Appl. Phys. Lett. (78) pp. 748-750.
  • Kurtz, S.R.; Myers, D.; Townsend, T.; Whitaker, C.; Maish, A.; Hulstrom, R.; Emery, K. "Outdoor rating conditions for photovoltaic modules and systems." (2000). Solar Energy Materials and Solar Cells (62); pp. 379-391.
  • Kurtz, S. (1999). "Nitrogen-activated transitions, level repulsion, and band gap reduction in GaAs1-xNx with x < 0.03," Phys. Rev. Lett. (82); pp. 3312-3315.
  • Kurtz, S.R.; Olson, J.M.; Friedman, D.J.; Kibbler, A.E.; Asher, S. (1994). "Ordering and Disordering of Doped Ga0.5In0.5P." J Electron Mater (23); pp. 431-435.
  • Kurtz, S.R.; Olson, J.M.; Arent, D.J.; Bode, M.H.; Bertness, K.A. (1994). "Low-Band-Gap Ga0.5In0.5P Grown on (511)B GaAs Substrates." J. Appl. Phys. (75); pp. 5110-5113.
  • Kurtz, S.R. (1993). "Anomalous Electroreflectance Spectrum of Spontaneously Ordered Ga0.5In0.5P." J. Appl. Phys (74); pp. 4130-4135.
  • Kurtz, S.R.; Olson, J.R.; Faine, P. (1991). "The difference between standard and average efficiencies of multijunction compared with single-junction concentrator cells." Solar Cells (30); p. 501.
  • Kurtz, S.R.; Olson, J. M.; Kibbler, A. (1990). "Effect of growth rate on the band gap of Ga0.5In0.5P." Appl. Phys. Lett (57); pp. 1922-1924.
  • Kurtz, S.R.; Faine, P.; Olson, J.M.; (1990). "Modeling of two-junction, series-connected tandem solar cells using top-cell thickness as an adjustable parameter." J. Appl. Phys (68); p. 1890.

Amorphous Silicon Solar Cells

  • Kurtz, S. R.; Gordon, R.G. (1987). "Transparent conducting electrodes on silicon." Solar Energy Materials (15); p. 229.
  • Kurtz, S.R.; Gordon, R. "Chemical vapor deposition of doped TiO2 thin films." Thin Solid Films (147); p. 167.
  • Kurtz, S.R.; Tsuo, Y.S.; Tsu, R. (1986). "Correlation of stress with light-induced defects in hydrogenated amorphous silicon films." Appl. Phys. Lett (49); p. 951.
  • Kurtz, S.R.; Gordon, R. (1986). "Chemical vapor deposition of titanium nitride at low temperatures." Thin Solid Films (140); p. 277.
  • Kurtz, S.R.; Proscia, J.; Gordon, R.G. (1986) "Chemical vapor deposition of hydrogenated amorphous silicon." J. Appl. Phys. (59); p. 249.

View all NREL publications for Dr. Kurtz.

Awards and Honors


  • Cherry Award, 2012
  • Dan David Prize (shared with Jerry Olson and James Hanson), Future category "Energy," 2007
  • National Science Foundation, graduate fellowship (1979-1985)


  • Space Technology Hall of Fame, 2004
  • The Scientific America 50 Award to NREL and Spectrolab for "Demonstrated photovoltaic cells with record-breaking high efficiencies." (see December, 2002 issue of Scientific American)
  • National Energy Resources Organization Award (2002)
  • Energy100 Award for the "Gallium Indium Phosphide/Gallium Arsenide / (Germanium) Monolithic, Series-Connected, Multi-Junction Solar Cells" (awarded to top 100 scientific accomplishments from the US Department of Energy,
  • R&D 100 Award, 2001 (GaInP2/GaAs/Ge triple junction solar cell)
  • Federal Laboratory Consortium for Technology Transfer Award, 1997
  • R&D 100 Award, 1990 (GaInP2/GaAs dual junction solar cell)


  • NREL outstanding Achievement Award for support of concentrator industry, 1998


  • NREL outstanding Achievement Award (for GaInP/GaAs cell), 1989