- Physical Review Journals
All JournalsPhysics Magazine

PRX Energy

Reuse & Permissions

It is not necessary to obtain permission to reuse this article or its components as it is available under the terms of the Creative Commons Attribution 4.0 International license. This license permits unrestricted use, distribution, and reproduction in any medium, provided attribution to the author(s) and the published article's title, journal citation, and DOI are maintained. Please note that some figures may have been included with permission from other third parties. It is your responsibility to obtain the proper permission from the rights holder directly for these figures.

Export citation

Export citation

Choose format for download:

Download Citation
  • Open Access

Performance Modeling of Tandem Photovoltaics: A Yearlong Outdoor Degradation Analysis of a GaAs//Si Minimodule

Martin Springer*, Robert Witteck, Timothy J. Silverman, John F. Geisz, William E. McMahon, and Emily L. Warren

  • *Contact author: martin.springer@nlr.gov
PDF

PRX Energy 5, 023014 – Published 18 June, 2026

DOI: https://doi.org/10.1103/cmw1-vsbd

Abstract

We present a performance modeling and degradation analysis framework for tandem photovoltaic modules, building upon established procedures for crystalline silicon devices and adapting them to account for the spectral sensitivity of multijunction technologies. The methodology employs filter criteria to select outdoor measurements close to standard test conditions (STC) under stable spectral and ambient conditions, followed by normalization of power production data with corrections for temperature, irradiance, and precipitable water vapor. We demonstrate this framework using a mechanically stacked four-terminal gallium arsenide (GaAs) // silicon (Si) tandem solar minimodule deployed outdoors from October 2019 to January 2021 in Golden, Colorado, USA. We determined degradation rates of −4.1±0.2%/year for the GaAs subcell and −2.5±0.9%/year for the Si subcell, with analysis of individual performance metrics indicating that packaging degradation, particularly delamination, was the dominant failure mode. Simulations using PVcircuit, an open-source equivalent-circuit solver, confirmed these findings. The presented methodology provides a reproducible foundation for performance modeling and degradation analysis of emerging tandem technologies.

View figure in article

Physics Subject Headings (PhySH)

Popular Summary

Tandem solar cells stack two absorbing layers to capture more of the solar spectrum than conventional single-junction solar cells. However, no standardized method currently exists to evaluate how quickly these devices degrade under real outdoor conditions. Here, the authors developed a systematic framework that filters field measurements for stable atmospheric conditions and corrects for variations in temperature, irradiance, and spectral content. They applied this method to a gallium arsenide/silicon tandem mini-module deployed outdoors in Colorado for 14 months. The analysis reveals that the dominant source of performance loss was degradation of the module packaging, specifically delamination, rather than the semiconductor cells themselves. Circuit-level simulations independently confirmed this conclusion. These results demonstrate that reliable packaging is as critical as cell efficiency for emerging tandem technologies. The freely available methodology provides a reproducible foundation for outdoor performance evaluation of any tandem architecture, supporting the durability assessments needed for commercial deployment.

Article Text

References (43)

  1. P. Bojek, Solar PV—Analysis, https://www.iea.org/reports/solar-pv (2022).
  2. D. Feldman, K. Dummit, J. Zuboy, and R. Margolis, Spring 2023 Solar Industry Update, Tech. Rep. [National Renewable Energy Laboratory (NREL), Golden, Colorado, 2023].
  3. S. Schäfer and R. Brendel, Accurate calculation of the absorptance enhances efficiency limit of crystalline silicon solar cells with Lambertian light trapping, IEEE J. Photovolt. 8, 1156 (2018).
  4. Y. Chen, D. Chen, P. P. Altermatt, S. Zhang, L. Wang, X. Zhang, J. Xu, Z. Feng, H. Shen, and P. J. Verlinden, Technology evolution of the photovoltaic industry: Learning from history and recent progress, Prog. Photovolt.: Res. Appl. 31, 1194 (2023).
  5. N. M. Haegel et al., Photovoltaics at multi-terawatt scale: Waiting is not an option, Science 380, 39 (2023).
  6. ITRPV, International Technology Roadmap for Photovoltaic (ITRPV): 2022 Results, 14th Edition, Tech. Rep. (VDMA, 2023).
  7. I. Almansouri, A. Ho-Baillie, S. P. Bremner, and M. A. Green, Supercharging silicon solar cell performance by means of multijunction concept, IEEE J. Photovolt. 5, 968 (2015).
  8. R. E. Brock, P. Hebert, J. Ermer, and R. H. Dauskardt, Degradation of multijunction photovoltaic gridlines induced via thermal cycling, Sol. Energy Mater. Sol. Cells 179, 178 (2018).
  9. D. C. Jordan and S. R. Kurtz, Photovoltaic degradation rates—an analytical review, Prog. Photovolt.: Res. Appl. 21, 12 (2013).
  10. IEC 62670-3: 2017. Photovoltaic concentrators (CPV) - Performance testing - Part 3: Performance measurements and power rating. Geneva: International Electrotechnical Commission.
  11. M. Steiner and G. Siefer, Translation of outdoor tandem PV module I–V measurements to a STC power rating, Prog. Photovolt.: Res. Appl. 31, 862 (2023).
  12. R. Witteck, D. Nguyen Minh, G. Paul, S. P. Harvey, X. Zheng, Q. Jiang, M. Chen, T. Abzieher, A. F. Palmstrom, B. Habersberger, E. A. Gaulding, J. M. Luther, and L. M. Wheeler, Reducing thermal degradation of perovskite solar cells during vacuum lamination by internal diffusion barriers, ACS Appl. Energy Mater. 7, 10750 (2024).
  13. J. Geisz, E. Warren, and W. McMahon, PVcircuit, (2022).
  14. S. Essig, C. Allebé, T. Remo, J. F. Geisz, M. A. Steiner, K. Horowitz, L. Barraud, J. S. Ward, M. Schnabel, A. Descoeudres, D. L. Young, M. Woodhouse, M. Despeisse, C. Ballif, and A. Tamboli, Raising the one-sun conversion efficiency of III–V/Si solar cells to 32.8% for two junctions and 35.9% for three junctions, Nat. Energy 2, 17144 (2017).
  15. M. Rienäcker, E. L. Warren, M. Schnabel, H. Schulte-Huxel, R. Niepelt, R. Brendel, P. Stradins, A. C. Tamboli, and R. Peibst, Back-contacted bottom cells with three terminals: Maximizing power extraction from current-mismatched tandem cells, Prog. Photovolt. Res. Appl. 27, 410 (2019).
  16. K. T. VanSant, A. C. Tamboli, and E. L. Warren, III-V-on-Si tandem solar cells, Joule 5, 514 (2021).
  17. R. C. Whitehead, K. T. VanSant, E. L. Warren, J. Buencuerpo, M. Rienäcker, R. Peibst, J. F. Geisz, and A. C. Tamboli, Optimization of four terminal rear heterojunction GaAs on Si interdigitated back contact tandem solar cells, Appl. Phys. Lett. 118, 6 (2021).
  18. F. Haase, B. Min, C. Hollemann, J. Krügener, R. Brendel, and R. Peibst, Fully screen-printed silicon solar cells with local Al-p+ and n-type POLO interdigitated back contacts with a VOC of 716 mV and an efficiency of 23%, Prog. Photovolt.: Res. Appl. 29, 516 (2021).
  19. T. Stoffel and A. Andreas, NREL Solar Radiation Research Laboratory (SRRL): Baseline Measurement System (BMS); Golden, Colorado (Data), Tech. Rep. (National Renewable Energy Lab., Golden, Colorado), 1981).
  20. B. Marion, in 2008 33rd IEEE Photovoltaic Specialists Conference, San Diego, CA, USA (2008), pp. 1–6.
  21. D. C. Jordan, C. Deline, S. R. Kurtz, G. M. Kimball, and M. Anderson, Robust PV degradation methodology and application, IEEE J. Photovolt. 8, 525 (2018).
  22. IEC 61724-1: 2021. Photovoltaic system performance - Part 1: Monitoring. Geneva: International Electrotechnical Commission.
  23. T. J. Silverman, M. G. Deceglie, B. Marion, S. Cowley, B. Kayes, and S. Kurtz, in 2013 IEEE 39th Photovoltaic Specialists Conference (PVSC) (IEEE, Tampa, FL, 2013), pp. 0103–0108.
  24. S. P. Philipps, G. Peharz, R. Hoheisel, T. Hornung, N. M. Al-Abbadi, F. Dimroth, and A. W. Bett, Energy harvesting efficiency of III–V triple-junction concentrator solar cells under realistic spectral conditions, Sol. Energy Mater. Sol. Cells 94, 869 (2010).
  25. D. L. King, W. E. Boyson, and J. A. Kratochvil, Photovoltaic Array Performance Model, Tech. Rep. SAND2004-3535 [Sandia National Laboratories (SNL), Albuquerque, New Mexico and Livermore, California, 2004].
  26. X. Dang, H. Peng, X. Wang, and H. Zhang, Theil-Sen estimators in a multiple linear regression model, (2009), https://home.olemiss.edu/∼xdang/papers/MTSE.pdf.
  27. D. C. Jordan, M. G. Deceglie, and S. R. Kurtz, in 2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC) Portland, OR, USA (2016), pp. 0273–0278.
  28. J. F. Geisz, M. A. Steiner, I. Garcia, R. M. France, W. E. McMahon, C. R. Osterwald, and D. J. Friedman, Generalized optoelectronic model of series-connected multijunction solar cells, IEEE J. Photovolt. 5, 1827 (2015).
  29. J. F. Geisz, W. E. McMahon, J. Buencuerpo, M. S. Young, M. Rienäcker, A. C. Tamboli, and E. L. Warren, Characterization of multiterminal tandem photovoltaic devices and their subcell coupling, Cell Rep. Phys. Sci. 2, 100677 (2021).
  30. U. Rau, B. Blank, T. C. M. Müller, and T. Kirchartz, Efficiency potential of photovoltaic materials and devices unveiled by detailed-balance analysis, Phys. Rev. Appl. 7, 044016 (2017).
  31. E. E. Perl, J. Simon, J. F. Geisz, M. L. Lee, D. J. Friedman, and M. A. Steiner, Measurements and modeling of III-V solar cells at high temperatures up to 400 ∘C, IEEE J. Photovolt. 6, 1345 (2016).
  32. R. Witteck, J. F. Geisz, E. L. Warren, and W. E. McMahon, Spectral effects on the energy harvesting efficiency of two- and four-terminal tandem photovoltaics, Solar RRL 8, 2300782 (2024).
  33. S. Essig, M. A. Steiner, C. Allebé, J. F. Geisz, B. Paviet-Salomon, S. Ward, A. Descoeudres, V. LaSalvia, L. Barraud, N. Badel, A. Faes, J. Levrat, M. Despeisse, C. Ballif, P. Stradins, and D. L. Young, Realization of GaInP/Si dual-junction solar cells with 29.8% 1-sun efficiency, IEEE J. Photovolt. 6, 1012 (2016).
  34. N. Martin and J. M. Ruiz, Calculation of the PV modules angular losses under field conditions by means of an analytical model, Sol. Energy Mater. Sol. Cells 70, 25 (2001).
  35. M. Aghaei, A. Fairbrother, A. Gok, S. Ahmad, S. Kazim, K. Lobato, G. Oreski, A. Reinders, J. Schmitz, M. Theelen, P. Yilmaz, and J. Kettle, Review of degradation and failure phenomena in photovoltaic modules, Renew. Sustain. Energy Rev. 159, 112160 (2022).
  36. J. A. D. Cueto and B. Von Roedern, Long-term transient and metastable effects in cadmium telluride photovoltaic modules, Prog. Photovolt.: Res. Appl. 14, 615 (2006).
  37. K. Sinapis, G. Papageorgiou, K. Durose, M. Van Den Donker, and W. Folkerts, in 2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC) (IEEE, New Orleans, LA, 2015), pp. 1–5.
  38. P. Hacke, M. Owen-Bellini, M. D. Kempe, D. B. Sulas-Kern, D. C. Miller, M. Jankovec, S. Mitterhofer, M. Topič, S. Spataru, W. Gambogi, and T. Tanahashi, Acceleration factors for combined-accelerated stress testing of photovoltaic modules, Solar RRL 7, 2300068 (2023).
  39. M. Köntges, G. Oreski, U. Jahn, M. Herz, P. Hacke, and K.-A. Weiß, Assessment of Photovoltaic Module Failures in the Field: International Energy Agency Photovoltaic Power Systems Programme: IEA PVPS Task 13, Subtask 3: Report IEA-PVPS T13-09:2017 (International Energy Agency, 2017).
  40. J. Pascual, M. García, J. Marcos, and L. Marroyo, Analysis of polyamide and fluoropolymer backsheets: Degradation and insulation failure in field-aged photovoltaic modules, Prog. Photovolt.: Res. Appl. 31, 494 (2023).
  41. T. J. Silverman, M. G. Deceglie, I. Repins, M. Owen-Bellini, J. J. Berry, J. S. Stein, and L. T. Schelhas, Durability research is pivotal for perovskite photovoltaics, Nat. Energy 10, 934 (2025).
  42. M. Deceglie, K. Anderson, A. B. Shinn, C. Deline, N. Ambarish, M. Mikofski, J. Yan, K. Perry, S. Villamar, and W. Vining, NLR/rdtools: Version 2.1.7, 2023, https//doi.org/10.5281/zenodo.4291128
  43. M. Springer, R. Witteck, T. J. Silverman, J. F. Geisz, W. E. McMahon, and E. L. Warren, Outdoor deployment data for a four-terminal GaAs//Si tandem solar mini-module, (2026), NLR Data Catalog. https//doi.org/10.7799/3026700

Outline

Information

PRX Energy 5, 023014– Published 18 June, 2026
  • Received 11 March 2025
  • Revised 18 March 2026
  • Accepted 1 April 2026
Crossmark - Check for updates button
Creative Commons Logo

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Open access publication funded by National Laboratory of the Rockies (NLR), part of a national laboratory of the U.S. Department of Energy.

Published by the American Physical Society

Sign In to Your Journals Account

Filter

Filter

Article Lookup

Enter a citation