Abstract
The origin of voltage deficits in polycrystalline cadmium selenide telluride (CdSeTe) solar cells is unclear. Here, we present a comprehensive voltage loss analysis performed on state-of-the-art CdSeTe devices—fabricated at Colorado State University and First Solar—using photoluminescence techniques, including external radiative efficiency (ERE) measurements. More specifically, we report the thermodynamic voltage limit Voc,ideal, internal voltage iVoc and external voltage Voc of partially and fully finished cells fabricated with different dopant species, dopant concentrations and back contacts. Arsenic-doped aluminium-oxide-passivated cells made at Colorado State University present remarkably high ERE (>1%)—translating into iVoc above 970 mV—but suffer from poor back-contact selectivity. On the other hand, arsenic-doped devices from First Solar present almost perfect carrier selectivity (Voc = iVoc), leading to Voc above 840 mV, and are limited by recombination in various parts of the device. Thus, development of contact structures that are both passivating and selective in combination with highly luminescent absorbers is key to reducing voltage losses.
This is a preview of subscription content, access via your institution
Access options
Access Nature and 54 other Nature Portfolio journals
Get Nature+, our best-value online-access subscription
$29.99 / 30 days
cancel any time
Subscribe to this journal
Receive 12 digital issues and online access to articles
$119.00 per year
only $9.92 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
Data availability
The authors declare that all data supporting the findings of this study are available within the paper and Supplementary Information files. First Solar’s data, beyond what is presented in the manuscript and the Supplementary Information, are proprietary and are not publicly available. Source data are provided with this paper.
References
Munshi, A. H. et al. Polycrystalline CdSeTe/CdTe absorber cells with 28 mA/cm2 short-circuit current. IEEE J. Photovolt. 8, 310–314 (2018).
Fiducia, T. A. M. et al. Understanding the role of selenium in defect passivation for highly efficient selenium-alloyed cadmium telluride solar cells. Nat. Energy 4, 504–511 (2019).
Kephart, J. M. et al. Sputter-deposited oxides for interface passivation of CdTe photovoltaics. IEEE J. Photovolt. 8, 587–593 (2018).
Amarasinghe, M. et al. Mechanisms for long carrier lifetime in Cd(Se)Te double heterostructures. Appl. Phys. Lett. https://doi.org/10.1063/5.0047976 (2021).
Kuciauskas, D. et al. Recombination velocity less than 100 cm/s at polycrystalline Al2O3/CdSeTe interfaces. Appl. Phys. Lett. https://doi.org/10.1063/1.5030870 (2018).
Kuciauskas, D. et al. in 47th IEEE Photovoltaic Specialists Conference 82–84 https://doi.org/10.1109/PVSC45281.2020.9300915 (IEEE, 2020).
McCandless, B. E. et al. Overcoming carrier concentration limits in polycrystalline CdTe thin films with in situ doping. Sci. Rep. 8, 14519 (2018).
Metzger, W. K. et al. Exceeding 20% efficiency with in situ group V doping in polycrystalline CdTe solar cells. Nat. Energy 4, 837–845 (2019).
Krasikov, D., Guo, D., Demtsu, S. and Sankin, I. Comparative study of As and Cu doping stability in CdSeTe absorbers. Sol. Energy Mater. Sol. Cells https://doi.org/10.1016/j.solmat.2021.111012 (2021).
Li, D.-B. et al. Low-temperature and effective ex situ group V doping for efficient polycrystalline CdSeTe solar cells. Nat. Energy 6, 715–722 (2021).
Liu, Z. et al. Open-circuit voltages exceeding 1.26 V in planar methylammonium lead iodide perovskite solar cells. ACS Energy Lett. 4, 110–117 (2018).
Kayes, B. M. et al. in 37th IEEE Photovoltaic Specialists Conference 4–8 https://doi.org/10.1109/PVSC.2011.6185831 (IEEE, 2011).
Smith, D. D. et al. Toward the practical limits of silicon solar cells. IEEE J. Photovolt. 4, 1465–1469 (2014).
Kanevce, A., Reese, M. O., Barnes, T. M., Jensen, S. A. and Metzger, W. K. The roles of carrier concentration and interface, bulk, and grain-boundary recombination for 25% efficient CdTe solar cells. J. Appl. Phys. https://doi.org/10.1063/1.4984320 (2017).
Duenow, J. N. et al. Relationship of open-circuit voltage to CdTe hole concentration and lifetime. IEEE J. Photovolt. 6, 1641–1644 (2016).
Munshi, A. H. et al. in 47th IEEE Photovoltaic Specialists Conference 1824–1828 https://doi.org/10.1109/PVSC45281.2020.9301003 (2020).
Sinton, R. A. & Cuevas, A. Contactless determination of current–voltage characteristics and minority‐carrier lifetimes in semiconductors from quasi‐steady‐state photoconductance data. Appl. Phys. Lett. 69, 2510–2512 (1996).
Cuevas, A. & Sinton, R. A. Prediction of the open-circuit voltage of solar cells from the steady-state photoconductance. Prog. Photovolt. Res. Appl. 5, 79–90 (1997).
Delamarre, A., Lombez, L. and Guillemoles, J.-F. Contactless mapping of saturation currents of solar cells by photoluminescence. Appl. Phys. Lett. https://doi.org/10.1063/1.3697704 (2012).
Katahara, J. K. & Hillhouse, H. W. Quasi-Fermi level splitting and sub-bandgap absorptivity from semiconductor photoluminescence. J. Appl. Phys. https://doi.org/10.1063/1.4898346 (2014).
Sarritzu, V. et al. Optical determination of Shockley-Read-Hall and interface recombination currents in hybrid perovskites. Sci. Rep. 7, 44629 (2017).
Stolterfoht, M. et al. The impact of energy alignment and interfacial recombination on the internal and external open-circuit voltage of perovskite solar cells. Energ. Environ. Sci. 12, 2778–2788 (2019).
Ruppel, W. & Würfel, P. Upper limit for the conversion of solar energy. IEEE Trans. Electron Devices 27, 877–882 (1980).
Shockley, W. & Queisser, H. J. Detailed balance limit of efficiency of p‐n junction solar cells. J. Appl. Phys. 32, 510–519 (1961).
Jean, J. et al. Radiative efficiency limit with band tailing exceeds 30% for quantum dot solar cells. ACS Energy Lett. 2, 2616–2624 (2017).
Vandewal, K., Tvingstedt, K., Gadisa, A., Inganas, O. & Manca, J. V. On the origin of the open-circuit voltage of polymer–fullerene solar cells. Nat. Mater. 8, 904–909 (2009).
Miller, O. D., Yablonovitch, E. & Kurtz, S. R. Strong internal and external luminescence as solar cells approach the Shockley–Queisser limit. IEEE J. Photovolt. 2, 303–311 (2012).
Würfel, P. and Würfel, U. Physics of Solar Cells: From Basic Principles to Advanced Concepts 3rd edn (Wiley-VCH, 2016).
Würfel, P. The chemical potential of radiation. J. Phys. C 15, 3967–3985 (1982).
Würfel, U., Cuevas, A. & Würfel, P. Charge carrier separation in solar cells. IEEE J. Photovolt. 5, 461–469 (2015).
Onno, A., Chen, C., Koswatta, P., Boccard, M. & Holman, Z. C. Passivation, conductivity, and selectivity in solar cell contacts: concepts and simulations based on a unified partial-resistances framework. J. Appl. Phys. 126, 183103 (2019).
Munshi, A. H. et al. Effect of CdCl2 passivation treatment on microstructure and performance of CdSeTe/CdTe thin-film photovoltaic devices. Sol. Energy Mater. Sol. Cells 186, 259–265 (2018).
Danielson, A. et al. in 46th IEEE Photovoltaic Specialists Conference 3018–3023 https://doi.org/10.1109/PVSC40753.2019.8980466 (IEEE, 2019).
Zhao, Y. et al. Monocrystalline CdTe solar cells with open-circuit voltage over 1 V and efficiency of 17%. Nat. Energy 1, 16067 (2016).
De Wolf, S., Descoeudres, A., Holman, Z. C. & Ballif, C. High-efficiency silicon heterojunction solar cells: a review. Green 2, 7–24 (2012).
Zhao, X.-H. et al. Determination of CdTe bulk carrier lifetime and interface recombination velocity of CdTe/MgCdTe double heterostructures grown by molecular beam epitaxy. Appl. Phys. Lett. https://doi.org/10.1063/1.4904993 (2014).
Zhao, X.-H. et al. Time-resolved and excitation-dependent photoluminescence study of CdTe/MgCdTe double heterostructures grown by molecular beam epitaxy. J. Vac. Sci. Technol. B https://doi.org/10.1116/1.4878317 (2014).
Moseley, J. et al. Impact of dopant-induced optoelectronic tails on open-circuit voltage in arsenic-doped Cd(Se)Te solar cells. J. Appl. Phys. https://doi.org/10.1063/5.0018955 (2020).
Grover, S. et al. in 44th IEEE Photovoltaic Specialists Conference 1193–1195 https://doi.org/10.1109/PVSC.2017.8366147 (IEEE, 2017).
Onno, A. et al. in 48th IEEE Photovoltaic Specialists Conference 1754–1757 https://doi.org/10.1109/PVSC43889.2021.9518829 (IEEE, 2021).
Green, M. A. & Ho-Baillie, A. W. Y. Pushing to the limit: radiative efficiencies of recent mainstream and emerging solar cells. ACS Energy Lett. 4, 1639–1644 (2019).
Moseley, J., Krasikov, D., Lee, C. and Kuciauskas, D. Diverse simulations of time-resolved photoluminescence in thin-film solar cells: A SnO2/CdSeyTe1−y case study. J. Appl. Phys. https://doi.org/10.1063/5.0063028 (2021).
Jundt, P., Kuciauskas, D. and Sites, J. in 47th IEEE Photovoltaic Specialists Conference 1408–1412 https://doi.org/10.1109/PVSC45281.2020.9300522 (IEEE, 2020).
Guillemoles, J.-F., Kirchartz, T., Cahen, D. & Rau, U. Guide for the perplexed to the Shockley–Queisser model for solar cells. Nat. Photonics 13, 501–505 (2019).
Green, M. et al. Solar cell efficiency tables (version 57). Prog. Photovolt. Res. Appl. 29, 3–15 (2020).
Dumbrell, R., Juhl, M. K., Trupke, T. & Hameiri, Z. Comparison of terminal and implied open-circuit voltage measurements. IEEE J. Photovolt. 7, 1376–1383 (2017).
Bivour, M. et al. in 33rd European PV Solar Energy Conference (eds Smets, A. et al.) (Curran Associates, 2018).
Grover, S. in 4th CdTe workshop (2020).
Kephart, J. M. et al. Band alignment of front contact layers for high-efficiency CdTe solar cells. Sol. Energy Mater. Sol. Cells 157, 266–275 (2016).
Swanson, D. E. et al. Single vacuum chamber with multiple close space sublimation sources to fabricate CdTe solar cells. J. Vac. Sci. Technol. A 34, 021202 (2016).
Zhao, Y., Zhao, X.-H. and Zhang, Y.-H. in 43rd IEEE Photovoltaic Specialists Conference 545–548 https://doi.org/10.1109/PVSC.2016.7749654 (IEEE, 2016)
Hegedus, S. S. & Shafarman, W. N. Thin-film solar cells: device measurements and analysis. Prog. Photovolt. Res. Appl. 12, 155–176 (2004).
Acknowledgements
The information, data or work presented herein was funded in part by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, under award numbers DE-EE0008552 (A.O., C.L., S.L., A.D., W.W., A.B., D.K., W.S. and Z.C.H.) and DE-EE0008557 (C.L. and W.S.). Funding was provided in part by the National Science Foundation under award no. 1846685 (Z.C.H.). This work was authored in part by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the US Department of Energy (DOE) under contract no. DE-AC36-08GO28308 (D.K.). The views expressed herein do not necessarily represent the views of the DOE or the US Government. The US Government retains and the publisher, by accepting the article for publication, acknowledges that the US Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for US Government purposes. We thank Y.-H. Zhang and his team at Arizona State University for building and providing access to the ERE measurement tool and J. Sites and his team at Colorado State University for building and providing access to the EQE and C–V measurement tools. We thank R. Pandey, T. Shimpi and J. Sites at Colorado State University, along with G. Yeung and C. Wolden at Colorado School of Mines, for providing some of the samples reported in this study. We thank 5N Plus for providing the CdTe, CdSeTe and CdCl2 source materials. First Solar authors acknowledge support from numerous colleagues and thank D. Martinez and K. Theis for sample preparation and analysis.
Author information
Authors and Affiliations
Contributions
A.O. and Z.C.H. conceived the project. A.O., C.R., A.D., S.G. and D.K. designed the methodology. A.O., C.R., S.L. and D.K. performed the formal analysis. A.O., C.R., S.L., A.D., W.W., A.B., S.G., J.B. and D.K. carried out the investigations. S.G., D.K., W.S. and Z.C.H. provided resources. A.O. wrote the original draft and A.O., C.R., A.D., A.B., S.G., D.K., W.S. and Z.C.H. reviewed and edited the manuscript. A.O. performed the visualization. D.K., W.S., G.X. and Z.C.H. supervised the project. A.O., D.K., W.S. and Z.C.H. acquired funding.
Corresponding authors
Ethics declarations
Competing interests
S.G., J.B. and G.X. work at First Solar, which is a publicly traded company that manufactures CdTe solar modules. Outside of this, the authors declare no competing interests.
Peer review
Peer review information
Nature Energy thanks the anonymous reviewers for their contribution to the peer review of this work.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary information
Supplementary Information
Supplementary Discussions 1–4, Methods 1–3, Tables 1–5 and Figs. 1–19.
Supplementary Data 1
Statistical source data for Supplementary Figs. 14 and 15 and Supplementary Tables 3–5.
Supplementary Data 2
Source data for Supplementary Fig. 9.
Supplementary Data 3
Statistical source data for Supplementary Fig. 11.
Supplementary Data 4
Time-resolved photoluminescence decays for samples shown in Fig. 2a,b and Supplementary Figs. 7 and 9.
Supplementary Data 5
Capacitance–voltage profiles for samples shown in Fig. 2b and Supplementary Figs. 9 and 19.
Source data
Source Data Fig. 2
Statistical source data for Fig. 2.
Source Data Fig. 3
Statistical source data for Fig. 3.
Source Data Fig. 4
Statistical source data for Fig. 4.
Rights and permissions
About this article
Cite this article
Onno, A., Reich, C., Li, S. et al. Understanding what limits the voltage of polycrystalline CdSeTe solar cells. Nat Energy 7, 400–408 (2022). https://doi.org/10.1038/s41560-022-00985-z
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/s41560-022-00985-z
This article is cited by
-
Resolving electron and hole transport properties in semiconductor materials by constant light-induced magneto transport
Nature Communications (2024)
-
20%-efficient polycrystalline Cd(Se,Te) thin-film solar cells with compositional gradient near the front junction
Nature Communications (2022)
-
Visualizing localized, radiative defects in GaAs solar cells
Scientific Reports (2022)
-
Contacts matter
Nature Energy (2022)