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CdTe solar cells with open-circuit voltage breaking the 1 V barrier

A Corrigendum to this article was published on 11 April 2016

Abstract

CdTe solar cells have the potential to undercut the costs of electricity generated by other technologies, if the open-circuit voltage can be increased beyond 1 V without significant decreases in current. However, in the past decades, the open-circuit voltage has stagnated at around 800–900 mV. This is lower than in GaAs solar cells, even though GaAs has a smaller bandgap; this is because it is more difficult to achieve simultaneously high hole density and lifetime in II–VI materials than in III–V materials. Here, by doping the CdTe with a Group V element, we report lifetimes in single-crystal CdTe that are nearly radiatively limited and comparable to those in GaAs over a hole density range relevant for solar applications. Furthermore, the deposition on CdTe of nanocrystalline CdS layers that form non-ideal heterointerfaces with 10% lattice mismatch impart no damage to the CdTe surface and show excellent junction transport properties. These results enable the fabrication of CdTe solar cells with open-circuit voltage greater than 1 V.

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Figure 1: Non-ideal interfaces in thin-film technologies.
Figure 2: CdTe lifetimes and hole densities comparable to GaAs.
Figure 3: High-resolution imaging of a high-performance, lattice-mismatched interface.
Figure 4: Low surface recombination occurs across a true lattice-mismatched heterojunction.
Figure 5: Overcoming the historical voltage barrier.

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Acknowledgements

The work at NREL and Washington State University is supported by the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, under Contract No. DE-AC36-08GO28308. This research was supported, in part, by Oak Ridge National Laboratory’s Center for Nanophase Materials Sciences, where part of the TEM work was performed, which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, DOE, in collaboration with R. R. Unocic. Other parts of the TEM work were performed at the LeRoy Eyring Center for Solid State Science at Arizona State University in collaboration with T. Aoki. The X-ray diffraction experiments were performed at the University of Tennessee, Knoxville, using instruments procured through the general infrastructure grant of the DOE-Nuclear Energy University Program (DE-NE0000693).

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J.M.B., J.N.D., E.C. and D.S.A. established anion doping and fabricated devices. M.O.R. developed surface cleaning and passivation methods. J.A.A., M.K.P., C.-S.J. and M.M.A.-J. directed and executed aberration-corrected STEM, HAADF, EELS, AFM, SKPM, SEM and EDS. D.K. performed two-photon excitation time-correlated single-photon counting. S.S., T.A. and K.G.L. made crystals. W.K.M., J.N.D., D.S.A. and J.M.B. directed research. All authors discussed the results and contributed to the manuscript.

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Correspondence to W. K. Metzger.

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Supplementary Figures 1–2, Supplementary Tables 1–2. (PDF 586 kb)

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Burst, J., Duenow, J., Albin, D. et al. CdTe solar cells with open-circuit voltage breaking the 1 V barrier. Nat Energy 1, 16015 (2016). https://doi.org/10.1038/nenergy.2016.15

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