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Highly efficient Cu(In,Ga)Se2 solar cells grown on flexible polymer films

Abstract

Solar cells based on polycrystalline Cu(In,Ga)Se2 absorber layers have yielded the highest conversion efficiency among all thin-film technologies1,2,3, and the use of flexible polymer films as substrates offers several advantages in lowering manufacturing costs. However, given that conversion efficiency is crucial for cost-competitiveness, it is necessary to develop devices on flexible substrates that perform as well as those obtained on rigid substrates. Such comparable performance has not previously been achieved, primarily because polymer films require much lower substrate temperatures during absorber deposition, generally resulting in much lower efficiencies4. Here we identify a strong composition gradient in the absorber layer as the main reason for inferior performance and show that, by adjusting it appropriately, very high efficiencies can be obtained. This implies that future manufacturing of highly efficient flexible solar cells could lower the cost of solar electricity and thus become a significant branch of the photovoltaic industry.

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Figure 1: Electronic and optical structure of CIGS solar cells.
Figure 2: Deposition processes, optoelectronic properties, and composition profile analysis.
Figure 3: Temperature-dependent current–voltage measurements and simulations.
Figure 4: Illustration of the electronic barrier.

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Acknowledgements

This work was supported by the Swiss National Science Foundation, the Swiss Federal Office of Energy, the European FP7 Project ‘hipo-CIGS’, and the Commission for Technology and Innovation, Switzerland.

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A.C., S.B., F.P., P.B., S.S., S.N., Y.E.R. and A.N.T. designed the research and experiments. A.C. and P.B. fabricated the solar cells. A.C., S.B., F.P., C.G., A.R.U., C.F., L.K., J.P., R.V., G.B. and A.N.T. performed the characterization, simulation and analysis. A.C., S.B., C.G. and A.N.T. wrote the paper. All authors contributed to discussions.

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Correspondence to Adrian Chirilă.

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The authors declare no competing financial interests.

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Chirilă, A., Buecheler, S., Pianezzi, F. et al. Highly efficient Cu(In,Ga)Se2 solar cells grown on flexible polymer films. Nature Mater 10, 857–861 (2011). https://doi.org/10.1038/nmat3122

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