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Nanomoulding of transparent zinc oxide electrodes for efficient light trapping in solar cells

Abstract

Nanopatterning has gained tremendous importance in the field of photovoltaics, as absorption of sunlight in solar cells can be enhanced drastically by proper engineering of photonic nanostructures1,2,3,4,5,6,7,8. However, despite intensive efforts, neither the ideal surface morphology nor the ideal scattering characteristics for optimum light trapping have been identified. Experimentally, a method capable of implementing arbitrarily designed surface morphologies directly into functional devices is desirable. Here, we establish a nanomoulding process that provides exactly such a platform, enabling precise, large-area, nanoscale patterning of functional zinc oxide films at low cost. We illustrate the application of nanomoulded zinc oxide films as transparent front electrodes in amorphous silicon solar cells, demonstrating excellent initial conversion efficiencies of 10.1%. In the quest to find the most efficient light-harvesting scheme, we anticipate that nanomoulding will catalyse the development and integration of exciting new nanophotonic structures.

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Figure 1: SEM images of master test structures and their corresponding nanomoulded ZnO replicas.
Figure 2: Schematic process flow for nanomoulding of ZnO.
Figure 3: Morphological fidelity analysis for ZnO nanomoulding.
Figure 4: Comparison of optical scattering properties.
Figure 5: Amorphous silicon solar cells on nanomoulded ZnO.

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Acknowledgements

The authors thank D. Alexander and M. Leboeuf for assistance with the FIB and AFM, respectively, W. Lee for providing the ATA master, Z. Holman and P. Cuony for careful proof-reading of the manuscript, and the Swiss Federal Energy Office and the Swiss National Science Foundation for funding (under project no. 101191 and grant no. 200021 12577/1).

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Contributions

C.B. conceived the nanomoulding method and coordinated the work. J.E. carried out the first nanomoulding experiments. K.S. fabricated the nanomoulded grating. M.C. deposited the silicon layers. C.B. characterized the nanomoulded ZnO, processed and measured the cells, performed the data analysis and wrote the manuscript. M.D. led the silicon layer development. F.-J.H. led the nanoimprinting activities. Ch.B. supervised the work.

Corresponding author

Correspondence to Corsin Battaglia.

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The authors declare no competing financial interests.

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Battaglia, C., Escarré, J., Söderström, K. et al. Nanomoulding of transparent zinc oxide electrodes for efficient light trapping in solar cells. Nature Photon 5, 535–538 (2011). https://doi.org/10.1038/nphoton.2011.198

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