A Low Resistance Calcium/Reduced Titania Passivated Contact for High Efficiency Crystalline Silicon Solar Cells

Abstract
Recent advances in the efficiency of crystalline silicon (c-Si) solar cells have come through the implementation of passivated contacts that simultaneously reduce recombination and resistive losses within the contact structure. In this contribution, low resistivity passivated contacts are demonstrated based on reduced titania (TiOx) contacted with the low work function metal, calcium (Ca). By using Ca as the overlying metal in the contact structure we are able to achieve a reduction in the contact resistivity of TiOx passivated contacts of up to two orders of magnitude compared to previously reported data on Al/TiOx contacts, allowing for the application of the Ca/TiOx contact to n-type c-Si solar cells with partial rear contacts. Implementing this contact structure on the cell level results in a power conversion efficiency of 21.8% where the Ca/TiOx contact comprises only ≈6% of the rear surface of the solar cell, an increase of 1.5% absolute compared to a similar device fabricated without the TiOx interlayer.

Citation
Allen TG, Bullock J, Jeangros Q, Samundsett C, Wan Y, et al. (2017) A Low Resistance Calcium/Reduced Titania Passivated Contact for High Efficiency Crystalline Silicon Solar Cells. Advanced Energy Materials: 1602606. Available: http://dx.doi.org/10.1002/aenm.201602606.

Acknowledgements
This work was supported by the Australian government through the Australian Renewable Energy Agency (ARENA). Work at the University of California, Berkeley was supported by the Bay Area Photovoltaic Consortium (BAPVC). The authors would like to acknowledge Sorin Lazar for his help with monochromated EELS experiments and the Interdisciplinary Centre For Electron Microscopy of EPFL for the use of their microscope.

Publisher
Wiley

Journal
Advanced Energy Materials

DOI
10.1002/aenm.201602606

Additional Links
http://onlinelibrary.wiley.com/doi/10.1002/aenm.201602606/fullhttp://minerva-access.unimelb.edu.au/bitstreams/4d6f93d5-8ef2-5193-a438-ca01403dda37/download

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