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Growth of LPCVD ZnO Bilayers for Solar Cell Front Electrodes
L. Ding, S. Nicolay, G. Bugnon, M. Benkhaira, C. Ballif
Transparent Conducting Oxides (TCO), Zinc Oxide, Bilayers
Thin Film Solar Cells
Subtopic: Amorphous and Microcrystalline Silicon Solar Cells
Event: 25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain
Session: 3AV.1.22
2943 - 2946
ISBN: 3-936338-26-4
Paper DOI: 10.4229/25thEUPVSEC2010-3AV.1.22
0,00 EUR
Document(s): paper


Front contact electrodes for thin film silicon (TF Si) solar cells have to combine properties of transparency, light scattering capacity and low resistivity. In this work, deposition of bilayers LPCVD ZnO is presented. Those bilayers consist in the combination of a highly doped plus a non-intentionally doped (nid) part, deposited in one growth step. The sheet resistance of the stack is found lower than the equivalent sheet resistance of the two independent layers. The bilayers are characterized by a total low electron density and low free carrier absorption (FCA), with remarkably high electron mobility (~34cm2/Vs) and haze factor (~30% at 600nm). This high mobility value is attributed to the diffusion of the boron from the highly doped layer into the top nid part, along the grain boundaries (GB). Hence, there is no sharp interface between the doped and nid parts. The bilayers and nid layer seem to have the same structure and GB density. Therefore, the high value of mobility compared to fully undoped case, is attributed to a screening of the GB potential barrier. Boron diffusion along the GB, from the seed doped layer, could explain this observation.