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Local Current Flow in Mixed-Phase Silicon Solar Cells and Correlation to Light-Induced Open-Circuit Voltage Enhancement

Published online by Cambridge University Press:  01 February 2011

Baojie Yan ,
C.-S. Jiang ,
H. R. Moutinho ,
M. M. Al-Jassim ,
Jeffrey Yang  and
Subhendu Guha
Baojie Yan
Affiliation:
byan@uni-solar.com, United Solar Ovonic Corp., Research and Development, 1100 West Maple Road, Troy, Michigan, 48306, United States, 248-519-5304, 248-362-4442
C.-S. Jiang
Affiliation:
Chun_Sheng_Jiang@nrel.gov, National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado, 80401, United States
H. R. Moutinho
Affiliation:
helio_moutinho@nrel.gov, National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado, 80401, United States
M. M. Al-Jassim
Affiliation:
mowafak_aljassim@nrel.gov, National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado, 80401, United States
Jeffrey Yang
Affiliation:
jyang@uni-solar.com, United Solar Ovonic Corporation, 1100 West Maple Road, Troy, Michigan, 48084, United States
Subhendu Guha
Affiliation:
sguha@uni-solar.com, United Solar Ovonic Corporation, 1100 West Maple Road, Troy, Michigan, 48084, United States
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Abstract

We use conductive atomic force microscopy (C-AFM) to measure the local current flow in the mixed-phase hydrogenated silicon n-i-p solar cell structure without the top ITO contact. The forward biased C-AFM images reveal that for the fully amorphous region the current is very low on the entire surface. However, high current spikes appear in the mixed-phase region, where the current spikes are correlated to the formation of nanocrystallite aggregations with a diameter of ~500 nm. Furthermore, the density of the current spikes increases from the mixed-phase to the substantially nanocrystalline regions. The nanocrystallite aggregation supports our previously proposed parallel-connected two-diode model for Voc drops with crystalline volume fraction and light-induced Voc increase in the mixed-phase solar cells. Adding a 50-nm thick a-Si:H buffer layer between the p and i layers significantly reduces the magnitude of the high current spikes, even the top morphology appears unaffected. This result is also consistent with the previously proposed two-diode model for explaining the carrier transport in the mixed-phase solar cells.

Keywords

amorphousnanostructurephotovoltaic
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 910: Symposium A – Amorphous and Polycrystalline Thin-Film Silicon Science and Technology – 2006 , 2006 , 0910-A23-06
Copyright
Copyright © Materials Research Society 2006

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