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High-Rate Plasma Process for Microcrystalline Silicon: Over 9% Efficiency Single Junction Solar Cells

Published online by Cambridge University Press:  21 March 2011

Takuya Matsui ,
Akihisa Matsuda  and
Michio Kondo
Takuya Matsui
Affiliation:
Research Center for Photovoltaics, National Institute of Advanced Industrial Science and Technology (AIST) 1-1-1 Umezono, Tsukuba, 305-8568, Japan
Akihisa Matsuda
Affiliation:
Research Center for Photovoltaics, National Institute of Advanced Industrial Science and Technology (AIST) 1-1-1 Umezono, Tsukuba, 305-8568, Japan
Michio Kondo
Affiliation:
Research Center for Photovoltaics, National Institute of Advanced Industrial Science and Technology (AIST) 1-1-1 Umezono, Tsukuba, 305-8568, Japan
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Abstract

This paper presents microcrystalline silicon (μ c-Si:H) p-i-n (superstrate-type) solar cells fabricated by 100 MHz plasma-enhanced chemical vapor deposition (PECVD) at i-layer deposition rates of >2 nm/s. Under high-rate conditions, in particular, the deposition pressure is found to play a dominant role in determining short circuit current (Jsc) of solar cell. With anincrease in deposition pressure from 3 to 7-9 Torr, Jsc increases by more than 50% due to a significant improvement in the long wavelength (>600 nm) responses, which essentially leads to high efficiency (∼8%) solar cells in the 2-3 nm/s deposition rate range. Further progress in solar cell efficiency has been made by the improvement of TCO/p and p/i interfaces. As a result, efficiency reaches 9.13% (Jsc=23.7 mA/cm2,Voc=0.528 V,FF=0.73) with a 2.3μm-thick i-layer grown at 2.3 nm/s. Transmission electron microscopy and secondary-ion mass spectroscopy studies reveal that samples prepared at lower pressure (∼4 Torr) comprise many grain boundaries due to disordered grain growth, which induces an anomalous incorporation of atmospheric impurities (predominantly oxygen) after exposing sample to air. In contrast, the high-pressure process (<7 Torr) provides denser grain columns coalesced with [110]-oriented crystallites, which in turn inhibits impurities from penetrating deeper in the film. Based on above results, we propose that the less post-oxidation behavior associated with the denser microstructure of high-pressure-grown μc-Si:H is responsible for the excellent charge collection in p-i-n solar cells.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 808: Symposium A – Amorphous and Nanocrystaline Silicon Science and Technology-2004 , 2004 , A8.1
Copyright
Copyright © Materials Research Society 2004

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References

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