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@PHDTHESIS{Mai:58946,
author = {Mai, Yaohua},
title = {{M}icrocrystalline silicon layers for thin film solar cells
prepared with {H}ot {W}ire {C}hemical {V}apour {D}eposition
and {P}lasma {E}nhanced {C}hemical {V}apour {D}eposition},
volume = {4254},
issn = {0944-2952},
school = {VR Chin. Tianjin},
type = {Dr. (Univ.)},
address = {Jülich},
publisher = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
reportid = {PreJuSER-58946, Juel-4254},
series = {Berichte des Forschungszentrums Jülich},
pages = {144 p.},
year = {2007},
note = {Record converted from VDB: 12.11.2012; Tianjin, VR China,
Nankai Univ., Diss., 2006},
abstract = {High rate growth process, material quality and related
solar cell performance of hydrogenated microcrystalline
silicon ($\mu$c-Si:H) were investigated in this work. High
deposition rate (R$_{D}$) was achieved by very high
frequency (VHF) plasma-enhanced chemical vapor deposition
(PECVD) working at high pressure and high power (hphP).
Compared to the $\mu$c-Si:H material deposited with
conventional low pressure, low power (lplP), the hphP films
showed equivalent optical and electrical properties,
indicating their abilities as absorbers in thin film silicon
solar cells. The influences of the deposition parameters on
the solar cell deposition rate and performance were
systematically investigated in this thesis. It was found
that optimum cells were always found close to the transition
from highly microcrystalline to the amorphous growth and
with medium crystallinity. Variations of many deposition
parameters can tune the crystallinity. Among them, varying
silane concentration (SC) is the most easy and
straightforward way. Under optimized conditions, high
efficiency of 9.8\% was obtained at RD over 1 nm/s for a
single junction p-i-n solar cell. Efforts were also made to
find out the correlation between the material properties and
solar cell performance. The Raman structure depth profile
method revealed that hphP solar cells consisted of a more
amorphous incubation layer at the p/i interface, which was
found to reduce the short wavelength light response of the
solar cells. Besides PECVD, Hot Wire (HW) CVD is an
alternative method for $\mu$c-Si:H deposition. It was found
that HWCVD $\mu$c-Si H cells showed higher V$_{OC}$ and FF
than the PECVD cells in a wide range of i-layer
crystallinity. This was attributed to the better p/i
interface quality in the HWCVD cells. Inserting an intrinsic
microcrystalline p/i interface layer deposited by HWCVD into
PECVD cells nearly eliminated the above differences. Raman
structure depth profile, transmission electron microscopy
and selective area electron diffraction were applied to
investigate the structure properties of the solar cells.
However, differences could hardly be found in the already
homogeneous i-layers of PECVD and HWCVD cells. Thus the
positive effect of the HW-buffer for facilitating nucleation
was not observed. An amorphous HW-buffer layer in PECVD
cells resulted in a more amorphous p/i interface and an
increasing crystallinity along the growth axis. However,
such amorphous interface layer still enhanced the V$_{OC}$
and FF of the resulting cells. Therefore, it was concluded
that structure homogeneity was not the reason for the better
performance of the HWCVD cells. Applying the HW-buffer
concept to the PECVD hphP cells, we obtained a high
efficiency of 10.3\% at a high R$_{D}$ of 1.1 nm/s. This is
the highest efficiency reported so far for the single
junction $\mu$c-Si:H solar cells in p-i-n configuration.},
cin = {IEF-5},
cid = {I:(DE-Juel1)VDB813},
pnm = {Erneuerbare Energien},
pid = {G:(DE-Juel1)FUEK401},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
url = {https://juser.fz-juelich.de/record/58946},
}