| Thin Film Silicon Solar Module |
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Amorphous Silicon Thin Film
Solar Cells
Although the technology of manufacturing
amorphous silicon (a-Si) thin-film solar cells has been well developed
for more than three decades, the large-area a-Si thin-film solar
cells with high efficiency can be implemented only recently by the
improvement of the large-scale coating and deposition technologies.
In fact, the microstructure of the a-Si solar cell is very simple
as a consequence of the nature of photovoltaic mechanism. The schematic
diagram of the structure is illustrated in Fig. 1. Upon the glass
substrate, the functionality of power generation can be achieved
through the front electrode (TCO layer), the p-i-n active layer,
and the back contact as a back electrode of the cell. The rough surfaces
of both TCO layer and back contact can enhance light absorption via
the light trapping effect after sunlight is incident into the solar
cell from the glass side. |
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Amorphous Silicon/Microcrystalline
Silicon Thin Film Solar Cells
The efficiency of thin-film silicon
solar cells can be increased by the deposition of the second active
layer with microcrystalline silicon (μc-Si) p-i-n layers. The degree
of the micro-crystallization is determined by H2 dilution during
chemical vapor deposition under appropriate conditions. Because of
the micro-crystallization, the life time of the carriers in this
μc-Si layer can be enlarged. The other reason why the efficiency
of a-Si/ μc-Si is higher than that of the single-layer a-Si solar
cell is that the absorption spectrum of the tandem cell can cover
both of the ranges of infrared and visible light. Therefore the usage
of the sunlight energy in a tandem cell is much better than that
in a single-layer a-Si solar cell.
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