S. Bauer et al., P-I INTERFACE ENGINEERING AND I-LAYER CONTROL OF HOT-WIRE A-SI-H BASED P-I-N SOLAR-CELLS USING IN-SITU ELLIPSOMETRY, Solar energy materials and solar cells, 43(4), 1996, pp. 413-424
In this paper we report on the effect of monitoring the i-layer region
near the p-i interface with the help of in-situ kinetic and spectrosc
opic ellipsometry on the performance of hot-wire deposited hydrogenate
d amorphous silicon p-i-n solar cells. It is very clearly observed tha
t the microstructure at the p-i interface region in terms of the Si-Si
bond packing density and surface roughness significantly affects the
cell performance. The filament temperature, T-Fil, Was the main parame
ter varied to control the above mentioned two properties near the p-i
interface as well as in the bulk i-layer. In order to achieve signific
ant enhancement in the cell performance we extended the idea of the ''
soft start'', earlier employed for the glow discharge deposited solar
cells, to the hot-wire deposited i-layer. We were able to control the
i-layer properties at the p-i interface and in the bulk independently
and correlate these to the cell performance. It is shown that a major
increase in cell performance can be achieved by improving the microstr
ucture of the growing film directly at the p-i interface. Most interes
tingly, no significant deterioration in cell efficiency has been obser
ved if only the p-i interface was properly controlled but the i-layer
was of lower quality. These results are also shown to be consistent wi
th model calculations of a numerical simulation. Our results therefore
provide a clue to prepare hot-wire a-Si:H based solar cells with high
efficiency and in the whole at high growth rates, which is needed for
a more economic a-Si:H solar cell production.