Black Silicon Enhanced Thin Film Silicon Photovoltaic Devices Page: 3 of 5
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DE-EE0000581
BLACK SILICON ENHANCED THIN FILM SILICON PHOTOVOLTAIC DEVICES
SiOnyx, Inc.
During this program we developed a Black Silicon enhanced thin film photovoltaic device. The
effort focused on 2 main material systems that are commonly used in the industry, amorphous
silicon solar cells and microcrystalline silicon solar cells.Although initially promising, we ran into a
fundamental challenge working with
hydrogenated amorphous silicon substrates. The
laser process is highly energetic and during laser
irradiation, pin holes and bubbles formed. After
extensive investigations into the cause of these
bubbles and holes we concluded that hydrogen
from the hydrogenated amorphous silicon was
outgassing and forming bubbles. Some of these
bubbles burst causing pin holes. After multiple
attempts to eliminate this effect by
dehydrogenating the amorphous prior to laser
processing failed we abandoned the amorphous
silicon path and focused on microcrystalline
films.
Microcrystalline cell developmentp.
Figure 2. Transmission optical image
showing Black Silicon at different laser
conditions. The region on the left was
processed with high power and we can
observe white light transmitting through pin
holes while at the optimum conditions
(center) the film is mostly black.We developed Black Silicon enhanced microcrystalline silicon cells. This work focused on
production quality microcrystalline p-i-n films from an industrial supplier. The laser process did
not form pin holes or bubbles in the films as was
observed with the amorphous silicon material
t'=-Lser Picse-e1 and
system. Therefore we were able to run laser An'es
process experiments to determine optimum laser - d
process parameters. In Figure 2 we have a laser
process experimental matrix. Optimum conditions
are shown in the middle region of the sample.
Optical characterization of these films using
absolute transmission and reflection measurements
revealed significant increases in optical absorption
with the addition of Black Silicon. Figure 3 shows Figure 3. Comparison of absorption
a comparison of the as deposited microcrystalline properties for laser processed verses as
film and the laser processed sample. In the visible deposited thin film junctions. Black
the absorption increased to 90% and in the near IR Silicon dramatically enhances
we pushed out the absorption past 1000 nm. This performance throughout the visible and
absorption improvement is essential to improve the IR regions of the spectrum.
performance of thin film silicon junctions.
We fabricated prototype thin crystalline Black Silicon solar cells as shown in Figure 4. The low
reflectivity of the Black Silicon material was maintained.Page 3 of 5
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Pralle, Martin U. & Carey, James E. Black Silicon Enhanced Thin Film Silicon Photovoltaic Devices, report, July 31, 2010; United States. (https://digital.library.unt.edu/ark:/67531/metadc1013871/m1/3/: accessed April 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.