Transcript Poster Template - Missouri S&T

Microlens Array Light Trapping CdTe Solar Cells for use in
Concentrator Photovoltaics
Student: Patrick Margavio, Mechanical and Aerospace Engineering
Why Solar?
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Current energy usage of the world’s 6.5 billion people is 13 Terawatts1
The sun outputs 120,000 TW
Globally extractable wind power is 4 TW
With current efficiencies, fraction of land required to supply present
energy consumption is 1.35% of Earth’s landmass2
• Amount required for food production is 13% cultivation, 26% pasture2
What’s a Microlens Array?
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Faculty Advisor: Dr. Hailung Tsai, Mechanical and Aerospace Engineering
What is Light Trapping?
Why Concentrate Solar Energy?
There are two basic strategies to compete with fossil fuels
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Make solar inexpensive
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There are two basic ways to trap light within a solar cell
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Copper indium gallium diselenide, dye sensitized solar
Commercially available single and polycrystalline silicon
Solar houses on campus
Reducing the amount of light reflected away from top surface
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Examples below scatter incoming light to reduce reflection3
Preventing light from leaving once it has entered
Maximize efficiency
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Combine solar cell (like multijunction GaAs) with solar concentrator
Mirrors, Luminescent Solar Concentrators
Solar cell is 75% of cost of system
A microlens array is a collection of microscopic lenses
assembled in an orderly pattern
Focuses light into a periodic pattern
Two purposes for us
• Light less likely to reflect off top surface
• Incident light intensity increased locally
Efficiency increases with increased intensity
CdTe Cell Fabrication:
• Transparent Conducing Oxide (TCO) purchased from
Pilkington (TEC C10)
• 150 nm CdS film chemically deposited on TCO
• 5 µm CdTe film deposited on CdS
• Sample dipped in CdCl2
• Sample rinsed with methanol
Demonstration Model
• We will implement our solar cell design to power a small
electronic device
• A two square inch solar cell can
produce around 10 to 11 W of
power (based on commercially
available silicon solar technology)
Making the Silicon Microlens Array:
Making the Microlens Array Mold:
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The silicon gel used is Polydimethylsiloxane (PDMS)
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PDMS is combined with a curing agent
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The PDMS mixture is poured over the glass mold
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Sample is placed in a vacuum
chamber (right) to remove bubbles
from mixing process
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Next PDMS is cured at 700C for
one hour in a furnace to solidify
It is expensive to create
microlens arrays
Decrease expense by creating
a Foturan glass mold and then
using it to make many cheap
silicon films
Mold is created by laser
machining
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G code used to computer
control process is shown
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After laser machining Foturan
glass is baked at 5000C and
then at 6000C.
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After baking, sample is etched
with HF acid
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After etching sample is
annealed for another hour
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To left, a microscope image
of the silicon film is visible.
Below, the glass mold is
shown in the silicon gel
• The current output can be a limiting
factor for solar cell designs
• We chose a 7 inch digital picture
frame, which fits this power output
to power with the 2 inch solar cell
design
Acknowledgements:
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Dr Hailung Tsai
Dr Cheng-Hsiang Lin
Material Research Center
Intelligent System Center
References:
1) P. V. Kamat. J. Phys. Chem. C 111, 2834-2860 (2007)
2) A. Luque. Journal of Applied Physics 110, 031301 (2011)
3) V. V. Iyengar, B. K. Nayak, M. C. Gupta. Solar Energy
Materials and Solar Cells 94, 2251-2257 (2010)