microlens array light trapping cdte solar cells for use in concentrator photovoltaics
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Microlens Array Light Trapping CdTe Solar Cells for use in Concentrator Photovoltaics. Student : Patrick Margavio , Mechanical and Aerospace Engineering. Faculty Advisor : Dr. Hailung Tsai, Mechanical and Aerospace Engineering. What is Light Trapping? - PowerPoint PPT PresentationTRANSCRIPT
Microlens Array Light Trapping CdTe Solar Cells for use in Concentrator Photovoltaics
Student: Patrick Margavio, Mechanical and Aerospace Engineering Faculty Advisor: Dr. Hailung Tsai, Mechanical and Aerospace Engineering
Why Solar?• 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
Why Concentrate Solar Energy? There are two basic strategies to compete with fossil fuels
• Make solar inexpensive• Copper indium gallium diselenide, dye sensitized solar• Commercially available single and polycrystalline silicon• Solar houses on campus
• Maximize efficiency• Combine solar cell (like multijunction GaAs) with solar concentrator• Mirrors, Luminescent Solar Concentrators• Solar cell is 75% of cost of systemWhat’s a Microlens Array?
• 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
• 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
• G code used to computer control process is shown
• After laser machining Foturan glass is baked at 5000C and then at 6000C.
• After baking, sample is etched with HF acid
• After etching sample is annealed for another hour
Making the Microlens Array Mold:
What is Light Trapping?• There are two basic ways to trap light within a solar cell
• Reducing the amount of light reflected away from top surface• Examples below scatter incoming light to reduce reflection3
• Preventing light from leaving once it has entered
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
Making the Silicon Microlens Array:• The silicon gel used is Polydimethylsiloxane (PDMS)
• PDMS is combined with a curing agent
• The PDMS mixture is poured over the glass mold
• Sample is placed in a vacuum chamber (right) to remove bubbles from mixing process
• Next PDMS is cured at 700C for one hour in a furnace to solidify
• To left, a microscope image of the silicon film is visible. Below, the glass mold is shown in the silicon gel
Acknowledgements:• 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)
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)
• The current output can be a limiting factor for solar cell designs
• We chose a 7 inch digital picture frame, which fits this power outputto power with the 2 inch solar cell design