Introduction to photovoltaic: from bulk to thin films

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Introduction to photovoltaic from bulk to thin
films
Isodiana CRUPI
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Climate Change
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Climate Change
yesterday today tomorrow
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Climate Change
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Kyoto Protocol
Agreement under which industrialized countries
will reduce their collective emissions of
greenhouse gases by 5.2 compared to the 1990.
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Solar Radiation Map
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Clean, renewable energy
In one minute, the sun provides enough energy to
supply the worlds needs for one year!
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Solar Radiation Spectrum

• AM0 in space
• AM1 sun at its zenith
• AM1.5 q 48

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What are photovoltaics?

• Photovoltaic is a fancy word, which simply means
  turning light (f??) into electricity (volt).
• Since the sun gives lots of light, photovoltaic
  systems are commonly known as solar cells.

The goals of todays PV

• Reduce cost and improve performance of the solar
  cell
• Reduce cost and improve reliability of Balanca of
  Sysyem (BoS)

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A bit of history of photovoltaic
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p-n junction
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Solar cell I-V curve
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Solar cell I-V curve
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Solar cell I-V curve
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Solar cell I-V curve
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Solar cell parameters
Imax
vmax
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The Shockley-Queisser limit
or detailed balance limit refers to the maximum
theoretical efficiency of a solar cell using a
p-n junction

• Main assumptions
• All photons incident on cell captured
• Complete absorption of all photons with E gt Eg
• Complete thermalization occurs
• Lossless transport and collection of charge
  carriers
• Ideal materials only radiative recombination
  (detailed balance )

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Silicon Feedstock

• Semiconductor grade, purity of 99.999.
• Metallurgical grade, typical purity of 98.5.
• Solar grade

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Cost distribution
silicon wafers
modules
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Momo-crystalline Si solar cell

• 24,7

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Poly-crystalline Si solar cell

• 10

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GaAs solar cell
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Thin film p-i-n junction
WD XNWIXP
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Amorphous Silicon

• 12

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Cadmium Telluride solar cell

• 16,5

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Cu(In Ga)Se2

• CIS 15
• CGS 10.2
• CIGS 19.9 (_at_ NREL 2009)

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Multi junctions solar cell
spectrum-splitting effect
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Multi junctions solar cell
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a-Si/a-SiGe/a-SiGe triple junction
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Tunnel junction
ISC ITC ITJ IBC VSC VTC - VTJ VBC
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Multi junctions solar cell
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Improvements in solar cell Efficiency
energy payback time thin-film cell lt energy
payback time bulk cell
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Process sequence