ECE3080-L-11c-Solar Cells

ECE3080-L-11c-Solar Cells - Solar Cells ECE 3080/ECE 3040...

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Solar Cells ECE 3080/ECE 3040 Lecture Dr. Doolittle February 22, 2008 References – PVCDROM by Dr. Honsberg at the University of Delaware www.udel.edu/igert/pvcdrom National Renewable Energy Laboratory www.nrel.gov University Center of Excellence for Photovoltaics www.ece.gatech.edu/research/UCEP Elaissa Trybus – elaissa@ece.gatech.edu
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What is the highest efficiency Solar Cell?
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GT CRC Roof-Mounted PV System λ Largest single PV structure at the time of it’s construction for the 1996 Olympic games λ Produced more than 1 billion watt hrs. of electrical energy that has been fed into the GT power grid PV - Photovoltaic
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Law et. al, Conference Record of the 2006 IEEE 4 th World Conference on Photovoltaic Energy Conversion, pp. 1879. λ GaInP/GaInAs/Ge by Spectrolab (A Boeing Company) achieved 40.7% efficiency in 2007. λ Current devices employed on satellites have efficiencies ~28.3% λ An approximate device structure Highest Efficiency Device
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Energy of a Photon E [eV] = h c= 1.24 λ λ [ µ m] c = 3 × 10 8 [m/s] h = 6.626 × 10 -34 [J·s] λ is the wavelength of light in meters J = 1.602 × 10 -19 [eV] Bandgap [eV] Wavelength [ µ m] Ge 0.67 1.85 Si 1.12 1.107 GaAs 1.42 0.873 GaN 3.4 0.365
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Photovoltaic Effect λ Solar cells are: – p-n junctions – Minority carrier devices – Voltage is not directly applied λ The photocurrent produces a voltage drop across the resistive load, which forward biases the pn junction. R PN - - - - - - + + + h ν + V - I F I total I L E-Field
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Photovoltaic Effect Power = V × I Current Absorption of light Creation of additional EHP Voltage Excitation of electrons Separation by e - field Movement in e- field λ Fundamental absorption is from: annihilation or absorption of photons by the excitation of an electron from the valence band to the conduction band leaves a hole in the valence band λ Ideally, each incident photon with E h ν > E G will create one electron flowing in the external device λ E h ν < E G : semiconductor is transparent to light
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ECE3080-L-11c-Solar Cells - Solar Cells ECE 3080/ECE 3040...

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