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Ee 332 spring 2013 solar cellsolar cell efficiency

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Unformatted text preview: ellSolar Cell Efficiency Efficiency EE 332 Spring 2013 Solar Energy Consumptionstill way too low The solar energy consumption is Renewable Energy Consumption in the Nation’s Energy Supply, 2009 Source: U.S. Energy Information Administration, Office of Coal, Nuclear, Electric and Alternate Fuels. EE 332 Spring 2013 Promote the Application of Solar Energy Promote the application of solar energy Cell technologies – market shares in 2008 (Source: Photon International, April 2009) EE 332 Spring 2013 Light Emitting Devices – Basics Light Emitting Devices – Basics • • • Emission of photons by recombination of electrons and holes in direct bandgap materials Photoluminescense: excess electrons and holes required for the radiative recombination are generated by photon absorption Electroluminescense: excess electrons and holes required for the radiative recombination are result of an electrical current www.osram.com Georgia Tech Slide Credit to Dr. Oliver Brandt, Ga Tech EE 332 Spring 2013 ECE 3080 - Dr. Alan Doolittle LED •  Attach the Movie EE 332 Spring 2013 Diode Applications: LED or a Laser Diode LED Material I Light Emission under forward Bias V1=IR R=1000 ohms VA V=9V Diode made from a direct bandgap semiconductor. Quantum well made from smaller bandgap material Electron Current P-type Al0.5Ga0.5As -qVA FP Hole Current Georgia Tech GaAs FN Light N-type Al0.5Ga0.5As Note: These devices may not be a simple p-n type diode, but behave electrically identical to a p-n junction diode. Majority Carriers that are injected to the opposite side of the diode under forward bias become minority carriers and recombine. In a direct bandgap material, this recombination can result in the creation of photons. In a real device, special areas are used to trap electrons and holes to increase the rate at which they recombine. These areas are called quantum wells. ECE 3080 - Dr. Alan Doolittle EE 332 Spring 2013 MQW LED Design Consideration MQW LED Design Considerations Nakamura, S. et al., “High-power InGaN single-quantum-...
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