Lecture4_EnergyBandDiagramOperationOfSolarCEll

Lecture4_EnergyBandDiagramOperationOfSolarCEll -...

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d t d i th ll ti f lt il Understanding the collection of electrical carriers (separation of electrons and l ) d Ct i Ud t holes) and Connections Used to Distribute Current omojunctions etal miconductor Junctions P N Homojunctions, Metal Semiconductor Junctions, Heterojunctions, and Insulator Semiconductor Junctions Reading: Notes Dr. Alan Doolittle Ga Tech ECE 4833 Some images from Anderson and Anderson text and Dr. Fred Schubert Webpage at RPI
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Basic Collecting Junctions tro and Comparisons Intro and Comparisons Role of the collecting junction : It is the role of the collecting junction to separate the electron and hole pairs and force them to “collect” in spatially different regions of the device, thus creating a voltage and facilitating a current. Dr. Alan Doolittle Ga Tech ECE 4833
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Basic Collecting Junctions tro and Comparisons Intro and Comparisons p n Homojunctions : The main collecting junction used in hotovoltaics “Simple” but proper photovoltaics. “Simple” but proper implementation in PV requires carful attention to details. Other devices are more forgiving than PV Heterojunctions : The main collecting junction for advanced, high performance compound semiconductor devices. Makes more efficient use of the energy spectrum of the sun. Schottky Junctions (Diodes) : Rarely intentionally used in PV due to inherently lower voltage than those above. owever, many metal miconductor Dr. Alan Doolittle Ga Tech ECE 4833 However, many metal semiconductor junctions can only be made as Schottky Diodes.
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Basic Collecting Junction Homojunction Example p n Homojunction Example Dr. Alan Doolittle Ga Tech ECE 4833
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Movement of electrons and holes under Bias (electrical or light) Voltage Bias V bi |V A | V A =0 : No Bias V A <0 : Reverse Bias V A >0 : Forward Bias V bi V bi V bi |V A | Dr. Alan Doolittle Ga Tech ECE 4833
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Movement of electrons and holes under Bias (electrical or light) Light Bias V A =0 : No Bias (no light) V A >0 : Forward Bias due to Light V bi V bi |V A | Dr. Alan Doolittle Ga Tech ECE 4833
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Movement of electrons and holes under Bias (electrical or light) Light Bias V A >0 : Forward Bias due to Light Voltage drives the charge into the external circuit generating power (V x I) V bi Excess charge on either side of the junction creates a Voltage: j g Q=CV (but in this case C is also a nonlinear function of V) Dr. Alan Doolittle Ga Tech ECE 4833
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Movement of electrons and holes under Bias (electrical or light) Light Bias V A >0 : Forward Bias due to Light Voltage drives the charge into the external circuit generating power (V x I) V bi |V A | Dr. Alan Doolittle Ga Tech ECE 4833
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Basic Collecting Junction Homojunction Description p n Homojunction Description Dr. Alan Doolittle Ga Tech ECE 4833
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Our First Device: p n Junction Diode N type material P type material N type material P type material A p n junction diode is made by forming a p type region of material directly next to a n type region. y yp g Dr. Alan Doolittle Ga Tech ECE 4833
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Our First Device: p n Junction Diode N D N A N D x N A
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This note was uploaded on 08/23/2011 for the course ECE 4833 taught by Professor Doolittle during the Spring '10 term at Georgia Institute of Technology.

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Lecture4_EnergyBandDiagramOperationOfSolarCEll -...

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