Solar cells课件.ppt

Solar_cells课件
Overview
Solar cell fundamentals
Novel solar cell structures
Thin film solar cells
Next generation solSolar_cells课件
Overview
Solar cell fundamentals
Novel solar cell structures
Thin film solar cells
Next generation solar cell
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Appealing Characteristics
Consumes no fuel
No pollution
Wide power-handling capabilities
High power-to-weight ratio
Solar Energy Spectrum
Power reaching earth KW/m2
Air Mass
Amount of air mass through which light pass
Atmosphere can cut solar energy reaching earth by 50% and more
Solar cell – Working Principle
Operating diode in fourth quadrant generates power
Overview
Solar cell fundamentals
Novel solar cell structures
Thin film solar cells
Next generation solar cell
Back Surface Fields
Most carriers are generated in thicker p region
Electrons are repelled by p-p+ junction field
Schottky Barrier Cell
Principle similar to p-n junction cell
Cheap and easy alternative to traditional cell
Limitations:
Conducting grid on top of metal layer
Surface damage due to high temperature in grid-attachment technique
Efficiency Losses in Solar Cell
1 = Thermalization loss
2 and 3 = Junction and contact voltage loss
4 = Recombination loss
Overview
Solar cell fundamentals
Novel solar cell structures
Thin film solar cells
Next generation solar cell
Tandem Cells
Current output matched for individual cells
Ideal efficiency for infinite stack is %
GaInP/GaAs/Ge tandem cells (efficiency 40%)
Multiple E-H pairs
Many E-H pairs created by incident photon through impact ionization of hot carriers
Theoretical efficiency is %
Multiband Cells
Intermediate band formed by impurity levels.
Process 3 also assisted by phonons
Limiting efficiency is %
Multiple Quantum Well
Principle of operation similar to multiband cells
Thermophotonic Cells
Heated semiconductor emits narrow bandwidth radiations
Diode with higher temperature has lower voltage
Thermophotovoltaic Cell
Filter p