Solar cellsAbhishek Gupta(0905232002) Anamika(0905232005) Ashish Kumar Mishra(0905232008) Vinit Kumar Mishra(1005232903)

OverviewSolar cell fundamentalsNovel solar cell structuresThin film solar cellsNext generation solar cell

Appealing CharacteristicsConsumes no fuelNo pollutionWide power-handling capabilitiesHigh power-to-weight ratio

Solar Energy SpectrumPower reaching earth 1.37 KW/m2

Air MassAmount of air mass through which light passAtmosphere can cut solar energy reaching earth by 50% and more

Solar cell Working PrincipleOperating diode in fourth quadrant generates power

OverviewSolar cell fundamentalsNovel solar cell structuresThin film solar cellsNext generation solar cell

Back Surface FieldsMost carriers are generated in thicker p regionElectrons are repelled by p-p+ junction field

Schottky Barrier CellPrinciple similar to p-n junction cellCheap and easy alternative to traditional cellLimitations:Conducting grid on top of metal layerSurface damage due to high temperature in grid-attachment technique

Grooved Junction CellHigher p-n junction areaHigh efficiency ( > 20%)

OverviewSolar cell fundamentalsNovel solar cell structuresThin film solar cellsNext generation solar cell

Thin Film Solar CellsProduced from cheaper polycrystalline materials and glassHigh optical absorption coefficientsBandgap suited to solar spectrum

CdTe/CdS Solar CellCdTe : Bandgap 1.5 eV; Absorption coefficient 10 times that of SiCdS : Bandgap 2.5 eV; Acts as window layerLimitation : Poor contact quality with p-CdTe (~ 0.1 Wcm2)

Inverted Thin Film Cellp-diamond (Bandgap 5.5 eV) as a window layern-CdTe layer as an absorption layer

Efficiency Losses in Solar Cell1 = Thermalization loss 2 and 3 = Junction and contact voltage loss4 = Recombination loss

OverviewSolar cell fundamentalsNovel solar cell structuresThin film solar cellsNext generation solar cell

Tandem CellsCurrent output matched for individual cellsIdeal efficiency for infinite stack is 86.8%GaInP/GaAs/Ge tandem cells (efficiency 40%)

Multiple E-H pairsMany E-H pairs created by incident photon through impact ionization of hot carriersTheoretical efficiency is 85.9%

Multiband CellsIntermediate band formed by impurity levels.Process 3 also assisted by phononsLimiting efficiency is 86.8%

Multiple Quantum WellPrinciple of operation similar to multiband cells

Thermophotonic CellsHeated semiconductor emits narrow bandwidth radiationsDiode with higher temperature has lower voltage

Thermophotovoltaic CellFilter passes radiations of energy equal to bandgap of solar cell materialEmitter radiation matched with spectral sensitivity of cellHigh Illumination Intensity ( ~ 10 kW/m2 )

Thermophotovoltaic Cells Efficiency almost twice of ordinary photocell

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