Download - Intermediate Band Quantum Dot Solar Cell
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PRESENTATION
ON
INTERMEDIATE BAND QUANTUM DOT SOLAR CELL
S. K. Chaudhary Educational Trust’s
Shankara Institute of Technology Kukas, Jaipur (Rajasthan)
Presented by: VINEET KUMAR Electronics & communication Engg. B.Tech IV Year(VIIIth Sem)
Presented to: Mr. Rajesh Kanwadia Ms. Shweta Agarwal (Sr. Lecturer, Seminar Incharge)
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CONTENTS Photovoltaic Conventional solar cell
Introduction Working Limitations
Energy bands in solids Intermediate band solar cell Quantum dot Intermediate band quantum dot solar
cell Introduction Construction Working Advantages Applications Limitations
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Introduction to Photovoltaic
Generations of voltage
from photons
Light energy ( photons)
are converted into
electrical energy
( voltage).
This conversion is called
“ photovoltaic effect”.
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Photovoltaic Generations
First generation: silicon
wafer-based solar cells
Second generation: thin-
film deposits of semiconductors
Third generation: photo-
electrochemical cells
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Solar Cell
The solar cell (or photovoltaic cell) is a device that converts light energy into electrical energy.
Fundamentally, the device needs to fulfill only two functions:
1. Photo-generation of charge carriers (electrons and holes) in a light-absorbing material.
2. Separation of the charge carriers to a conductive contact that will transmit the electricity.
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Intermediate band solar cell
The intermediate band (IB) is an electronic band located within the semiconductor band gap, separated from the conduction and the valence band by a null density of states.
Intermediate band solar cells (IBSCs) are photovoltaic devices.
Used to exploit the energy of below band gap energy photons.
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ASSUMPTIONS
Only radiation recombination
One electron-hole pair per photon
Constant quasi-Fermi levels
No high energy photons in low energy processes
Maximum concentration of solar radiation
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Intermediate band Requirements
Higher photocurrent Higher efficiency arising from
absorption of 2 sub-band gap photons to create one electron-hole pair.
High voltage V=(EFCB - EFVB)/q V~Eg for main semiconductor
Essential for operation 3 quasi-Fermi levels
IB “disconnected” from emitters Need IB half-filled with electrons Non-overlapping absorption coefficients
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How can we introduce these intermediate
energy levels in the band gap?
Answer “Introduce Quantum
Dots”
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Quantum Dot
A quantum dot is a portion of matter (e.g., semiconductor) whose excitons are confined in all three spatial dimensions.
Quantum dots have properties combined between
Those of bulk semiconductors
Those of atoms
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Physical structure
The structure is as follow :
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Quantum Dot : Types
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Operational principles of IBSC
Incoming photons to base layer can cause three different transitions between valance band (VB), conduction band (CB) and IB depending on their energy:
VB→CB, if the photon energy is greater then ECV.
VB→IB, if the photon energy is greater then EVI
IB→CB, if the photon energy is greater then ECI.
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Salient characteristics of QDs for IBSC
Dot sized shape,
composition
Dot spacing
Dot regularity
Materials
Doping
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ADVANTAGES
Higher Efficiency. Balance between
the two factors
(I) Cost
(II) Efficiency
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APPLICATIONS
Photovoltaic devices: solar cells
Light emitting diodes: LEDs
Quantum computation
Flat-panel displays
Memory elements
Photodetectors
Lasers
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What limits performance of these QD IBSC?
Low open-circuit voltage
Low currents
Cost
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Conclusions
QD SL cells show photo responses extended to longer wavelengths than GaAs control cells, demonstrating current generation from the absorption of sub-band gap photons.
IBSC theoretically offers a way to significantly increase cell efficiency compared to that of a single-junction solar cell.
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Queries