1. A
PRESENTATION
ON
“INTERMEDIATE BAND QUANTUM DOT SOLAR CELL”
Submitted by:-
ABHINAY KUMAR
4th Year,EIC
2. 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
3. Generations of voltage from
photons
Light energy ( photons) are
converted into electrical
energy
( voltage).
This conversion is called
“ photovoltaic effect”.
4. First generation: silicon wafer-
based solar cells
Second generation: thin-film
deposits of semiconductors
Third generation: photo-
electrochemical cells
Fourth generation: composite
photovoltaic technology
5. 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.
8. 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.
9. Higher photocurrent
Higher efficiency arising from absorption of
2 sub-band gap photons to create one
electron-hole pair.
High voltage
V=(EF,CB- EF,VB)/q
V~Eg for main semiconductor
Essentials for operation
3 quasi-Fermi levels
IB “disconnected” from emitters
Need IB half-filled with electrons
Non-overlapping absorption coefficients
12. A quantum dot is a nano meter sized
particle of a low band gap material
surrounded by a material with larger
band gap.
“Artificial atom” with energy levels
depending on the dot size and on the
band gap difference.
If many quantum dots are placed closed
to each other in a lattice one or more
intermediate bands can be formed and a
new semiconductor with tailored
properties has been made.
13. 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
16. Diluted II-VI oxide semiconductors
e.g., Zn1-yMnyOxTe1-x alloys
Transition-metal impurities in
semiconductors e.g., Ga4P3M and
GaxPyM alloys, where M is a
transition metal such as Ti
Quantum dots, e.g., InGaAs/AlGaAs
20. Weak absorption of sub-band gap photons
Low open-circuit voltage
Low currents
Cost
21. QD SL cells show photo responses extended to
longer wavelengths than GaAs control cells,
demonstrating current generation from the
absorption of sub-bandgap photons.
IBSC theoretically offers a way to significantly
increase cell efficiency compared to that of a
single-junction solar cell.
22. Much more work needs to be done before IBSC
can
make a major contribution to the PV market.
“ Miles To Go Before I sleep”