Enhancement of Quantum Dot-sensitized Solar Cell...
Transcript of Enhancement of Quantum Dot-sensitized Solar Cell...
Dr. Khalil Ebrahim Jasim
Department of Physics
University of Bahrain
Enhancement of Quantum Dot-sensitized Solar Cell
Efficiency with Natural Dye Extract
Introduction
Motivation
Experimental
Results and discussion
Conclusion
Outline
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Solar Park
Jenny Nelson, The Physics of Solar Cells, 2003.
e-
usable photo-voltage (qV)
Energy
e-
n-type
p-type
heat loss
heat loss
hν
h+
Conventional p-n Junction Photovoltaic Cell
Shockley-Queisser Limit
Optimal bandgap for single-junction solar cell
Solar Cells Generations
January 2005 Materials Research Society Bulletin
Nanostructured Solar Cells
3rd Generation Solar Cells: Emerging PV
Quantum Dots Solar CellWhat limits the
efficiency:Photons with lower
energy than the band
gap are not absorbed.
Photons with greater
energy than the band
gap are absorbed but
the excess energy is
lost as heat.
K. E. Jasim, “Dye sensitised solar cells—working principles, challenges and opportunities,” in Solar Cells/Book 2, INTECH, 2011.
Quantum dots, also known as nanocrystals, are a special class of
materials known as semiconductors, which are crystals composed of
periodic groups of II-VI, III-V, or IV-VI materials.
Quantum dots are unique class of
semiconductor because they are
so small, ranging from 2-10 nm
in diameter.
What Is a Quantum Dot?
A PbSe Quantum Dot as seen through a transmission electron microscope (TEM).
Semiconductors such as:
CdS, CdSe, CdTe, CuInS2, Cu2S, PbS, PbSe,
InP, InAs, Ag2S, Bi2S3 and Sb2S3 have been
synthesized as QDs and deposited onto wide
bandgap semiconductors as sensitizers.
Especially CdS, CdSe and PbS have been
used to investigate the operating principles of
QDSCs.
QD Materials
How Can Quantum Dots Improvethe Efficiency?
Quantum dots can generate multiple exciton (electron-hole pairs) after collision with one photon.
Hot Carriers
In bulk semiconductors recombination of hot electron‐holes is very fast and hence Multiple Exciton Generation (MEG) though present is very rare.
Recombination in QDs is
much slower than in bulk
because of confinement
effects.
Conversion of photons into charge carriers without (A)and with (B) carrier multiplication.
Multiple Exciton Generation (MEG)
Richard D. Schaller, Milan Sykora, Jeffrey M. Pietryga, and Victor I. Klimov, NANO LETTERS 2006 Vol. 6, No. 3, 424‐429.
0
1
2
3
4
5
0 5 10 15 20 25 30 35 40 45 50
Ene
rgy
ban
dga
p (
eV
)
Quantum dot radius (nm)
GaN
CdS
CdSe
InAs
InPPbTe
PbS
CTeGaAs
Figuresare from “Quantum Dots Explained.” Evident Technologies. 2008.
Effective Mass Model
Filter or
Monochromato
r
hDifference
amplifier
00
100
Lens
Mirror
Mirror
Shutter
Beam
Splitter
Sample
cell
Reference
cell
PO
P
Photo
detector 1
Photo
detector2
Readout
Filter or
Monochromato
r
Filter or
Monochromato
r
hDifference
amplifier
Difference
amplifier
00
100
Lens
Mirror
Mirror
Shutter
Beam
Splitter
Sample
cell
Reference
cell
PO
P
Photo
detector 1
Photo
detector2
Readout
400 600 800 1000 1200 1400 1600
0
1
2
3
4
5
2.4 nm
3.2 nm 5.0 nmAb
so
rba
nce
(a
.u.)
Wavelength (nm)
Absorbance of PbS Quantum Dots of Different Radii and Dye Extract
400 600 800 1000 1200
0
1
2
3
4
Ab
so
rban
ce (
au
)
Wavelength (nm)
Think Green Biomimicry
A dye monolayer
chemically absorbed on
the semiconductor is the
primary absorber of
sunlight; free charge
carriers are generated by
electron injections from a
dye molecule, excited by
visible radiation
K. E. Jasim, “Dye sensitized solar cells—working principles, challenges and opportunities,” in Solar Cells/Book 2, INTECH, 2011.
© Dyesol
- +
Electron
energy
Eredox
qVmax
SnO2
Glass
TiO2
Nanolayer
Quantum
Dots
Conduction
Band
Valance
Band
Counter
Electrode
Electrolyte
e-e-
e-
e-
e- e-
e-
3I-
I3-
Load
Light
1D(e)
1P(e)
1S(e)
1D(h)
1P(h)
1S(h)
h+
Dye
Molecule
e-
LUMO
h+
HUMO
Graphite
layer
Cell Preparation & Testing
Nanostructured TiO2 Layer
K. E. Jasim, S. Al-Dallal, and A.M. Hassan, “Natural dye-sensitised photovoltaic cell based on nanoporous TiO2”. Int. J. Nanoparticles, Vol. 4, No. 4, pp. 359-368, 2011.
KISS Approach
Keep It Simple & Smart
Approach
I-V Characteristics
0 50 100 150 200 250 300 350
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Mixed QD
2.4 nm
5.0 nm
3.2 nmP
ho
tocu
rren
t (m
A)
Voltage (mV)
I-V characteristics of 2.4 nm PbS QDs
0 50 100 150 200 250 300 3500.0
0.1
0.2
0.3
0.4
0.5
0.6
Without Dye
With DyeP
ho
tocu
rren
t (m
A)
Voltage (mV)
I-V characteristics of 3.2 nm PbS QDs
0 50 100 150 200 250 300 350 400
0.0
0.2
0.4
0.6
0.8
1.0
Without Dye
With Dye
Ph
oto
cu
rren
t (m
A)
Voltage (mV)
0 50 100 150 200 250 300
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Without Dye
With Dye
Ph
oto
cu
rren
t (m
A)
Voltage (mV)
I-V characteristics of 5.0 nm PbS QDs
Measured and calculated parameters for the three assembled QDs sensitized solar cells and
the dye enhanced solar cells using pomegranate as dye sensitizer
3.5 1.6 10.7
Transmittance of the Electrode
500 1000 1500 2000 2500 30000
10
20
30
40
50
60
70
Uncoated electrode
Coated electrode with
annealed TiO2
%T
Wavelength (nm)
Semiconductor Sensitized Solar Cells:
Like DSSCs they are quite cheaper to produce.
Tunability of QD optical properties with size.
In QD‐sensitized solar cell, the production of quantum yield is
greater than one due MEG (inverse Auger effect). Dye molecules
cannot undergo this process.
Dye Extract Enhances Quantum Dot-sensitized Solar Cell Efficiency.
Conclusion
Thank you for your attention