Dye Sensitized solar cells

1. DYE SENSITIZED SOLAR
CELLS
Dileep V Raj
Mtech Renewable Energy Technologies
Amrita Vishwa Vidyapeetham,Coimbatore
1

2. What’s Solar Energy?
• Solar energy Originates with the thermonuclear fusion
reactions occurring in the sun.
• Represents the entire electromagnetic radiation (visible light,
infrared, ultraviolet, x-rays, and radio waves).
• This energy consists of radiant light and heat energy from
the sun.
• Out of all energy emitted by sun only a small fraction of
energy is absorbed by the earth.
• Just this tiny fraction of the sun’s energy is enough to meet
all our power needs.
2

3. • Energy produced
by the sun
• Clean, renewable
source of energy
• Harnessed by solar
collection methods
such as solar cells
• Converted into
usable energy such
as electricity
Photovoltaic (solar)
panel
Set of solar panels
3

4. What is a Photovoltaic Cell
• A device that can convert sunlight directly in
electricity.
• Traditional types are based on two types of silicon
sandwiched together (n-type and p-type).
• Based on using photons to separate charges:
electron-hole pairs
• Many new types are in research/production stage.
4

5. Recap : Photo means light in Greek and Volt is the name of a
pioneer in the study of electricity Alessandro Volta
Solar cell: Solar cell is a photovoltaic device that converts
the light energy into electrical energy based on
the principles of photovoltaic effect
Albert Einstein was awarded the 1921 Nobel Prize in physics
for his research on the photoelectric effect—a phenomenon
central to the generation of electricity through solar cells.
5

6. Solar Panel Use Today
• Large companies like
Google, Walmart, and
Microsoft use solar
energy to partially power
some of their facilities
Solar panels on Microsoft building
Solar panels being tested
on Walmart store
6

7. • Renewable energy sources such as solar energy are
considered as a feasible alternative because
“More energy from sunlight strikes Earth in 1 hour than all
of the energy consumed by humans in an entire
year.”(Lewis, 2007).
• The use of natural dye extracts provides natural, non toxic
and low cost dye sources with high absorbance level of
UV, visible and near IR.
• Examples of such dye sources are Bahraini Henna
(Lawsonia inermis L.) and Bahraini raspberries (Rubus spp.).
7

8. Disadvantages of Conventional Solar
cells
o Inefficient and costly equipment
o Environmental Impact of PV Cell Production
o Initial cost is very high
o Requires expert hand and equipment in
manufacture
8

9. Semiconductor Solar
Cells
DSSC
Transparency Opaque Transparent
Environment(Material&
Process)
Normal Great
Power Generation cost High Low
Power Generation
efficiency
High Normal
Color Limited Various
9

10. What is a DSSC?
A dye sensitized solar cell is a new kind of
relatively low cost solar cell with great
potential as its materials are considerably
cheaper and it is simple to make.
10

11. Past
• Michael Grätzel and Brian O’Regan invented “Dye-
sensitized solar cells”, also called “Grätzel cells”, in
2005.
• The first cells were only capable of using light at the
Ultraviolet and Blue end of the spectrum.
• By the turn of the century, advances in technology
were able to broaden the frequencies in which these
cells were able to respond.
• The most efficient of the dyes were simply known as
“Black dyes” due to their very dark colors.
11

12. So What Does this Mean for Solar Cells?
• In dye-sensitized solar cells…
– Talk about highest occupied
molecular orbital (HOMO) and
lowest unoccupied molecular
orbital (LUMO)
• In single-crystal silicon solar
cells…
– Talk about “conduction
band” (excited states) and
“valence band” (ground
states)
12

13. How does a DSSC function?
A DSSC functions due to the interactions
between the cell's anode and the cathode,
and the nanoparticles of titanium oxide,
coated with light sensitive dye and
surrounded by electrolyte.
13

14. Components Of DSSC
• Transparent conducting and counter conducting
electrodes
• The nanostructured wide band gap
semiconducting layer
• The dye molecules (sensitizer)
• The electrolyte.
14

15. Dye Sensitized Solar Cells - Working Principles,
Challenges and Opportunities Khalil Ebrahim Jasim Department of Physics, University of Bahrain Kingdom of Bahrain
Schematic of the structure of the dye sensitized solar cell.
15

16. 16

17. 1. Transparent substrate for both the conducting
electrode and counter electrode
• Clear glass substrates are commonly used as substrate because of
their relative low cost, availability and high optical transparency in
the visible and near infrared regions of the electromagnetic
spectrum.
• TCFs for photovoltaic applications have been fabricated from both
inorganic and organic materials.
• Inorganic films typically are made up of a layer of transparent
conducting oxide (TCO),generally in the form of indium tin oxide
(ITO), fluorine doped tin oxide (FTO), and doped zinc oxide.
17

18. 2.Nanostructured photoelectrode
• In the old generations of photo electro chemical solar
cells (PSC) photo electrodes were made from bulky
semiconductor materials such as Si, GaAs or CdS.
• However, these kinds of photo electrodes when
exposed to light they undergo photo corrosion that
results in poor stability of the photoelctrochemical cell.
• The use of sensitized wide bandgap semiconductors
such as TiO2, or ZnO resulted in high chemical stability
of the cell due to their resistance to photo corrosion.
18

19. • The problem with bulky single or poly-crystalline
wide band gap is the low light to current
conversion efficiency mainly due to inadequate
adsorption of sensitizer because of limited surface
area of the electrode.
• One approach to enhance light-harvesting
efficiency (LHE) and hence the light to current
conversion efficiency is to increase surface area (the
roughness factor) of the sensitized photo electrode.
19

20. • One of the important factors that affect the cell's efficiency is
the thickness of the nanostructured TiO2 layer which must be
less than 20 nm to ensure that the diffusion length of the
photoelectrons is greater than that of the nanocrystalline TiO2
layer.
• TiO2 is the most commonly used nanocrystalline semiconductor
oxide electrode in the DSSC as an electron acceptor to support
a molecular or quantum dot QD sensitizer is TiO2 (Gratzel,
2003).
• Other wide band gap semiconductor oxides is becoming
common is the zinc oxide ZnO. ZnO possesses a band gap of
3.37 eV and a large excitation binding energy of 60 meV.
20

21. 3.Photosensitizer
• Dye molecules of proper molecular structure are used to
sensitized wide bandgap nanostructured photoelectrode.
• Upon absorption of photon, a dye molecule adsorbed to
the surface of say nanostructured TiO2 gets oxidized and
the excited electron is injected into the nanostructured
TiO2.
• Sensitizations of natural dye extracts such as shiso leaf
pigments, Black rice, Fruit of calafate, Rosella ,Natural
anthocyanins ,Henna and wormwood have been
investigated and photovoltaic action of the tested cells
reveals some opportunities. 21

22. Photosensitizer
Fig. (a) Ruthenium based red or "N3" dye adsorbed onto a titanium dioxide
surface (from Martinson et al., 2008), and
(b) Proposed structure of the cyanin dye adsorbed to one of the titanium metal
centers on the titanium dioxide surface (From Smestad, 1988).
N3 dye it has been an outstanding solar light absorber and charge-transfer
sensitizer.
The red dye or N3 dye is capable of absorbing photons of wavelength ranging
from 400 nm to 900 nm. 22

23. Dye-sensitizers
‘Increasing the Efficiency of Solar Cells by Combining Silicon- and Dye Sensitized Devices’ B. Ohms, A. Kleine and U. Hilleringmann International
Conference on Renewable Energies and Power Quality (ICREPQ’12) Santiago de Compostela (Spain), 28th to 30th March, 2012
23

24. Natural Dye Performances
Dye-Sensitized Solar Cells: A Successful Combination of Materials : Claudia Longo and Marco-A. De Paoli* Instituto de Química, Universidade Estadual
de Campinas, CP 6154, 13084-971 Campinas - SP, Brazil
Measured absorbance of some extracted natural dyes in methanol as solvent.
24

25. Redox electrolyte
• Electrolyte containing I-/I3 redox ions is used in DSSC to regenerate the
oxidized dye molecules
• This will complete the electric circuit by mediating electrons between the
nanostructured electrode and counter electrode.
• Cell performance is greatly affected by ion conductivity in the electrolyte
which is directly affected by the viscosity of the solvent.
• NaI, LiI and R4NI (tetraalkylammonium iodide) are well known examples
of mixture of iodide usually dissolved in nonprotonic solvents such as
acetonitrile, propylene carbonate and propionitrile to make electrolyte.
• The redoxing electrolyte needs to be chosen such that the reduction of
I3
ions by injection of electrons is fast and efficient
Dye-Sensitized Solar Cells: A Successful Combination of Materials Claudia Longo and Marco-A. De Paoli* Instituto de Química,
Universidade Estadual de Campinas, CP 6154, 13084-971 Campinas - SP, Brazil
25

26. How Does DSSC Work?
26

27. TiO2 Dye Electrolyte Cathode
Wide band-gap
semiconductor
27

28. -0.5
0
0.5
TiO2
1.0
S*
S°/S+
Dye Electrolyte
OxRed
Cathode
Electron energy
(eV vs. NHE)
-1.0
e-
Wide band-gap
semiconductor
28

29. 1. Light absorption-0.5
0
0.5
TiO2
1.0
S*
S°/S+
hν
Dye Electrolyte
OxRed
Cathode
1
Electron energy
(eV vs. NHE)
-1.0
e-
Wide band-gap
semiconductor
h+
29

30. 1. Light absorption
2. Injection to
semiconductor
3. Percolation
-0.5
0
0.5
TiO2
1.0
S*
S°/S+
hν
Dye Electrolyte
OxRed
Cathode
1
2
3
Electron energy
(eV vs. NHE)
-1.0
e-
Wide band-gap
semiconductor
h+
30

31. 1. Light absorption
2. Injection to
semiconductor
3. Percolation
4. Regeneration of
oxidized dye
-0.5
0
0.5
TiO2
1.0
S*
S°/S+
hν
Dye Electrolyte
OxRed
Cathode
1
2
3
4
Electron energy
(eV vs. NHE)
-1.0
Wide band-gap
semiconductor
e-
h+
31

32. 1. Light absorption
2. Injection to
semiconductor
3. Percolation
4. Regeneration of
oxidized dye
5. Regeneration of
oxidized species
-0.5
0
0.5
TiO2
1.0
S*
S°/S+
hν
Dye Electrolyte
OxRed
Cathode
LOAD
e-
External circuit
1
2
3
4
Electron energy
(eV vs. NHE)
-1.0
Wide band-gap
semiconductor
h+
5
h+
e-
32

33. Maximum Voltage in DSSCs
-0.5
0
0.5
TiO2
1.0
S*
S°/S+
Dye Electrolyte
OxRed
Maximum
Voltage
Cathode
LOAD
e-
External circuit
Electron energy
(eV vs. NHE)
-1.0
e-
Wide band-gap
semiconductor
The voltage is
determined
mainly by the
titania and
redox couple
in the
electrolyte.
h+
33

34. Gratzel, M. (2005). Solar Energy Conversion by Dye-Sensitized Photovoltaic Cells. Inorg. Chem., Vol. 44, pp. 6841-6851.
34

35. Illustration of operation principle of dye sensitized solar cell
35

36. Summary of Dye Sensitized Solar
Cell
36

37. DSSC Preparation
37

38. Image Source : www.thesolarpark.co.uk
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57. Commercialization of DSSC
57

58. COOHHOOC
COOH COOH
HOOC
COOH
HOOC
58

59. Applications Of DSSC
• Because of the physical nature of the dye sensitized solar cells, inexpensive,
environment friendly materials, processing, and realization of various colors,
power window and shingles are prospective applications in building integrated
photovoltaics
• The availability of lightweight flexible dye sensitized cells or modules are
attractive for applications in room or outdoor light powered calculators,
gadgets, and mobiles.
• Flexible dye sensitized solar modules opens opportunities for integrating them
with many portable devices, baggage, gears, or outfits.
• In power generation, dye sensitized modules with efficiency of 10% are
attractive choice to replace the common crystalline Si-based modules.
59

60. Applications of DSSC
(a) 200 m2 of DSSC panels installed in Newcastle (Australia)– the first
commercial DSSC module
60

61. (c) flexible DSSC-based solar module developed by Dyesol (http://www.dyesol.com)
(d) jacket commercialized by G24i (http://www.g24i.com).
D
61

62. Source:http://www.tiberlab.com/dsc-dye-solar-cell.html
62

63. Source:http://www.tiberlab.com/dsc-dye-solar-cell.html
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65. Aesthetic Advantages of DSSCversus
conventional Solar Cells
• Dyes determine the
color of the device.
• Can be transparent
• Can be flexible
• Easy to make
65

66. 66

67. Solar Powered Solar Panel Sun Glasses
The SIG, or “Self-Energy Converting Sunglasses” are quite simple. The lenses of the glasses have
dye solar cells, collecting energy and making it able to power your small devices through the power jack
at the back of the frame. “Infinite Energy: SIG”
Courtesy:SonyCorp.
67

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69. The DSC vs. Conventional Silicon PV
TiO2
Dye
Electrolyte
Cathode
+
̶ n-type
Silicon
p-type
Silicon
+ ̶
+ ̶
+ ̶
+ ̶
• Charge carriers (excited
electrons) are produced
throughout the semiconductor
• Semiconductor considerations:
• Precise doping
• high purity
• high crystalinity
• Light absorption and charge
transport are decoupled
• Relaxed constraints on individual
components (each can be
separately tuned)
• Only monolayer of dye on TiO2
69

70. Solar Cell Efficiencies
Silicon Solar Cell Efficiencies:
Theoretical Maximum: 26%
Best in Lab: 25% (Green, UNSW)
Modules: 15-22%
Thin Film Solar Cell Efficiencies:
Theoretical Maximum: >22%
Best in Lab: 20% (Noufi, NREL)
Modules: 9-12%
Dye-Sensitized Solar Cell Efficiencies:
Theoretical Maximum: 14-20%
Best in Lab: 12% (Grätzel, EPFL)
Modules: 6-9%
70

71. Conclusions
• In short, compared to Si based solar cells dye sensitized solar
cells are of
– low cost and ease of production,
– their performance increases with temperature,
– possessing bifacial configuration - advantage for diffuse light,
have transparency for power windows, color can be varied by
selection of the dye, invisible PV-cells based on near-IR sensitizers
are feasible, and they are outperforms amorphous Si.
• Moreover, DSSC shows higher conversion efficiency than
polycrystalline Si in diffuse light or cloudy conditions.
• It is believed that nanocrystalline photovoltaic devices are
becoming viable contender for large scale future solar
energy converters.
• The search for green sources or generators of energy is
considered one of the priorities in today's societies and
occupies many policy makers' agendas.
71

72. Reference
• Gratzel, M. (2005). Solar Energy Conversion by Dye-Sensitized Photovoltaic Cells. Inorg.
Chem., Vol. 44, pp. 6841-6851.
• Lewis, N. S. (2007). Toward Cost-Effective Solar Energy Use. Science, Vol 315, pp. 798-801.
• Meyer, G. J. Inorg. Chem. 2005, 44, 6852.
• Mallouk, T. E.; Hoertz, P. G. Inorg. Chem. 2005, 44, 6828.
• Nakade, S.; Kubo, W.; Saito, Y.; Kanzaki, T.; Kitamura, T.; Wada, Y.; Yanagida, S. J. Phys.
Chem. B 2003, 107.
• Plass, R.; Pelet, S.; Kruger, J.; Gratzel, M.; Bach, U. J. Phys. Chem. B 2002, 106, 7578.
• Nozik, A. J. Quatum dot solar cells. Next Gener. Photovoltaics 2004, 196.
• Liska er al. 2006, 88, 203103. Marcus, R. A. 1992, Nobel Lecture.
• Bernards, D. A.; Samuel, F. T.; Hector, D. A.; George, G. M. Science, 2006, 313, 1416.
• Amao, Y. & Komori, T. (2004).
• Bio-photovoltaic conversion device using chlorine-e6 derived from chlorophyll from Spirulina
adsorbed on a nanocrystalline TiO2 film electrode. Biosensors Bioelectronics, Vol. 19, Issue 8,
pp. 843-847.
• Harding, H.E.; Hoke, E.T.; Armistrong, P.B.; Yum, J.; Comte, P.; Torres, T.; Frechet, J.M.J.;
Nazeeruddin, M.K.; Gratzel, M. & McGehee, M.D. (2009). Increased light harvesting in dye-
sensitized solar cells with energy relay dyes. Nature Photonics, Vol. 3, pp. 406-411. 72