Dye-sensitized solar cells (DSSCs) convert sunlight to electricity via a photosensitizer dye attached to a semiconductor (typically titanium dioxide). When light is absorbed by the dye, electrons are injected into the semiconductor and collected at the anode. The dye is regenerated by accepting electrons from an electrolyte solution, and the process continues. Michael Gratzel invented the DSSC in 1991. DSSCs can be made flexible and are less expensive than silicon solar cells. Ruthenium-based dyes like N719 are most commonly used but research seeks replacements like organic or natural dyes.

1. Dye Sensitised Solar Cells
Saurav Chandra Sarma

2. Outline
•Solar cells and their importance.
•Dye Sensitized Solar Cell(DSSC) and its compo
•Working of DSSC
•Conclusion

3. What is a Solar
Cell?
A solar cell (also called
a photovoltaic cell) is an
electrical device that converts
the energy of light directly
into electricity
Generates an electric
current without being
attached to any voltage
source

4. It exploits a renewable sources of
energy
It is environmental friendly
Solar cells can be used in remote areas
where it is too expensive to extend the
electricity power grid.
Solar cells last a longer time and have
low running costs
Importance of Solar Cells

6. Buried contact
solar cell
Cadmium
telluride solar
cell
Copper indium
gallium selenide
solar cells
Dye-sensitized
solar cell
Gallium
arsenide
germanium
solar cell
Hybrid solar
cell
Different types of Solar Cells

7. Flexible DSSC Module 
 Glass-based DSSC Module

8. Born 11 May 1944 (age 69)
Dorfchemnitz, Sachsen
Residence Switzerland
Nationality Swiss
Fields photochemistry
Institutions École Polytechnique
Fédérale de Lausanne
Known for Dye-sensitized solar cells
Achievements:
Author of over 900 publications, two books and inventor or co-inventor of
over 50 patents
On 9 June 2010, Grätzel received Millennium Technology Prize, for
development of dye-sensitized solar cells.
Michael Gratzel: Father of DSSC

9. •The material of choice has been TiO2 (anatase), although alternative
wide-band-gap oxides such as ZnO and Nb2O5 have also been
investigated.
•Nanoparticles of the oxide are deposited, for example, by screen
printing onto a glass or flexible plastic support.
•The surface is then coated with layers of sensitizer.
What are the constituents of DSSC?

10. The main processes that occur in a DSSC
1. The incident photon is absorbed by Ru complex photosensitizers adsorbed on the
TiO2 surface.
2. The photosensitizers are excited from the ground state (S) to the excited state (S∗). The
excited electrons are injected into the conduction band of the TiO2 electrode. This results in
the oxidation of the photosensitizer (S+).
S + hν → S∗
S∗ → S+ + e− (TiO2)
3. The injected electrons in the conduction band of TiO2 are transported between
TiO2 nanoparticles with diffusion toward the back contact (TCO). And the electrons finally
reach the counter electrode through the circuit.
4. The oxidized photosensitizer (S+) accepts electrons from the I− ion redox mediator leading
to regeneration of the ground state (S), and the I− is oxidized to the oxidized state, I3
−.
S+ + e− → S
5. The oxidized redox mediator, I3
−, diffuses toward the counter electrode and then it is
reduced to I− ions.
I3
− + 2 e− → 3 I−
Mechanism of DSSC

11. Incident photon is absorbed
by Ru complex
Electrons are excited
from ground sate to the
excited state
Excited electrons are injected
into the conduction band of
TiO2
Oxidized photosensitizer
accepts electrons from the
I−
The oxidized redox
mediator, I3
−, diffuses
toward the counter
electrode

12. Dynamics of Electron Injection
The dyes should incorporate
functional group such as , for
e.g, carboxylate, hydroxymate,
or phosphate moieties that
anchor the sensitizer to the
oxide surface.
Metal to Ligand Charge
Transfer(MLCT) occurs which
facilitates the rapid electron
injection from the ligand to the
semiconductor.

13. Absorption spectrum of N719 dye(sensitizer) shows
the transfer of electron from Ru to Ligands before
donation to the conduction band of TiO2
Proof of MLCT transition

14. The most widely used sensitizer for the DSC has been cis
Ru(SCN)2L2(L)2,2′-bipyridyl-4,4′-dicarboxylate), abbreviated as N3

15. Some of the Ruthenium Sensitizers
RuL3(yellow) cis-RuL2(NCS)2(red) RuL′(NCS)3(green)

16. DSSC Performance
Conversion of light to
elecric current by
mesoscopic solar
cells sensitized with
the ruthenium dye N-
719. The IPCE is
plotted as a function
of the excitation
wavelength.
IPCE: Incident Photon to Current conversion Efficiency
The IPCE values exceed 80% in the wavelength range near the
absorption maximum of the sensitizer,which is located around 530 nm

17. Lets look at an animation to
visualise the process better

19. The transport of the electroactive ions is expected to play
a significant role in determining DSSC efficiency
The search for suitable solid materials that can replace
the liquid electrolyte is an additional interesting and
active area of research.
Research on dye sensitizers are mainly focused on
transition metal complexes, but a considerable of work is
now directed towards the optimization of organic
sensitizers and of natural sensitizers extracted from
fruits.
Conclusion

20. References
•Michael Gratzel, Inorganic Chemistry, Vol. 44, No. 20,
2005 6849
•Gratzel, M. Nature 2001, 414, 338.