Dye sensitized solar cells are combination of inorganic semiconductor and organic dyes.

1. Dye Sensitized Solar Cells
Organic optoelectronics| Ashish Singh| B10007

2. Introduction

Low cost solar cells

Invented by Brian o’ Regan and Michael Gratzel at UC Berkley

Conversion efficiency lower then other thin film cells.

Price/performance ratio is better.

Manufactured through Roll printing technique.

3. Dye Sensitized Solar cells

5. Components
The DSSC device consists of 4 components:
Semiconducting electrode

n-type TiO2 and p-type NiO
Dye-sensitizer

Light harvesting and electronic transition
Redox mediator

I- / I3- or CoII / CoIII complexes
Counter electrode

Carbon or Pt

6. Working Principle

Dye Sensitizers absorb the Sunlight, which results in electron
injection into conduction band of Oxide (charge separation takes
place at interface of oxide and dye).

The dye molecules are quite small (nanometer sized), so in order to
capture a reasonable amount of the incoming light the layer of dye
molecules needs to be made fairly thick, much thicker than the
molecules themselves.

8. Working Principle

Original state of Dye is subsequently restored by electron donation
from the electrolyte(Redox iodide/Triodide).

Iodide is regenerated in turn by the reduction of triiodide at the
counter electrode the circuit being completed via electron migration
through the external load.

I3

3I
-
2e
-
3I
-
I3
2e
-
| Redox regeneration at the counter-electrode (oxidation).
|Dye regeneration reaction (reduction).

10. Working Principle

The voltage generated under illumination corresponds to the
difference between the Fermi level of the electron in the solid and the
redox potential of the electrolyte.

Overall the device generates electric power from light without
suffering any permanent chemical transformation

11. Energy Level Diagram

12. TiO2

Low cost

Widely available

Biocompatible material

Non toxic

13. Dye Sensitizers

Absorb all light below a threshold wavelength of about 920 nm.

Contain attachment such as Carboxylate or Phosphonate group for
better attachment with semiconductor oxide.

Quantum yield of unity for injection of electrons in Semiconductor
oxide.

14. Dye Sensitizers

Energy level of the excited state should be well matched to the lower
bound of the conduction band of the oxide to minimize energetic
losses during the electron transfer reaction.

Stable enough to sustain about 10^8 turnover cycles corresponding to
about 20 years of exposure to natural light.

15. Dye-sensitizers

16. Efficiency

Electrical power generated =Isc * Voc

Voc ~ 0.7 (greater then normal Silicon cells)
 Isc
for DSSC ~ 20 mA/cm2 an
Silcon cells ~ 35 mA/cm2
Peak conversion Efficiency achieved ~ 11 %
Max . Peak conversion Efficiency ~ 15 %

17. Disadvantages

Liquid electrolytes are corrosive in nature (iodide/Triiodide couple).

Temperature instability of Liquid electrolytes (freeze in low temp. and
expansion high temp.)

Health hazard of Electrolytes.

18. Solid state Dye Sensitized Solar cells

Solid hole conductor instead of liquid Electrolytes.

The charge transfer material currently used is a spirobifluorene

19. Solid State Dye Sensitized Cells

Hole transfer occurs directly from the oxidized dye to the HOMO level
of the hole conductor, which then transports the charge to the
(typically silver) counter electrode.

Dye regeneration occurs over a period of tens to hundreds of
picoseconds — several orders of magnitude faster than regeneration
with the I - /I 3 couple.

20. Conclusion

DSSCs show the most promising future due to their independence, environmentally
friendly, low maintenance, and low cost .

A solar energy system can be installed in any location without a connection to a power
grid.

The initial investment is expensive. Once the use of electricity reaches to a certain point,
the solar energy is free.

After installation, there is no recurring cost and it can be used for a long time.

21. Bibliography

Grätzel, M. (2003). Dye-sensitized solar cells. Journal of
Photochemistry and Photobiology , 145-153.

hardin, B. e., snaith, h. J., & McGehee, M. D. (2012). the renaissance
of dye-sensitized solar cells. The nature photonics , 162-171.

Nagata, T., & Murakami, H. (2009). Development of Dye-sensitized
Solar Cells. ULVAC Technical Journal , 70E.

Dye Sensitized solar cells. (n.d.). Retrieved from Wikipedia.org:
http://en.wikipedia.org/wiki/Dye-sensitized_solar_cell

22. Thank You !!