quantum yield (Φ) of a radiation-induced process is the number of times a specific event occurs per photon absorbed by the system.
Dye sensitized solar cells
Dye Sensitized Solar Cells
Organic optoelectronics| Ashish Singh| B10007
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.
The DSSC device consists of 4 components:
n-type TiO2 and p-type NiO
Light harvesting and electronic transition
I- / I3- or CoII / CoIII complexes
Carbon or Pt
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
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.
| Redox regeneration at the counter-electrode (oxidation).
|Dye regeneration reaction (reduction).
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
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
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.
Electrical power generated =Isc * Voc
Voc ~ 0.7 (greater then normal Silicon cells)
for DSSC ~ 20 mA/cm2 an
Silcon cells ~ 35 mA/cm2
Peak conversion Efficiency achieved ~ 11 %
Max . Peak conversion Efficiency ~ 15 %
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.
Solid state Dye Sensitized Solar cells
Solid hole conductor instead of liquid Electrolytes.
The charge transfer material currently used is a spirobifluorene
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.
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
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.
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: