Dye Sensitized Solar Cells: History, Principle, and Efficiency Parameters

LITERATURE REVIEW
1.1. History of both DSSC’s and photovoltaic
The effect of photovoltaic can also be generalized and defined as the process that converts the
sunlight directly into electricity. It was discovered first in 1839 by a French physicist, Nobel
Laureate and Becquerel when they critically observed the dependency voltage of light through
the electrodes that emerged through electrolyte (Wei, 2010). The first silicon solar cell was
manufactured in 1955 having an ability to convert only 6% (Gourbilleau, Ternon, Maestre, Palais
and Dufour, 2009). The principle of generation of power by dye sensitized solar cell were later
worked on by two Germany scientist by the name Tributsch and Gerischer during 1960’s and
1970’s (Spitler and Parkinson, 2009). The introduction of Nano porous electrodes was done in
1990’s by a Swiss scientist who was also a professor Ecole polytechnic in Switzerland, this
introduction improved the efficiency of conversion of the dye sensitized solar cell to 7%
(Mathew et al, 2014), this technology purely open up more extensive and detailed research.
1.2. The Principle of a working Dye Sensitized Solar Cells
The format of DSSC comprises of a cathode and an anode that contains a layer of oxide in
between them, they are also sensitized by a dye and electrolyte layer. The anode structure is
transparent to enable easier absorption of sunlight by solar cell inner parts. (Kalyanasundaram,
2010). Titanium dioxide mesh of oxide is fixed between the cathode and anode, this
nanoparticles acts as a pathway used by the electrons (Green, 2004). The nanoparticles are
coated with dyes that are able to convert the absorb light or photons into electricity or electrons
(Su and Shen, 2012 ). The Iodide electrolyte helps in filling the space found between
nanoparticles and also is helps in transferring electrons from the cathode to the molecules of the
dye (Tributsch, H., 2009).
 The role of the anode is to send electrons through the connected wires from the solar cell,
the electrons then loops back to the negative electrode (cathode) (Gong, Liang and
Sumathy, 2012)
 The electrolyte and Titanium oxide nanoparticles help in transferring electrons in order
to create electrical current (Gong, Liang and Sumathy, 2012).
 The TiO2 nanoparticles acts as a conductor because they have a special ability of forming
a wide connected network which helps the travelling of electrons (Gong, Liang and
Sumathy, 2012).
 The dye molecules that coats TiO2 nanoparticles when it is hit with light they produce
electrons. The dye color is a core objectivity of determining the type of light to be
absorbed which varies with their wavelength, the variety of light absorbed determines the
amount of energy (Gong, Sumathy, Qiao and Zhou, 2017).
 The is different random travelling of electrons from one TiO2 nanoparticles to other
nanoparticles until the anode is reached (Nazeeruddin, Baranoff and Grätzel, 2011 ).

 The striking of photon on the surface of the dye molecule transfers energy to the dye
molecule. The molecule then enters an exicited state to make it emit electrons, the
electron will then travel to the TiO2 nanoparticles until the anode is reached
(Nazeeruddin, Baranoff and Grätzel, 2011).
 The immersion of dye-coated TiO2 molecules into Iodide electrolyte helps in replacing
the lost electrons by the dye molecules (Taleb et al, 2016).
 The molecule of the Iodide in the electrolyte of Iodide helps in giving up electrons that
are needed by the dye molecules, in this process the Iodide molecules will undergo
oxidation to form new compound called triiodide that are light in weight which makes
them float until it combines with the cathode (Bakhshayesh. and Mohammadi, 2013).
 The missing electron of the triiodide is recovered from the cathode that helps it undergo
reduction and return it back to three Iodide molecules (Wu et al, 2008).
 The emitted electrons from the dye then flows from the anode through the connecting
wire of the solar cell and then returns back through the cathode in the cell (Wu et al,
2008).
 There will be now restoration of electrons that are required by the dye molecules from
the cathode and the process again starts over (Wu et al, 2008).
Figure 1: Operation of a dye sensitized solar cells.

Figure 2: DSSC corposants and reaction summary.
The DSSC photoactive material is the dye which is has the ability to produce electricity upon it
being sensitized by the light
The dye absorbs the photons of the directed light and uses its energy in excitation of electrons
The excited electrons is injected by the dye into TiO2
The Nano crystalline TiO2 conducts away the electrons
The circuit is complete by the chemical electrolyte to enable the electrons to return back into the
dye