350
S. S. B. Gunasekera et al.
and operational stability due to leakage of toxic organic solvent and increase in internal resistance due to evaporation of volatile components such as iodine. Hence as
an alternative the use of ionic liquid, quasi-solid state and solid state electrolytes
have been investigated. The use of room temperature ionic liquids such as 1,3dialkylimidazolium, 1,2,3-trialkylimidazolium and N-alkylpyridinium (Gorlov et al.
2007) are investigated and it had been possible to achieve significant efficiency with
ionic electrolytes of eutectic salts (Bai et al. 2008).
The CE is responsible for the electron transfer from the external circuit back to the
redox mediator thus completing the circuit. A CE material needs to possess excellent catalytic activity for redox electrolyte reduction, low resistance, high chemical
stability and low production cost (Rahman et al. 2016). A typical CE is made out
of a transparent conductive oxide glass on which a catalyst is fabricated (Thomas
et al. 2014). The applicability of a wide variety of CE materials in DSCs has been
extensively investigated in the recent years, this is been discussed in detail under
Sect. 17.1.2 as this is the main focus of the chapter.
The preliminary characterization method for a DSC is current density-voltage
(J-V) curves. The overall performance of a DSC can be evaluated in terms of cell
efficiency (ï) and fill factor (FF) that can be derived from a typical J-V curve.
ï is described as the quantum yield of photogenerated electron for the incident
photonflux. The FF is another parameter that has an influence on the cell efficiency
which relies on internal resistance and electron transfer. In addition to these two
parameters the short circuit current density (J sc ) and open-circuit voltage V oc ) can
also be derived from J-V curves (Gong et al. 2012).
The main focus of this chapter is the applicability of conducting polymers as
promising substitute material for Pt CE in DSCs with a brief introduction on DSCs
and their operational principle. The advantages and the drawbacks associated with the
usage of the typical Pt CE is discussed followed by a description of other promising
candidates as a substitute for the Pt CE. Then the use of conducting polymers as a CE
material is reviewed focussing on three of the most promising conducting polymers
and polymer hybrid composites. These conducting polymers and polymer hybrid
composites are discussed in detail focussing on their synthetic methods, fabrication
processes and their respective photovoltaic performances.
17.1.2 CE Materials
Pt has been utilized as the preferred CE material with regard to its high conductivity,
high electrocatalytic activity towards reduction of I
−
3 to I
− which is the typical redox
mediator in DSCs and high light to electric energy conversion efficiency. A DSC
with an exceptionally high efficiency of 12.3% was reported with the use of thermally
decomposed platinum (Yella et al. 2011). The applicability of a variety of Pt materials
as CE in DSCs has been investigated. Pt nano particles synthesized by means of
decomposition of chloroplatinic acid thermally and electrochemical reduction of
hexachloro platinic acid (Fu et al. 2012) was found to be a promising CE material
S. S. B. Gunasekera et al.
and operational stability due to leakage of toxic organic solvent and increase in internal resistance due to evaporation of volatile components such as iodine. Hence as
an alternative the use of ionic liquid, quasi-solid state and solid state electrolytes
have been investigated. The use of room temperature ionic liquids such as 1,3dialkylimidazolium, 1,2,3-trialkylimidazolium and N-alkylpyridinium (Gorlov et al.
2007) are investigated and it had been possible to achieve significant efficiency with
ionic electrolytes of eutectic salts (Bai et al. 2008).
The CE is responsible for the electron transfer from the external circuit back to the
redox mediator thus completing the circuit. A CE material needs to possess excellent catalytic activity for redox electrolyte reduction, low resistance, high chemical
stability and low production cost (Rahman et al. 2016). A typical CE is made out
of a transparent conductive oxide glass on which a catalyst is fabricated (Thomas
et al. 2014). The applicability of a wide variety of CE materials in DSCs has been
extensively investigated in the recent years, this is been discussed in detail under
Sect. 17.1.2 as this is the main focus of the chapter.
The preliminary characterization method for a DSC is current density-voltage
(J-V) curves. The overall performance of a DSC can be evaluated in terms of cell
efficiency (ï) and fill factor (FF) that can be derived from a typical J-V curve.
ï is described as the quantum yield of photogenerated electron for the incident
photonflux. The FF is another parameter that has an influence on the cell efficiency
which relies on internal resistance and electron transfer. In addition to these two
parameters the short circuit current density (J sc ) and open-circuit voltage V oc ) can
also be derived from J-V curves (Gong et al. 2012).
The main focus of this chapter is the applicability of conducting polymers as
promising substitute material for Pt CE in DSCs with a brief introduction on DSCs
and their operational principle. The advantages and the drawbacks associated with the
usage of the typical Pt CE is discussed followed by a description of other promising
candidates as a substitute for the Pt CE. Then the use of conducting polymers as a CE
material is reviewed focussing on three of the most promising conducting polymers
and polymer hybrid composites. These conducting polymers and polymer hybrid
composites are discussed in detail focussing on their synthetic methods, fabrication
processes and their respective photovoltaic performances.
17.1.2 CE Materials
Pt has been utilized as the preferred CE material with regard to its high conductivity,
high electrocatalytic activity towards reduction of I
−
3 to I
− which is the typical redox
mediator in DSCs and high light to electric energy conversion efficiency. A DSC
with an exceptionally high efficiency of 12.3% was reported with the use of thermally
decomposed platinum (Yella et al. 2011). The applicability of a variety of Pt materials
as CE in DSCs has been investigated. Pt nano particles synthesized by means of
decomposition of chloroplatinic acid thermally and electrochemical reduction of
hexachloro platinic acid (Fu et al. 2012) was found to be a promising CE material