366
S. S. B. Gunasekera et al.
17.3 Summary
The CE is a vital component in DSCs which is responsible for the transfer of electrons
from the external circuit back to the redox mediator and regeneration of redox couple.
The CE electrode typically comprises of a transparent conductive oxide glass on
which a catalyst is fabricated. The applicability of a wide variety of CE materials
has been investigated out of which Pt has been utilized as the preferred CE material
due to its high conductivity and high electrocatalytic activity towards I
−
3 /I
− . The
applicability of Pt as a CE is limited due to its high cost and susceptibility to undergo
corrosion. Hence the use of substitute materials in place of Pt as the CE; such as carbon
based materials, metal organic frameworks, conducting polymers and polymer hybrid
composites have been extensively investigated.
Conducting polymers are considered as promising CE material due to their high
conductivity, high electrocatalytic activity and good stability. Furthermore their
applicability as CE materials is favoured due to cost effectiveness and feasibility
of synthesis. Various conducting polymers such as PANI, PPy, PEDOT and polymer
hybrid composites have been extensively investigated as cost effective CE materials in Pt free DSCs. PANI based CE material is a promising prospect in DSCs
due to appreciable photovoltaic performances and cost effectiveness. PANI reveals
favourable characteristics such as low cost, high electrochemical activity, high environmental stability and facile synthesis. PANI used as CE material is synthesized by
means of either chemical polymerization or electropolymerization method. It is possible to enhance the electrochemical catalytic properties of PANI CEs by the use of
special morphologies. In PANI CEs, dopants are selected such that it enhances conductivity and increases surface area by acting as a pore former. The use of PPy based
CEs in DSCs yield relatively lower efficiencies due to low conductivity and high
R ct . Nevertheless its efficiency is improved by selection of proper dopants, effective
synthetic methodologies and manipulating surface morphologies. Despite lower efficiencies their applicability as a CE material is preferred due to cost effective facile
synthesis and fabrication of PPy based CEs. PEDOT yields the highest efficiency
and electrocatalytic activity towards I
−
3 /I
− amongst other conducting polymers in
Pt free DSCs. The applicability of PEDOT CEs is limited due to its cost which is
comparable with that of Pt CE. Furthermore, carbon materials are used as composite
materials with conducting polymers and conducting polymer blends to prepare CEs
with enhanced conductivity, electrocatalytic properties and favourable mechanical
properties derived through synergistic effects. The use of composite materials consisting of conducting polymers and carbon materials such as CB, CNTs and graphene; as
CE material has yielded outstanding efficiencies in Pt fee DSCs. Hence the prospect
of substitution of Pt CE with conducting polymers and polymer hybrid composites
and preparing cost effective environmentally friendly DSCs seems promising in the
future.
S. S. B. Gunasekera et al.
17.3 Summary
The CE is a vital component in DSCs which is responsible for the transfer of electrons
from the external circuit back to the redox mediator and regeneration of redox couple.
The CE electrode typically comprises of a transparent conductive oxide glass on
which a catalyst is fabricated. The applicability of a wide variety of CE materials
has been investigated out of which Pt has been utilized as the preferred CE material
due to its high conductivity and high electrocatalytic activity towards I
−
3 /I
− . The
applicability of Pt as a CE is limited due to its high cost and susceptibility to undergo
corrosion. Hence the use of substitute materials in place of Pt as the CE; such as carbon
based materials, metal organic frameworks, conducting polymers and polymer hybrid
composites have been extensively investigated.
Conducting polymers are considered as promising CE material due to their high
conductivity, high electrocatalytic activity and good stability. Furthermore their
applicability as CE materials is favoured due to cost effectiveness and feasibility
of synthesis. Various conducting polymers such as PANI, PPy, PEDOT and polymer
hybrid composites have been extensively investigated as cost effective CE materials in Pt free DSCs. PANI based CE material is a promising prospect in DSCs
due to appreciable photovoltaic performances and cost effectiveness. PANI reveals
favourable characteristics such as low cost, high electrochemical activity, high environmental stability and facile synthesis. PANI used as CE material is synthesized by
means of either chemical polymerization or electropolymerization method. It is possible to enhance the electrochemical catalytic properties of PANI CEs by the use of
special morphologies. In PANI CEs, dopants are selected such that it enhances conductivity and increases surface area by acting as a pore former. The use of PPy based
CEs in DSCs yield relatively lower efficiencies due to low conductivity and high
R ct . Nevertheless its efficiency is improved by selection of proper dopants, effective
synthetic methodologies and manipulating surface morphologies. Despite lower efficiencies their applicability as a CE material is preferred due to cost effective facile
synthesis and fabrication of PPy based CEs. PEDOT yields the highest efficiency
and electrocatalytic activity towards I
−
3 /I
− amongst other conducting polymers in
Pt free DSCs. The applicability of PEDOT CEs is limited due to its cost which is
comparable with that of Pt CE. Furthermore, carbon materials are used as composite
materials with conducting polymers and conducting polymer blends to prepare CEs
with enhanced conductivity, electrocatalytic properties and favourable mechanical
properties derived through synergistic effects. The use of composite materials consisting of conducting polymers and carbon materials such as CB, CNTs and graphene; as
CE material has yielded outstanding efficiencies in Pt fee DSCs. Hence the prospect
of substitution of Pt CE with conducting polymers and polymer hybrid composites
and preparing cost effective environmentally friendly DSCs seems promising in the
future.