354
S. S. B. Gunasekera et al.
current revealed from CV tests and lower charge transfer resistance. These conducting polymers have a rough surface morphology and due to this high surface area the
electrocatalytic activity is been enhanced. Although the power conversion efficiency
is not as high as Pt CE (up to 90% PCE of DSCs using Pt CE) in this case of conducting PANI polymers, it is a preferred CE material due to its cost effectiveness and
facile synthesis methodology (Xiao et al. 2013).
The two step cyclic voltammetry approach for the synthesis of PANI CE material
has also been able to achieve substantial power conversion efficiency. This method
enables the preparation of well controlled and short branched PANI nanofibres with
high performance. It involves a pre electropolymerization step in which a larger
potential range (0–1.3 V) is applied for few cycles (typically one) followed by PANI
electropolymerization subjected to a smaller potential range (0–0.9 V) for a larger
number of cycles (10 cycles). It reveals high electrocatalytic activity towards I
−
3 /I
−
redox couple due to high cathodic peak current and lower charge transfer resistance
as evident from CV tests. This is also due to the enhanced surface area attributed
to PANI nanofibres due to short branched surface morphology. The conversion efficiency of these two step PANI CEs can be enhanced to achieve up to 97% of the
power conversion efficiency observed when platinised CEs are been used. But their
applicability is favoured due to cost effective nature (Xiao et al. 2014).
The surface morphology of electropolymerized PANI has a significant impact
on the electrocatalytic activity and charge transfer resistance in DSCs. This surface
morphology of electropolymerized PANI CEs varies with the usage of different
dopant anions such as SO
2−
4 , ClO
−
4 , BF
−
4 , Cl
− and p-toluene sulfonate (Rahman
et al. 2016).
The use of H 2 SO 4 -doped dense PANI nanoparticles CE has enabled a higher power
conversion efficiency of 7.30% in DSCs. The long conjugation structure, high level
of doping and extensive electron delocalization contributes for favourable electrical
conductance and enhanced electrocatalytic activity towards I
−
3 /I
− redox species thus
owing to an overall higher power conversion efficiency (Rahman et al. 2016).
The electrocatalytic activity and power conversion efficiency of sulfamic aciddoped PANI nanofibres have been enhanced due to the fact that sulfamic acid contributes to create voids in the fibrous network of PANI nanofibres. This doping allows
a 27% improvement in the photon-conversion efficiency (Ameen et al. 2010).
The usage of PANI nano wire arrays as a CE material enables a very high power
conversion efficiency of 8.24%. The oriented PANI nano wire arrays are prepared
by means of in situ polymerization owing to a greater surface area and hence a
high catalytic activity towards the redox mediator. It had been found that a greater
electrocatalytic activity is recorded towards Co
2+ /Co
3+ redox mediator. The usage
of PANI nano wire arrays also associates the advantage of been able to be grown on
flexible substrate material (Wang et al. 2013).
Furthermore transparent PANI CEs have been used for the fabrication of novel
bifacially active DSCs that can be illuminated from both sides. Such bifacially active
DSCs prepared using transparent PANI CEs enables high power generating efficiency
due to the ability of utilizing light from both sides. Bifacial DSCs require transparency
in the CEs; hence the use of a Pt CE is unfavoured due to its high reflectance of
S. S. B. Gunasekera et al.
current revealed from CV tests and lower charge transfer resistance. These conducting polymers have a rough surface morphology and due to this high surface area the
electrocatalytic activity is been enhanced. Although the power conversion efficiency
is not as high as Pt CE (up to 90% PCE of DSCs using Pt CE) in this case of conducting PANI polymers, it is a preferred CE material due to its cost effectiveness and
facile synthesis methodology (Xiao et al. 2013).
The two step cyclic voltammetry approach for the synthesis of PANI CE material
has also been able to achieve substantial power conversion efficiency. This method
enables the preparation of well controlled and short branched PANI nanofibres with
high performance. It involves a pre electropolymerization step in which a larger
potential range (0–1.3 V) is applied for few cycles (typically one) followed by PANI
electropolymerization subjected to a smaller potential range (0–0.9 V) for a larger
number of cycles (10 cycles). It reveals high electrocatalytic activity towards I
−
3 /I
−
redox couple due to high cathodic peak current and lower charge transfer resistance
as evident from CV tests. This is also due to the enhanced surface area attributed
to PANI nanofibres due to short branched surface morphology. The conversion efficiency of these two step PANI CEs can be enhanced to achieve up to 97% of the
power conversion efficiency observed when platinised CEs are been used. But their
applicability is favoured due to cost effective nature (Xiao et al. 2014).
The surface morphology of electropolymerized PANI has a significant impact
on the electrocatalytic activity and charge transfer resistance in DSCs. This surface
morphology of electropolymerized PANI CEs varies with the usage of different
dopant anions such as SO
2−
4 , ClO
−
4 , BF
−
4 , Cl
− and p-toluene sulfonate (Rahman
et al. 2016).
The use of H 2 SO 4 -doped dense PANI nanoparticles CE has enabled a higher power
conversion efficiency of 7.30% in DSCs. The long conjugation structure, high level
of doping and extensive electron delocalization contributes for favourable electrical
conductance and enhanced electrocatalytic activity towards I
−
3 /I
− redox species thus
owing to an overall higher power conversion efficiency (Rahman et al. 2016).
The electrocatalytic activity and power conversion efficiency of sulfamic aciddoped PANI nanofibres have been enhanced due to the fact that sulfamic acid contributes to create voids in the fibrous network of PANI nanofibres. This doping allows
a 27% improvement in the photon-conversion efficiency (Ameen et al. 2010).
The usage of PANI nano wire arrays as a CE material enables a very high power
conversion efficiency of 8.24%. The oriented PANI nano wire arrays are prepared
by means of in situ polymerization owing to a greater surface area and hence a
high catalytic activity towards the redox mediator. It had been found that a greater
electrocatalytic activity is recorded towards Co
2+ /Co
3+ redox mediator. The usage
of PANI nano wire arrays also associates the advantage of been able to be grown on
flexible substrate material (Wang et al. 2013).
Furthermore transparent PANI CEs have been used for the fabrication of novel
bifacially active DSCs that can be illuminated from both sides. Such bifacially active
DSCs prepared using transparent PANI CEs enables high power generating efficiency
due to the ability of utilizing light from both sides. Bifacial DSCs require transparency
in the CEs; hence the use of a Pt CE is unfavoured due to its high reflectance of