Page 431 - Polymer-based Nanocomposites for Energy and Environmental Applications

388 Polymer-based Nanocomposites for Energy and Environmental Applications

2 1
0.76 10 10 to 4.42 10 10 m s , which was very close to that of liquid elect-
2 1
rolyte (4.04 10 10 m s ). They obtained 7.18% PCE from TiO 2 -PVDFHFP
nanocomposite-based DSC that was 1.46% higher than pure PVDFHFP electrolyte-
based one as a result of the lower interfacial charge recombination between the
photoanode and the electrolyte. Additionally, the nanocomposite-based electrolytes
also increased the thermal stability of the DSC.
As an alternative for enhanced electrolyte properties, conductive polymers can be
employed into PGEs in order to boost the liquid electrolyte loading, ionic conducti-
vity, and electrocatalytic activity of the gel toward triiodides. Yuan et al. [113] pro-
duced PGE in which freeze-dried microporous poly(acrylic acid)-poly(ethylene
glycol) (PAA-PEG) blend was employed as matrix for PANi and PPy conducting
polymer. They obtained an ionic conductivity of 19.18 mS cm 1 at 65°C from
PAA-PEG/PANi conducting gel electrolyte, which was very close to that of pure
1
liquid electrolyte (19.22 mS cm ). PCE values of 7.12%, 6.53%, and 5.02% were
obtained from PEG/PANi, PAA-PEG/PPy, and pure PAA-PEG-based DSC, respec-
tively. They explained the working mechanism as the formation of interconnected
conductive channels within the matrix as a result of the incorporation of the con-
ducting polymer molecules into the microporous PAA-PEG matrix. Consequently,
the reduction reaction of triiodide ions can be extended from Pt/gel electrolyte
interface to both the interface and the three-dimensional framework of microporous
conducting gel electrolyte.

13.3 Conclusion

DSC, as a third-generation solar cell technology, is a potential low-cost candidate
to meet the increasing energy demand in the world. Since the first reports on this
technology appeared, about 18,000 research articles have been published. These
researches are focused on low-cost mass production of highly efficient, stable, flexible
solar cells. In this regard, polymer-based composite materials used in flexible DSCs,
their production methods, and effects on performance were reviewed in this chapter.
Polymeric structures can be used as a part of several components in DSC, for exam-
ple, flexible substrates, polymer electrolytes, and catalyst materials in order to
improve the device’s cost/performance ratio. TCO-coated plastic substrates provide
advantages like optical transparency and chemical inertness for the production of
low-cost, higher performance solar cells. Although TCO-coated plastic substrates
give similar conductivity to their counterparts based on glass, the brittleness and insta-
bility of the TCO coating required new transparent conductive coatings/layers such as
graphene, carbon materials, and polymers on plastic substrates.
In order to produce flexible DSCs, deposition of metal oxide-based photoanodes
onto plastic substrate is required at low temperature. But undesired organic impurities
in the mesoporous layer, poor interconnection of particles, poor adhesion of TiO 2 to
the substrate, and unsuitable pore structure when sintering at low temperatures are
main problems for obtaining high-efficient solar cells. Researches like preparing
organic binder-free pastes, new film forming/transfer methods for TiO 2 layers on