Page 432 - Polymer-based Nanocomposites for Energy and Environmental Applications

Polymer nanocomposites for dye-sensitized solar cells 389

plastic substrates, or different posttreatment applications are some of the reported
techniques in the literature. Among them, mechanical pressing is one of the best
approaches to obtain stable and good interconnected TiO 2 layers at low temperature.
Also post treatment with UV light is another option to remove undesired organic
residue from the TiO 2 layer as a result of photodegradation reaction.
Production of flexible, cheap, and efficient CE is also another main problem for
flexible DSCs. The conventional Pt electrode provides the highest performance but
requires high-temperature heat treatment. In addition, the use of rare Pt increases
the costs. Usage of carbon and its derivative-coated flexible polymeric substrates
or conductive polymers and their composite structures are also used as inexpensive,
efficient, and flexible CEs in DSCs. Polymer-based CE catalysts can be deposited by
using various wet techniques like slot die coating and printing technologies at ambient
temperature. Also the production of these polymer-based catalyst electrodes with
nanoporous structures and optimal thickness provides high surface area and facile
electron transport.
Leakage and volatilization of organic solvents from the liquid electrolyte require
perfect sealing that limits the shape and stability of the cells. Besides, problems like
electrolyte-related corrosion of CEs or charge recombination between semiconductor-
liquid electrolyte interfaces shifted research into how to replace liquid electrolytes
with solid or gel electrolytes. Polymer electrolytes, PGEs, and organic/inorganic hole
conductors are some of the suggested alternative solutions for these problems in DSC
applications. But issues like low ionic mobility of polymer or gel electrolyte, low infil-
tration of the polymers into TiO 2 mesoporous layer, and high charge-transfer resis-
tance between electrolyte and electrodes have to be improved. Introduction of
some of inorganic nanoparticles, comonomers, and carbon materials can increase
the ionic conductivity and amorphicity, while composite polymer electrolytes con-
sisting of different molecular weight polymers can provide high interfacial contact
between the electrolyte and electrodes. Furthermore, usage of conductive polymers
into polymer gel electrodes boosts the liquid electrolyte loading, ionic conductivity,
and electrocatalytic activity of the gel toward triiodides.
As a conclusion, DSC technology, which works on the principle on the plant
photosynthesis in nature, uses low-cost and environmentally friendly raw materials
and processing methods with simple and inexpensive equipment. All these factors
make this technology very attractive, and the possibility to use polymers as con-
stituent materials can impart an extra value, lower their cost, and expand their
application.

References

[1] International Energy Outlook, 2016. Electricity-energy information administration. [Cited
2017 February 11];Available from: https://www.eia.gov/outlooks/ieo/electricity.cfm.
[2] Viswanathan B. Energy sources: fundamentals of chemical conversion processes and
applications. 1st ed. Saint Louis: Elsevier; 2016.
[3] Snaith HJ. Perovskites: the emergence of a new era for low-cost, high-efficiency solar
cells. J Phys Chem Lett 2013;4:3623–30.