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Polymer nanocomposites for 13

dye-sensitized solar cells

,†
M.D. Calisir* , E. Stojanovska*, A. Kilic*
†
*Istanbul Technical University, Istanbul, Turkey, Recep Tayyip Erdogan University,
Rize, Turkey

13.1 Introduction

Increase in world population and industrial production causes a huge increment in
global energy demand. According to the report of International Energy Agency, in
2012, total global electricity generation reached up to 21560 TWh of which 68%
was generated from fossil fuels, 11% from nuclear, and 2% from renewable sources
[1]. Considering the limitations in fossil fuel resources and their greenhouse effect on
global warming, energy production via green routes, for example, from renewable
sources, is getting even bigger attention. Wind, tidal, geothermal, and solar sources
are some of renewable energy sources. Among these sources, solar energy is clean
and most abundant form of energy. Sun provides earth energy of 174,000 TW per
year. If we consider that 50% of this energy is lost on reflection, absorption, etc.,
we can assume that 81,780 TW sun energy reaches the earth surface. This energy
4
is nearly 3 10 times higher than global energy consumption [2].
Sunlight either can be used as a heat source for steam-turbine-based electricity
generator or can be directly converted into electricity by a solar (photovoltaic) cell.
Since the 1950s, solar cells have been considered as one of the most important rene-
wable energy sources for the future. Until now, we have witnessed three generations of
solar cells, categorized based on their development time and material used in and the
technology applied [3]:

l The first-generation solar cells are based on elemental silicon and can be either single
crystalline or polycrystalline. Their mechanism depends on the charge separation in a p-n
junction under the influence of incident light. Nowadays, the power conversion efficiencies
(PCEs) of this generation can reach up to 25% [4]. The need for high-quality silicon and also
the high cost of the production equipment moves the focus of the studies toward solutions for
lower cost solar cell.
The second-generation solar cells are based on compound films and amorphous silicon.
l
Cadmium telluride (CdTe, PCE¼19.6%), copper indium gallium diselenide (CIGS,
PCE¼19.8%), gallium arsenide (GaAs, PCE¼28.8%), and amorphous silicon (a-Si,
PCE¼10.1%) are mostly used thin-film structured solar cells [4]. Although this generation
solar cells have lower cost as an advantage, their efficiency is lower than Si-based techno-
logy. Additionally, the usage of rare earth elements like telluride and also toxic materials like
cadmium are some limitations of this technology and require further research [5].

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