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S. Peiris et al.
16.1 Introduction
Photovoltaic (PV) energy conversion strategies have attracted huge attention in the
scientific world today. With the depletion of fossil fuel deposits, the world is at the
brim of facing an energy crisis; Utilization of solar energy is a hot spot of current
research in this regard. Although photovoltaics date back nearly 175 years, development of photovoltaic cells progressed sporadically, and only became a viable energy
source with the discovery of p-n junction silicon photocells, which could achieve an
efficiency of 6%. Advances have improved efficiencies to over 20%, and currently,
silicon based solar cells are a prime candidate for efficient photo current generation
(Nattestad et al. 2016; Fraas 2014; Hagfeldt et al. 2010; Venkatraman et al. 2018).
Silicon being the most abundant element on the earth’s crust facilitates easy access.
Moreover, using Si cells are stable to ambient temperatures (Chapin et al. 1957),
minimize reflection losses and monocrystalline silicon solar cells have relatively high
photo conversion efficiencies. These cells are thought of as first-generation solar cells.
Since the purification process of silicon is expensive, it has become the bottleneck
for large scale commercial application. As a result, thin film solar cells composed
of amorphous silicon, CIGS (copper indium gallium diselenide), and CdTe, which
belong to the second generation of solar cells, came into play. However, the photo
conversion efficiencies obtained with these devices are lower compared to those of
monocrystalline silicon (Hagfeldt et al. 2010). Among other thin film solar cells,
amorphous silicon is the most established technology due to advantages like lower
temperature coefficient for power loss, low toxicity and cost effectiveness (Shah
et al. 1995). A vast array of scientific approaches is being implemented to develop
affordable and clean energy based on silicon solar cells (Chapin et al. 1954, 1957;
Hagfeldt et al. 2010).
A subsequent stage in the field of photovoltaics was the development of the dyesensitized solar cell (DSC), which is one of the outstanding inventions with an environmentally friendly, low cost and feasible practical application. DSCs are regarded
as a bridge that directs the functionality of solar cells towards the third generation
(O’regan and Grätzel 1991). Michael Grätzel and Brian O’Regan published their
seminal work on DSCs in 1991, reporting a 7% overall light-to-electricity energy
conversion yield under diffused sunlight (Hagfeldt et al. 2010; Baxter 2012). From
that point onwards many developments and advancements to DSCs have brought
about higher efficiencies. In 2006, Chiba et al. achieved an efficiency of 11.1%,
which is the highest certified energy conversion reported (Chiba et al. 2006). By 2013,
Kakiage et al. reported a conversion efficiency over 14% by co-photosensitization
with an alkoxy silyl-anchor dye and a carboxy-anchor organic dye (Kakiage et al.
2015). This illustrates the fast evolution of DSCs within a few years. Michael Grätzel
states “Our present needs could be met by covering 0.1% of the Earth’s surface with
PV installations that achieve a conversion efficiency of 10%” (Fraas 2014; Grätzel
2007). Consequently, it is possible PVs could dominate the world’s energy market; bringing sustainable energy generation with low levels of pollution. Figure 16.1
shows renewable electricity generation, with projections to 2050, published by U.S.
S. Peiris et al.
16.1 Introduction
Photovoltaic (PV) energy conversion strategies have attracted huge attention in the
scientific world today. With the depletion of fossil fuel deposits, the world is at the
brim of facing an energy crisis; Utilization of solar energy is a hot spot of current
research in this regard. Although photovoltaics date back nearly 175 years, development of photovoltaic cells progressed sporadically, and only became a viable energy
source with the discovery of p-n junction silicon photocells, which could achieve an
efficiency of 6%. Advances have improved efficiencies to over 20%, and currently,
silicon based solar cells are a prime candidate for efficient photo current generation
(Nattestad et al. 2016; Fraas 2014; Hagfeldt et al. 2010; Venkatraman et al. 2018).
Silicon being the most abundant element on the earth’s crust facilitates easy access.
Moreover, using Si cells are stable to ambient temperatures (Chapin et al. 1957),
minimize reflection losses and monocrystalline silicon solar cells have relatively high
photo conversion efficiencies. These cells are thought of as first-generation solar cells.
Since the purification process of silicon is expensive, it has become the bottleneck
for large scale commercial application. As a result, thin film solar cells composed
of amorphous silicon, CIGS (copper indium gallium diselenide), and CdTe, which
belong to the second generation of solar cells, came into play. However, the photo
conversion efficiencies obtained with these devices are lower compared to those of
monocrystalline silicon (Hagfeldt et al. 2010). Among other thin film solar cells,
amorphous silicon is the most established technology due to advantages like lower
temperature coefficient for power loss, low toxicity and cost effectiveness (Shah
et al. 1995). A vast array of scientific approaches is being implemented to develop
affordable and clean energy based on silicon solar cells (Chapin et al. 1954, 1957;
Hagfeldt et al. 2010).
A subsequent stage in the field of photovoltaics was the development of the dyesensitized solar cell (DSC), which is one of the outstanding inventions with an environmentally friendly, low cost and feasible practical application. DSCs are regarded
as a bridge that directs the functionality of solar cells towards the third generation
(O’regan and Grätzel 1991). Michael Grätzel and Brian O’Regan published their
seminal work on DSCs in 1991, reporting a 7% overall light-to-electricity energy
conversion yield under diffused sunlight (Hagfeldt et al. 2010; Baxter 2012). From
that point onwards many developments and advancements to DSCs have brought
about higher efficiencies. In 2006, Chiba et al. achieved an efficiency of 11.1%,
which is the highest certified energy conversion reported (Chiba et al. 2006). By 2013,
Kakiage et al. reported a conversion efficiency over 14% by co-photosensitization
with an alkoxy silyl-anchor dye and a carboxy-anchor organic dye (Kakiage et al.
2015). This illustrates the fast evolution of DSCs within a few years. Michael Grätzel
states “Our present needs could be met by covering 0.1% of the Earth’s surface with
PV installations that achieve a conversion efficiency of 10%” (Fraas 2014; Grätzel
2007). Consequently, it is possible PVs could dominate the world’s energy market; bringing sustainable energy generation with low levels of pollution. Figure 16.1
shows renewable electricity generation, with projections to 2050, published by U.S.