10
H. Tyagi et al.
absorbing sensitizer is chemisorbed onto the surface of a wide bandgap semiconductor; a redox electrolyte, that is placed in between two electrodes and functions to
regenerate the sensitizer; and a counter electrode, which is a catalyst which accelerates a redox reaction with the electrolyte. Titanium dioxide (anatase phase) is the
most widely used semiconductor material in dye-sensitized solar cells due to its
low cost, chemical stability and optical properties. In this chapter, the literature on
optimizing TiO 2 as a semiconductor material for n-type DSCs is reviewed. The evolution of TiO 2 nanostructures and techniques such as doping, composite preparation
and surface modification are elaborated on. These methods have enhanced both the
chemical and physical properties of TiO 2 nanostructures. Moreover, despite good
overall performance, rapid recombination kinetics are a major disadvantage inherent in TiO 2 . Thus, research has been carried out to substitute TiO 2 with alternative
semiconductor. In view of this, other potential competitors for photo-anode material
are reviewed and assessed. Finally, the prospects of an ideal semiconductor material
for dye-sensitized solar cells is discussed.
Chapter 16: The energy crisis is a global problem that drives investment on renewable energy sources worldwide. Utilization of solar energy has become an effective
strategy for sustainable energy generation, as it has the potential to fill the energy
gap created due to the depletion of fossil fuel. On the ever-extending ladder of solar
harvesting technologies, third generation dye-sensitized solar cells (DSCs) have the
advantages of better cost effectiveness and environmental footprint when compared to
the first-generation silicon solar cells and second-generation thin film photovoltaics.
The ultimate goal of constructing high-efficiency multi-junction devices has set the
target of improving single junction components of DSCs (n- and p-type), separately.
The pace of development of single junction p-DSCs has been much slower than
that of n-DSCs. Discovery of suitable materials and techniques have lifted the performance of n-DSCs to more than 14% since it was first reported in 1991. On the
other hand, p-DSCs have a maximum efficiency of 2.51%. It is important to bridge
the gap between the efficiencies of these single junction configurations, in order to
adopt the concept of multi-junction/tandem-DSCs that have the potential to reach
higher efficiencies by harvesting a larger fraction of the solar spectrum. This chapter
focuses on reviewing literature on development of p-DSCs. First, as an introduction,
the structure, function and kinetics of p-DSCs are described. Next, the two main
factors that affect the overall performance of a p-DSC; light harvesting capacity, and
energy loss within the device, are comprehensively discussed.
Chapter 17: Dye-sensitized solar cells (DSCs) are third generation photovoltaic
devices capable of harvesting solar energy to generate electricity. DSCs have gained
significant research interest during past decades due to its high theoretical power
conversion efficiencies and most importantly the cost effectiveness and environment friendly fabrication process. Firstly, in this chapter, the function of the counter
electrode (CE) in a DSC has been discussed in brief. The CE participates in the
electron transfer from the external circuit back to the redox mediator thereby catalyzing its regeneration reaction. In the state of art DSCs, Pt has been the preferred
CE material. Properties such as promising conductivity and high electrocatalytic
activity towards the process of reduction of I 3
− to I
− which is the typical redox
H. Tyagi et al.
absorbing sensitizer is chemisorbed onto the surface of a wide bandgap semiconductor; a redox electrolyte, that is placed in between two electrodes and functions to
regenerate the sensitizer; and a counter electrode, which is a catalyst which accelerates a redox reaction with the electrolyte. Titanium dioxide (anatase phase) is the
most widely used semiconductor material in dye-sensitized solar cells due to its
low cost, chemical stability and optical properties. In this chapter, the literature on
optimizing TiO 2 as a semiconductor material for n-type DSCs is reviewed. The evolution of TiO 2 nanostructures and techniques such as doping, composite preparation
and surface modification are elaborated on. These methods have enhanced both the
chemical and physical properties of TiO 2 nanostructures. Moreover, despite good
overall performance, rapid recombination kinetics are a major disadvantage inherent in TiO 2 . Thus, research has been carried out to substitute TiO 2 with alternative
semiconductor. In view of this, other potential competitors for photo-anode material
are reviewed and assessed. Finally, the prospects of an ideal semiconductor material
for dye-sensitized solar cells is discussed.
Chapter 16: The energy crisis is a global problem that drives investment on renewable energy sources worldwide. Utilization of solar energy has become an effective
strategy for sustainable energy generation, as it has the potential to fill the energy
gap created due to the depletion of fossil fuel. On the ever-extending ladder of solar
harvesting technologies, third generation dye-sensitized solar cells (DSCs) have the
advantages of better cost effectiveness and environmental footprint when compared to
the first-generation silicon solar cells and second-generation thin film photovoltaics.
The ultimate goal of constructing high-efficiency multi-junction devices has set the
target of improving single junction components of DSCs (n- and p-type), separately.
The pace of development of single junction p-DSCs has been much slower than
that of n-DSCs. Discovery of suitable materials and techniques have lifted the performance of n-DSCs to more than 14% since it was first reported in 1991. On the
other hand, p-DSCs have a maximum efficiency of 2.51%. It is important to bridge
the gap between the efficiencies of these single junction configurations, in order to
adopt the concept of multi-junction/tandem-DSCs that have the potential to reach
higher efficiencies by harvesting a larger fraction of the solar spectrum. This chapter
focuses on reviewing literature on development of p-DSCs. First, as an introduction,
the structure, function and kinetics of p-DSCs are described. Next, the two main
factors that affect the overall performance of a p-DSC; light harvesting capacity, and
energy loss within the device, are comprehensively discussed.
Chapter 17: Dye-sensitized solar cells (DSCs) are third generation photovoltaic
devices capable of harvesting solar energy to generate electricity. DSCs have gained
significant research interest during past decades due to its high theoretical power
conversion efficiencies and most importantly the cost effectiveness and environment friendly fabrication process. Firstly, in this chapter, the function of the counter
electrode (CE) in a DSC has been discussed in brief. The CE participates in the
electron transfer from the external circuit back to the redox mediator thereby catalyzing its regeneration reaction. In the state of art DSCs, Pt has been the preferred
CE material. Properties such as promising conductivity and high electrocatalytic
activity towards the process of reduction of I 3
− to I
− which is the typical redox