Quantum Dot-Sensitized Solar Cells - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 90

Fig. 1 Cartoon representing the fundamental principles of sensitized solar cells. Light
photoexcites electron-hole pairs at the QD (vertical green arrow). Photoexcited electron is
injected into the CB of the wide bandgap semiconductor, while hole is regenerated from the redox
level of the liquid electrolyte (or the VB of a solid hole transporting material). Electron in wide
bandgap semiconductor is transported to the electron contact (orange arrow). Redox sytem is
regenerated at the counter electrode and electrons diffuse to the working electrode (purple
arrow). During the transport process electron can recombine with holes in the QDs or in the HTM
(blue dashed arrows)
3 Sensitization with Inorganic Semiconductor
Quantum Dots
Considering the sensitized synthesis, an inorganic semiconductor can be prepared
by several ways and the growth mechanism determines dramatically the perfor-
mance of the photovoltaic device [ 15 , 16 ]. In this chapter, we want to highlight the
potentiality of QDSSCs for the development of low cost photovoltaic devices. In
particular, we will review some of the techniques, most commonly, employed for
the sensitization with inorganic semiconductors. Interestingly, these techniques do
not require any special experimental conditions like vacuum or high temperatures;
this fact is especially attractive for industrial development as it is an effective way
for cost reduction.
Two major strategies have been practically used to sensitize QDs onto the elec-
trodes (a) in situ preparation of QDs on the electrode surface and (b) attachment of
presynthesized Colloidal Quantum Dots (CQDs) on the electrode surface. The
former method includes chemical bath deposition, [ 17 ] successive ionic layer
adsorption/reaction, [ 18 ] electrochemical deposition, [ 19 ] and photochemical
deposition [ 20 ]. The latter exploits, but is not limited to, linker molecules, [ 8 , 21 - 23 ]
direct absorption, [ 16 , 22 , 24 ] spray pyrolysis deposition, [ 25 , 26 ], and electro-
phoretic deposition [ 27 - 30 ]. There are also some examples of the combination of
these two approximations [ 31 , 32 ].