Quantum Dot-Sensitized Solar Cells - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 100

Fig. 7 Extinction coefficient
of molecular dye N719, one
of the most popular dyes in
DSSCs, and Sb 2 S 3 inorganic
semiconductor [Boix et al.
[ 185 ] reprint permission from
ACS]
semiconductor QDs sensitizers, it is relatively larger in size than dye molecules;
therefore it is difficult to penetrate deeper parts of TiO 2 electrode and thus limiting
the sensitizer loadings. Therefore, large-pore network is prerequisite to afford
effective QDs loading. On the other hand, such photoanodes could demonstrate
high charge transport from sensitizer to a charge collector, ultimately, over-
whelming the charge recombination at photoanode/electrolyte interface. There-
fore, to achieve (a) high sensitizer loading (b) fast electron transport channel, and
(c) good electrolyte pore-filling, establishing multifunctional photoanode frame
work is the promising approach in QDs-sensitized solar cells. The following
nanostructures has been identified as futuristic architectures in QDSSCs (a) highly
interconnected, spatially assembled 1-D network (b) branched nanowires with
highly conducting backbone which directly attached to charge collector, and (c)
three-dimensionally ordered pore arrays with high scattering capability. Some of
the electrode preparation methods also present a high interest for industrial
application, as electrospinning.
In this context, nanofibrous membrane (NF), inverse opal (IO) and hierarchal
nanowire (HN) electrodes receive great deal of attention as three-dimensional (3-D)
photoanodes for next generation DSSCs or QDSSCs. In this section, we will discuss
the fabrication and advantageous of 3-D nanostructured photoanodes in QDSCs.
4.1 Directly Assembled Continuous Fibrous Electrodes
Utilization of the wide pore-structured nanofibers is receiving great attention for
superficial electrolyte penetration through their vertical pores yield effective
interfacial contacts with TiO 2 -sensitizer interfaces [ 95 , 96 ]. In particular, fibrous
electrodes prepared by an electrospinning technique showed remarkable perfor-
mance in DSSCs since it support large-scale anode fabrication at low cost. Archana
et al. [ 97 ] reported that a 1-D fibrous film results in a high diffusion coefficient