Chemistry Reference
In-Depth Information
Table 4.1 Characteristics of hierarchical ''nanoforest'' DSSCs. Reproduced with
permission from ref. 11. Copyright 2013, American Chemical Society.
Backbone
NW length
(mm)
Branching
times
Eciency
(%)
J
sc
(mA
cm
2
)
V
oc
(V)
d
n
3
r
4
n
g
|
9
Symbol
Configuration
FF
LG1
7
0.45
1.52
0.636 0.480
LG2
13
0.71
2.37
0.640 0.486
0
LG3
18
0.85
2.87
0.645 0.484
BG1
7
2.22
7.43
0.681 0.522
1
BG2
2.51
8.44
0.683 0.531
13
.
BG3
2
2.63
8.78
0.680 0.530
nanowire growth. Second, a dense network of crystalline ZnO nanowires can
increase the electron diffusion length and electron collection because the
nanowire morphology provides more direct conduction paths for electron
transport from the point of injection to the collection electrode. Third,
randomly branched nanowires exhibit enhanced light harvesting (light-dye
interaction) without sacrificing ecient electron transport. The upstanding
nanowires are not favorable for light harvesting because photons could
travel between the vertical nanowires without being absorbed by the dye.
Furthermore, branched nanowires can increase light harvesting eciency by
scattering enhancement and trapping.
Herman et al.
12
discuss the branching effect on solar cell eciency further
as shown in Figure 4.4. As the length of the branches increased, the bran-
ches became flaccid and the solar cell eciency increase slowed down be-
cause the effective surface area increase was hindered by the branches
bundling during the drying process and subsequently the dye loading
decreased. The length of the branches of the ZnO nanowire tree grown once
Search WWH ::
Custom Search