Environmental Engineering Reference
In-Depth Information
Fig. 8.21 The J-
V characteristics of hole-only
devices with Au NPs
incorporated into different
layers with the structure of
ITO/PEDOT:PSS (with or
without Au NPs)/
P3HT:PCBM (with or
without Au NPs)/Au (20 nm)/
Al (100 nm). The symbols are
experimental data while the
lines are fitting curves. Fitting
is done according to the
space-charge limited current
model [
56
]
devices of structure ITO/PEDOT:PSS (with or without Au NPs)/Al, it is found that
the resistance of PEDOT:PSS reduces upon addition of NPs. Both the increased
interfacial
contact
area
and
conductivity
of
PEDOT:PSS
contributes
to
the
2.11 X
cm
2
,
reduction
of
the
series
resistance
of
OSCs
from
3.05
to
and
improvement of FF and PCE.
8.4.3 Effects of Au NPs Incorporated into P3HT:PCBM
Although electrical effects dominantly address the performance improvement
when incorporating Au NPs only in PEDOT:PSS, the mechanism for PCE
improvement is found to be different when NPs are incorporated into the active
layer. In contrast to
Sect. 8.3
, a different active layer material, P3HT:PCBM is
used instead of PFSDCN:PCBM and the device characteristics are investigated
here. As shown in Fig.
8.20
, when NPs are incorporated into the active layer only
(Device C), absorption of the active layer increases over a wide wavelength range.
From the theoretical studies [
56
], it is found that the absorption enhancement
can be explained by LSPRs in the Au NPs excited by the TE polarized light. The
dipoles generated in the Au NPs and the strong near field by LSPRs by Au NPs in
the active layer are shown in Fig.
8.22
. It can be observed that the strong near field
distributes into the active layer and directly enhance the light absorption by the
blended polymers of the active layer.
As a result of the strong near field of NPs which overlaps with the active layer,
the amount of photogenerated excitons is increased, and hence increases the J
sc
of
OSCs. Regarding electrical properties, J-V measurements and fitting on hole-only
devices indicate that the hole mobility of the active layer increases from
8.94 9 10
-4
to 1.19 9 10
-3
cm
2
/V
s. Studies have shown that in P3HT:PCBM,
electron mobility is higher than hole mobility and this carrier imbalance is
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