Environmental Engineering Reference
In-Depth Information
8.3.6 Section Summary
The effects of Au NPs incorporated into the active layer PFSDCN:PCBM of OSCs
have been described in this section. Theoretical simulations indicated that the near
field of NPs distribute laterally along the active layer, leading to the absorption
improvement which is also experimentally observed. On the other hand, electrical
properties of these OSCs are also described. The carrier mobility is found to
increase upon incorporation of NPs. In particular, hole mobility increased to a
larger extent than electron mobility, leading to reduced carrier transport imbal-
ance. Exciton dissociation efficiency is found to increase then decrease as NP
concentration is increased. The active layer morphology is also altered after NP
incorporation. These factors together lead to the observed PCE trend.
8.4 Efficiency Improvement of Polymer Solar Cells
by Incorporating Au Nanoparticles
into All Polymer Layers
Although PCE of OSCs has been shown to improve by incorporating metallic NPs
in either the buffer layer such as PEDOT:PSS or the active layer [
6
,
7
,
9
-
11
,
47
,
55
], we have shown in
Sects. 8.2
and
8.3
that in fact, the contribution of LSPR
effects to PCE improvements varies when NPs are doped in different layers.
Electrical properties such as carrier mobility, exciton dissociation probability, and
the morphology of the organic layer incorporated with NPs are affected by NPs,
and are major contributors to the PCE changes as NP concentration increases.
With the experience of incorporating NPs individually in the hole collection layer
or active layer, we noticed that there are very limited studies on incorporating
metallic NPs in more than one organic layer. The study of incorporation of NPs in
all organic layers has two objectives: (1) Achieving high efficiency OSCs by
incorporating NPs within all possible layers of a OSC; (2) Investigating their
effects on the optical and electrical properties, in particular, observing the presence
of interaction between the NPs in different layers, if any. Achieving these two
objectives will enhance our understanding in device mechanisms and is essential
for designing high efficiency NP-incorporated OSCs.
In this work, monofunctional PEG-capped Au NPs of sizes 18 and 35 nm are
doped in the PEDOT:PSS and P3HT:PCBM layers, respectively, leading to an
improvement of PCE by *22 % compared to the optimized control device. We
will first identify the impact of NPs in each polymer layer on OSC characteristics
by doping Au NPs in either the PEDOT:PSS or P3HT:PCBM layer. Then, we will
investigate the impact of Au NPs incorporated in all polymer layers. We dem-
onstrate that the accumulated benefits of incorporating Au NPs in all organic layers
of OSCs can achieve larger improvements in OSC performances.
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