with commonly used building blocks, like fluorene, carbazole,
0
0
dithieno[3,2-b:2 ,3 -d]silole and BDT, this new polymer exhibits
smaller band gap and moderate HOMO and LUMO levels.
A PCE of 5% has been achieved by using this polymer as
electron donor in a PSC device. Considering the broad response
range and the high Voc of the PBDFDTBT-based PSC device,
PBDFDTBT should be a potential photovoltaic material.
More importantly, these results indicate that BDF would be a
promising building block for highly efficient and biodegradable
photovoltaic materials.
Fig. 2 J–V curves of the PSCs based on PBDFDTBT/PC70BM with
This work was supported by National High-tech R&D
Program of China (863 Program) (No. 2011AA050523) and
Chinese Academy of Sciences and National Natural Science
Foundation of China (NSFC) (No. 51173189, 21104088).
different donor/acceptor ratios (1: 0.5, 1 : 0.8, 1 : 1, 1.1.5, 1 : 2 and 1 : 1.5
ꢀ2
annealing treatment) under illumination of AM 1.5G, 100 mW cm
.
Notes and references
1
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curves of PBDFDTBT-based PSCs before and after thermal annealing
with a D/A ratio of 1 : 1.5.
Charge carrier mobility is another important parameter for
conjugated polymers. The hole mobility of the PBDFDTBT/
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(
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7
dependent Poole–Frenkel Law with a device structure of
ITO/PEDOT:PSS/polymer:PC70BM/Au, and a hole mobility
of 8.96 ꢂ 10ꢀ cm V
4
2
ꢀ1 ꢀ1
s was recorded. The atomic force
microscope (AFM) images of the active layers before and after
thermal annealing treatments are shown in the ESI.w It can be
seen that the blend film (w/w, 1 : 1.5) became smoother after
annealing.
6
7
8
The external quantum efficiency (EQE) curves of the devices
before/after annealing treatment (D/A ratio, 1 : 1.5) are shown
in Fig. 3. In comparison with the device before annealing,
EQE of the annealed device increased obviously. The variation
between the calculated Jsc from the EQE curve and the Jsc
from J–V measurement is within 8%. Furthermore, based on
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ꢀ2
a Jsc of 17 mA cm should be achievable if the EQE of the
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In conclusion, a furan-based conjugated component, BDF,
was firstly used as a building block, and a new polymer,
named PBDFDTBT, was designed, synthesized and applied
in PSCs. The band gap, HOMO and LUMO levels of this new
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In comparison with the other four representative polymers
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This journal is c The Royal Society of Chemistry 2012