Chemistry Reference
In-Depth Information
from 250 to 700 nm with narrow optical band gaps of 1.71-2.01 eV. The band gaps and the molecular
electronic energy levels can be tuned by copolymerizing the benzo[1,2-
b
:4,5-
b
]difuran core with
different n-conjugated electron-donating or withdrawing units in different ratios.
N
S
Ar =
NC
O
N
N
Ar
S
x
y
O
CN
N
N
Bulk heterojunction solar cell devices were fabricated by Liu and coworkers, using the copolymers
as the electron donor and ([6,6
0
]-phenyl-C
61
-butyric acid methyl ester) as the electron acceptor. The
preliminary research has revealed power conversion efficiencies of 0.17-0.59% under AM 1.5
illumination (100 mW/cm
2
).
Thompson and coworkers [
281
] point out that despite the correlation between the absorption and
J
SC
, most polymers used in currently high-performing solar cells have limited absorption breadths
and rely largely on band gaps. As a result, there is a heavy reliance on fullerenes (especially on
PC
61
BM, 1-(3-methoxycarbonyl)propyl-1phenyl-[6,6]-methanofullere) to absorb photons in the short
wavelength range and considerable absorption losses in the longer wavelengths. Although fullerenes
absorb in the short wavelength region and are thus complementary to many polymers, they point to
the evidence that 60% of excitons formed in the PC
61
BM phase decay before being harvested and do
not contribute to
J
SC
[
282
]. This research group mixed graphene oxide that acts as a surfactant with
fullerenes C
60
and single-walled carbon nanotubes in water, coated a glass slide with the solution, and
heated it to reduce the graphene oxide to graphene. They claimed that chips using this photovoltaic
layer were much more efficient at converting light into electricity that the organic devices developed
with covalent chemistry.
Simultaneous to doing research on polymeric materials, research is also being carried out on
improving the construction of solar cells. One strategy is to stack two light-absorbing materials in a
tandem cell to harvest greater fraction of the solar spectrum. By inserting gold nanoparticles between
the two layers, Yang Yang and coworkers coupled the two tandem cells and demonstrated a
considerable boost inefficiency of light conversion to electricity [
283
].
Review Questions
Section 10.1
1. How are the support materials utilized? Discuss
Section 10.1.1.1
1. Describe the Merrifield resin.
