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Inorganic Ligand Thiosulfate-Capped Quantum Dots for Efficient Quantum Dot Sensitized Solar Cells
journal contribution
posted on 2017-05-16, 00:00 authored by Zhenwei Ren, Juan Yu, Zhenxiao Pan, Jizheng Wang, Xinhua ZhongThe
insulating nature of organic ligands containing long hydrocarbon tails
brings forward serious limitations for presynthesized quantum dots
(QDs) in photovoltaic applications. Replacing the initial organic
hydrocarbon chain ligands with simple, cheap, and small inorganic
ligands is regarded as an efficient strategy for improving the performance
of the resulting photovoltaic devices. Herein, thiosulfate (S2O32–), and sulfide (S2–) were employed as ligand-exchange reagents to get access to the
inorganic ligand S2O32–- and
S2–-capped CdSe QDs. The obtained inorganic ligand-capped
QDs, together with the initial oleylamine-capped QDs, were used as
light-absorbing materials in the construction of quantum dot sensitized
solar cells (QDSCs). Photovoltaic results indicate that thiosulfate-capped
QDs give excellent power conversion efficiency (PCE) of 6.11% under
the illumination of full one sun, which is remarkably higher than
those of sulfide- (3.36%) and OAm-capped QDs (0.84%) and is comparable
to the state-of-the-art value based on mercaptocarboxylic acid capped
QDs. Photoluminescence (PL) decay characterization demonstrates that
thiosulfate-based QDSCs have a much-faster electron injection rate
from QD to TiO2 substrate in comparison with those of sulfide-
and OAm-based QDSCs. Electrochemical impedance spectroscopy (EIS)
results indicate that higher charge-recombination resistance between
potoanode and eletrolyte interfaces were observed in the thiosulfate-based
cells. To the best of our knowledge, this is the first application
of thiosulfate-capped QDs in the fabrication of efficient QDSCs. This
will lend a new perspective to boosting the performance of QDSCs furthermore.