Thioalkyl-FunctionalizedBithiophene (SBT)-Based OrganicSensitizers for High-Performance Dye-Sensitized Solar Cells
2020
A series of 3,3′-dithioalkyl-2,2′-bithiophene
(SBT)-based
organic chromophores were designed and developed for the use in dye-sensitized
solar cells (DSSCs). By appropriate structural modification of the
SBT π-linkers with different alkyl chains and conjugated thiophene
units, chromophore aggregation and interfacial charge recombination
could be suppressed to a remarkable degree. Single-crystal and optical/electrochemical
data clearly show that the SBT core is nearly planar with the torsional
angle <1°, likely via S(alkyl)···S(thiophene)
intramolecular locks. Therefore, this highly π-conjugated unit
should enhance panchromatic light-harvesting and prove to be an excellent
core for organic dye. For comparison, the 3,3′-dialkyl-2,2′-bithiophene
(BT)-based dye was also prepared. Under 1 sun (100 mW cm–2) illumination, an optimized SBT-6 dye-sensitized cell indicates
a short-circuit current density (JSC)
of 17.21 mA cm–2, an open-circuit voltage (VOC) of 0.78 V, and a fill factor (FF) of 0.71,
corresponding to a power conversion efficiency (η) of 9.47%,
which is nearly two times higher than that of alkylated bithiophene
(BT)-based chromophores. Finally, the proposed sensitizer SBT-6 exhibited
an excellent η of 23.57% under the T5 fluorescent illumination
of 6000 lux. To the best of our knowledge, this is the highest power
conversion efficiencies (PCE) value reported to date among the studied
thiophene or bithiophene-based chromophores.
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