Organic
redox-active molecules have been identified as promising
cathodes for practical usage of potassium-ion batteries (PIBs) but
still struggle with serious dissolution problems and sluggish kinetic
properties. Herein, we propose a pseudocapacitance-dominated novel
insoluble carbonyl-based cathode, [2,6-di[1-(perylene-3,4,9,10-tetracarboxydiimide)]anthraquinone,
AQ–diPTCDI], which possesses high reversible capacities of
150 mAh g–1, excellent cycle stability with capacity
retention of 88% over 2000 cycles, and fast kinetic properties. The
strong intermolecular interactions of AQ–diPTCDI and in situ formed cathode electrolyte interphase films support
it against the dissolution problem. The high capacitive-like contribution
in capacities and fast potassium-ion diffusion enhance its reaction
kinetics. Moreover, a symmetric organic potassium-ion battery (OPIB)
based on AQ–diPTCDI electrodes also exhibits outstanding K-storage
capability. These results suggest that AQ–diPTCDI is a promising
organic cathode for OPIBs and provide a practicable route to realize
high-performance K storage.
Symmetry-breaking
charge separation (SB-CS) provides a very promising
option to engineer a novel light conversion scheme, while it is still
a challenge to realize SB-CS in a nonpolar environment. The strength
of electronic coupling plays a crucial role in determining the exciton
dynamics of organic semiconductors. Herein, we describe how to mediate
interchromophore coupling to achieve SB-CS in a nonpolar solvent by
the use of two perylenediimide (PDI)-based trimers, 1,7-tri-PDI and 1,6-tri-PDI. Although functionalization at the
N-atom decreases electronic coupling between PDI units, our strategy
takes advantage of “bridge resonance”,
in which the frontier orbital energies are nearly degenerate with
those of the covalently linked PDI units, leading to enhanced interchromophore
electronic coupling. Tunable electronic coupling was realized by the
judicious combination of “bridge resonance” with N-functionalization. The enhanced
mixing between the S1 state and CT/CS states results in
direct observation of the CT band in the steady-state UV–vis
absorption and negative free energy of charge separation (ΔG
CS) in both chloroform and toluene for the two
trimers. Using transient absorption spectroscopy, we demonstrated
that photoinduced SB-CS in a nonpolar solvent is feasible. This work
highlights that the use of “bridge resonance” is an effective way to control exciton dynamics of organic
semiconductors.
Perylene
diimide (PDI) and the vinylene-bridged helical PDI oligomers
are versatile building blocks for constructing nonfullerene acceptors
(NFAs). In this contribution, a benzene-cored star-shaped NFA, namely, TPDI2-Se, was designed and synthesized for organic solar cells
(OSCs). The NFA with smaller π-conjugated blades, namely, TPDI-Se, was synthesized for comparison. Using the commercially
available PTB7-Th as the electron donor, the best power conversion
efficiency (PCE) of 3.62% was obtained for TPDI-Se-based
OSCs. However, a much higher PCE of 8.59% was achieved for TPDI2-Se-based devices owing to the π-extension in the peripheral panels.
Moreover, the photovoltaic performance of TPDI2-Se-based
OSCs is also superior to those of the parent NFA TPDI2 (PCE of 7.84%)-
and the blade moiety PDI2-Se (PCE of 6.61%)- based ones. Additionally,
a remarkable short-circuit current (J
sc) value of 17.21 mA/cm2 was obtained for TPDI2-Se-based OSCs, which is among the highest J
sc values reported in PDI-based OSCs. These results argue that the
so-called “three in one” molecule design strategy of
π-extension, selenium incorporation, and trimerization offers
a robust approach to constructing high-performance PDI-based NFAs.
Isomerism heavily influences the optoelectronic properties and self-assembly behavior of compounds and subsequentlyaffects their device performance. Herein, two pairs of isomeric perylene diimide( PDI) dimers, PDI and PDI2, were designeda nd synthesized.T he electron-deficient 9,10-anthraquinone group was employed as the bridge, and thus, the resultant dimers exhibited an acceptor-acceptoracceptor (A-A-A) structure. To determine the isomeric effects on the optoelectronicp roperties and photovoltaic performance of these dimers,t heir absorptivity,l uminescence, and redox behavior weres tudied. Bulk heterojunction organic solar cells based on these four dimers were fabricated and measured. The two PDI dimers exhibitedc lear differences in photovoltaic performance, whereas the two PDI2 analoguess howed similar powerc onversion efficiencies( PCEs). The PCEs of the two PDI2 dimers are much higher than those of the PDI dimers. These results illustrate that the isomeric effect of PDI dimers is much larger than that of PDI2 dimers on the device performance, and propere xpansion of conjugation could improve the devicep erformance.
A helical perylene diimide oligomer (PDI2) is gradually emerging as a promising building block for the construction of organic optoelectronic materials.
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