4 research outputs found
Synthesis of an AcceptorāDonorāAcceptor Multichromophore Consisting of Terrylene and Perylene Diimides for Multistep Energy Transfer Studies
Motivated by the results obtained
from the investigation of singletāsinglet
annihilation in a linear multichromophore comprising terrylene diimides
(TDI) and perylene diimide (PDI) in 2010, we report the detailed process
toward the successful synthesis of a TDIāPDIāTDI dyad.
Ineffective synthetic pathways, which were necessary for the understanding
of the step-by-step construction of the complex multichromophore,
are described, leading toward a universal synthetic plan for multicomponent
systems containing rylene diimides separated by rigid oligophenylene
spacers
Synthesis, Ensemble, and Single Molecule Characterization of a Diphenyl-Acetylene Linked Terrylenediimide Dimer
The synthesis and the photophysical
characterization at the ensemble
and single molecule level of a terrylenediimide (TDI) dimer are reported.
The spectroscopic experimental data are compared with those obtained
for the corresponding model compound TDI. Steady-state and ps time-correlated
single photon counting have shown that both chromophores in the TDI
dimer are in the weak coupling regime allowing their interaction by
FoĢrster resonance energy transfer. Femtosecond transient absorption
experiments showed an excitation power dependence of the fluorescence
decay, which could indicate the occurrence of singletāsinglet
annihilation. Single molecule intensity traces were investigated for
the TDI dimer and suggested two intensity levels. For both intensity
levels several parameters among which emission maximum, fluorescence
decay times, antibunching, blinking off-times and rate of dark state
formation were compared. The blinking analysis revealed that the yield
of dark state formation is an order of magnitude higher when the two
chromophores are still active compared to the case where one is photobleached.
The off-times remain however similar
Enhanced Photocurrent Density by Spin-Coated NiO Photocathodes for NāAnnulated Perylene-Based pāType Dye-Sensitized Solar Cells
The
low photocurrent density of p-type dye-sensitized solar cells (p-DSSCs)
has limited the development of high-efficiency tandem cells due to
the inadequate light-harvesting ability of sensitizers and the low
hole mobility of semiconductors. Hereby, two new āpush-pullā
type organic dyes (PQ-1 and PQ-2) containing N-annulated perylene
as electron donor have been synthesized, where the PQ-2-based p-DSSCs
show higher photoelectric conversion efficiency (PCE) of 0.316% owing
to the higher molar extinction compared to of that PQ-1. Additionally,
the photocurrent densities were remarkably increased from 2.20 to
5.85 mA cm<sup>ā2</sup> for PQ-1 and 2.45 to 6.69 mA cm<sup>ā2</sup> for PQ-2 by spin-coated NiO photocathode based-p-DSSCs,
respectively. This results are ascribed to the enhancement of hole
transport rate, dye-loading amounts and transparency of NiO films
in comparison to that prepared by screen-printing method. Electrochemical
impedance spectroscopy and theoretical calculations studies indicate
that the molecular dipole moment approaching closer to the NiO surface
shifts the quasi-Fermi level to more positive levels, improving open-circuit
voltage (<i>V</i><sub>oc</sub>). Intensity-modulated photocurrent
spectroscopy illustrates that the hole transit time in NiO films prepared
in spin-coating is shorter than that prepared by screen-printing method
Photophysical Investigation of Cyano-Substituted Terrylenediimide Derivatives
Two new terrylenediimide (TDI) chromophores
with cyano substituents
in the bay and core area (BCN-TDI and OCN-TDI, respectively) have
been characterized by a wide range of techniques, and their applicability
for stimulated emission depletion (STED) microscopy has been tested.
By cyano substitution an increase of the fluorescence quantum yield
and a decrease of the nonradiative rate constant is achieved and attributed
to a reduced charge-transfer character of the excited state due to
a lower electron density of the TDI core. For BCN-TDI, the substitution
in the bay area induces a strong torsional twist in the molecule which,
similar to phenoxy bay-perylenediimide (PDI), has a strong effect
on the fluorescence lifetime but appears to prevent the aggregation
that is observed for OCN-TDI. The single-molecule photobleaching stability
of BCN- and OCN-TDI is lower than that of a reference TDI without
cyano substitution (C7-TDI), although less so for OCN-TDI. The photophysical
properties of the excited singlet state are only slightly influenced
by the cyano groups. The observed intense stimulated emission, the
pumpādumpāprobe experiments, and STED single-molecule
imaging indicate that STED experiments with the cyano-substituted
TDIs are possible. However, because of aggregation and more efficient
photobleaching, the performance of BCN- and OCN-TDI is worse than
that of the reference compound without cyano groups (C7-TDI). Bay-substituted
TDIs are less suitable for STED microscopy