15 research outputs found
Simulation of wave-induced alongshore current during high waves at Haeundae beach, Korea
Strong wave-induced currents frequently develop at Haeundae Beach, Korea. Rip currents at the beach have threatened safety of swimmers in water. Near-shore currents at Haeundae Beach during a high wave time were measured on 4 June 2008 by using drogues equipped with GPS. The current field during measurement period showed westward flow along shoreline. Major driving force of the measured currents is thought to be the wave-induced force, and the tide-induced force was the second important driving force at the time. The wave-induced current field at the time is quantitatively described by using a numerical modelling system CST3D which adopts rearrangement of driving wave-induced forces, and the PESM for computation of advection terms. The computed wave-induced current field agrees reasonably well with the drogue measurements. The numerical model predicts development of rip current around the beach centre for S wave case, the result of which could be used for warning of possible rip current development at the site
Indolo[3,2-b]indole-Containing Donor-Acceptor Copolymers for High-Efficiency Organic Solar Cells
The organic solar cell (OSC) performance of a series of new donor-acceptor copolymers containing indolo[3,2-b]indole as a key donor block and benzothiadiazole (BT) units with various degrees of fluorination as acceptors is reported. Compared with the simple carbazole unit, the strategically developed indolo[3,2-b]indole unit is found to significantly extend π-conjugation and thus increase the intermolecular interactions of the resulting copolymer, as probed by density functional theory calculations, photophysical studies, and structural/morphological analyses. In addition, fluorination of BT can facilitate nanostructuring of the copolymers, mainly due to further planarization of the backbone, which leads to apparently higher hole/electron charge carrier mobilities. The OSC properties of this series of new copolymers blended with fullerene show a strong dependence on the fine and continuous fibrous nanostructure of the blend film. The indolo[3,2-b]indole-based copolymer with singly fluorinated BT units possesses optimal intermolecular interactions and achieves the highest power conversion efficiency of 8.84% under AM 1.5G illumination. This result shows the potential of π-extended carbazole moieties for achieving high-performance OSCs with many of the favorable properties induced by large heteroacene blocks. © 2017 American Chemical Society.1
Synthesis of a Low-Bandgap Fluorinated Donor–Acceptor Copolymer and Its Optoelectronic Application
We demonstrate the
synthesis of a new copolymer which is composed of dialkyl thienylated
benzodithiophene and perfluororalkyl-carbonyl thienothiophene (DTBDT-TTFO)
and the characterization of its optoelectronic properties. The introduction
of thienyl groups enabled the extended delocalization of π electrons
in the DTBDT-TTFO backbone and efficient intermolecular charge transport
as proved by the fairly high field effect mobility of 0.02 cm<sup>2</sup>/(V s). The introduction of perfluororalkyl-carbonyl side
chains resulted in a significant red-shift of DTBDT-TTFO in the absorption
spectra and a decrease in the HOMO and LUMO levels. The resulting
energy levels of DTBDT-TTFO were not satisfactory for solar cell applications,
especially in terms of charge separation at the polymer/PCBM interfaces.
Rather, the DTBDT-TTFO showed better energy level matching with the
colloidal nanocrystals (NCs) of CdSe. A photodetector based on the
bulkheterojunction of DTBDT-TTFO and CdSe NCs with coplanar device
geometry resulted in a high photoconductive gain (responsivity higher
than 1A/W under a low operating voltage of 1 V), possibly arising
from electron trapping at CdSe NCs such that the hole can travel along
the detector and its surrounding circuit. More importantly, the photodetector
revealed a time constant of a few hundreds of microseconds, which
means that the response speed of the photodetector is fast enough
for lag-free imaging applications
Indolo[3,2‑<i>b</i>]indole-Containing Donor–Acceptor Copolymers for High-Efficiency Organic Solar Cells
The organic solar cell (OSC) performance
of a series of new donor–acceptor
copolymers containing indolo[3,2-<i>b</i>]indole as a key
donor block and benzothiadiazole (BT) units with various degrees of
fluorination as acceptors is reported. Compared with the simple carbazole
unit, the strategically developed indolo[3,2-<i>b</i>]indole
unit is found to significantly extend π-conjugation and thus
increase the intermolecular interactions of the resulting copolymer,
as probed by density functional theory calculations, photophysical
studies, and structural/morphological analyses. In addition, fluorination
of BT can facilitate nanostructuring of the copolymers, mainly due
to further planarization of the backbone, which leads to apparently
higher hole/electron charge carrier mobilities. The OSC properties
of this series of new copolymers blended with fullerene show a strong
dependence on the fine and continuous fibrous nanostructure of the
blend film. The indolo[3,2-<i>b</i>]indole-based copolymer
with singly fluorinated BT units possesses optimal intermolecular
interactions and achieves the highest power conversion efficiency
of 8.84% under AM 1.5G illumination. This result shows the potential
of π-extended carbazole moieties for achieving high-performance
OSCs with many of the favorable properties induced by large heteroacene
blocks
Solvent additive to achieve highly-ordered nanostructural semicrystalline DPP copolymers: toward a high charge carrier mobility
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