7 research outputs found
Polystyrene-<i>block</i>-Poly(ionic liquid) Copolymers as Work Function Modifiers in Inverted Organic Photovoltaic Cells
Interfacial layers
play a critical role in building up the Ohmic contact between electrodes
and functional layers in organic photovoltaic (OPV) solar cells. These
layers are based on either inorganic oxides (ZnO and TiO<sub>2</sub>) or water-soluble organic polymers such as poly[(9,9-dioctyl-2,7-fluorene)-<i>alt</i>-(9,9-bis(3′-(<i>N</i>,<i>N</i>-dimethylamino)propyl)-2,7-fluorene)] and polyethylenimine ethoxylated
(PEIE). In this work, we have developed a series of novel poly(ionic
liquid) nonconjugated block copolymers for improving the performance
of inverted OPV cells by using them as work function modifiers of
the indium tin oxide (ITO) cathode. Four nonconjugated polyelectrolytes
(n-CPEs) based on polystyrene and imidazolium poly(ionic liquid) (PSImCl)
were synthesized by reversible addition–fragmentation chain
transfer polymerization. The ratio of hydrophobic/hydrophilic block
copolymers was varied depending on the ratio of polystyrene to the
PSImCl block. The ionic density, which controls the work function
of the electrode by forming an interfacial dipole between the electrode
and the block copolymers, was easily tuned by simply changing the
PSImCl molar ratio. The inverted OPV device with the ITO/PS<sub>29</sub>-<i>b</i>-PSImCl<sub>60</sub> cathode achieved the best
power conversion efficiency (PCE) of 7.55% among the synthesized block
copolymers, exhibiting an even higher PCE than that of the reference
OPV device with PEIE (7.30%). Furthermore, the surface properties
of the block copolymers films were investigated by contact
angle measurements to explore the influence of the controlled hydrophobic/hydrophilic
characters on the device performances
Photoaddition Reactions of Acetylpyridines with Silyl Ketene Acetals: SET vs [2 + 2]-Cycloaddition Pathways
Photoaddition reactions of silyl ketene acetals with
2-, 3- and
4-acetylpyridine have been explored. The results show that the acetylpyridines
react with an electron rich, dimethyl-substituted silyl ketene acetal
via a pathway in which excited state single electron transfer (SET)
takes place to produce β-hydroxyesters in high yields. In contrast,
photochemical reactions of the acetylpyridines with an electron deficient,
nonmethyl-substituted silyl ketene acetal generate oxetanes as major
products, which arise via a route involving excited state [2 + 2]-cycloaddition.
In addition, an increase in solvent polarity significantly enhances
the relative efficiencies of the SET processes versus [2 + 2]-cycloaddition
reactions. Importantly, the carbonyl groups rather than the pyridine
moieties in the acetylpyridine substrates participate in both types
of addition reactions. Finally, the results demonstrate that photoinduced
electron transfer (PET)-promoted chemical reactions between acetylpyridines
and electron rich silyl ketene acetals in polar solvent serve as useful
methods to promote β-hydroxyester forming, Claisen or Mukaiyama
condensation reactions under mild conditions
Rational Design, Synthesis, and Characterization of Deep Blue Phosphorescent Ir(III) Complexes Containing (4′-Substituted-2′-pyridyl)-1,2,4-triazole Ancillary Ligands
On
the basis of the results of frontier orbital considerations, 4-substituted-2′-pyridyltriazoles
were designed to serve as ancillary ligands in 2-phenylpyridine main
ligand containing heteroleptic iridium(III) complexes that display
deep blue phosphorescence emission. The iridium(III) complexes, <b>Ir1</b>–<b>Ir7</b>, prepared using the new ancillary
ligands, were found to display structured, highly quantum efficient
(Φ<sub>p</sub> = 0.20–0.42) phosphorescence with emission
maxima in the blue to deep blue 448–456 nm at room temperature.
In accord with predictions based on frontier orbital considerations,
the complexes were observed to have emission properties that are dependent
on the electronic nature of substituents at the C-4 position of the
pyridine moiety of the ancillary ligand. Importantly, placement of
an electron-donating methyl group at C-4′ of the pyridine ring
of the 5-(pyridine-2′-yl)-3-trifluoromethyl-1,2,4-triazole
ancillary ligand leads to an iridium(III) complex that displays a
deep blue phosphorescence emission maximum at 448 nm in both the liquid
and film states at room temperature. Finally, an OLED device, constructed
using an Ir-complex containing the optimized ancillary ligand as the
dopant, was found to emit deep blue color with a CIE of 0.15, 0.18,
which is close to the perfect goal of 0.15, 0.15
Rational Design, Synthesis, and Characterization of Deep Blue Phosphorescent Ir(III) Complexes Containing (4′-Substituted-2′-pyridyl)-1,2,4-triazole Ancillary Ligands
On
the basis of the results of frontier orbital considerations, 4-substituted-2′-pyridyltriazoles
were designed to serve as ancillary ligands in 2-phenylpyridine main
ligand containing heteroleptic iridium(III) complexes that display
deep blue phosphorescence emission. The iridium(III) complexes, <b>Ir1</b>–<b>Ir7</b>, prepared using the new ancillary
ligands, were found to display structured, highly quantum efficient
(Φ<sub>p</sub> = 0.20–0.42) phosphorescence with emission
maxima in the blue to deep blue 448–456 nm at room temperature.
In accord with predictions based on frontier orbital considerations,
the complexes were observed to have emission properties that are dependent
on the electronic nature of substituents at the C-4 position of the
pyridine moiety of the ancillary ligand. Importantly, placement of
an electron-donating methyl group at C-4′ of the pyridine ring
of the 5-(pyridine-2′-yl)-3-trifluoromethyl-1,2,4-triazole
ancillary ligand leads to an iridium(III) complex that displays a
deep blue phosphorescence emission maximum at 448 nm in both the liquid
and film states at room temperature. Finally, an OLED device, constructed
using an Ir-complex containing the optimized ancillary ligand as the
dopant, was found to emit deep blue color with a CIE of 0.15, 0.18,
which is close to the perfect goal of 0.15, 0.15
Rational Design, Synthesis, and Characterization of Deep Blue Phosphorescent Ir(III) Complexes Containing (4′-Substituted-2′-pyridyl)-1,2,4-triazole Ancillary Ligands
On
the basis of the results of frontier orbital considerations, 4-substituted-2′-pyridyltriazoles
were designed to serve as ancillary ligands in 2-phenylpyridine main
ligand containing heteroleptic iridium(III) complexes that display
deep blue phosphorescence emission. The iridium(III) complexes, <b>Ir1</b>–<b>Ir7</b>, prepared using the new ancillary
ligands, were found to display structured, highly quantum efficient
(Φ<sub>p</sub> = 0.20–0.42) phosphorescence with emission
maxima in the blue to deep blue 448–456 nm at room temperature.
In accord with predictions based on frontier orbital considerations,
the complexes were observed to have emission properties that are dependent
on the electronic nature of substituents at the C-4 position of the
pyridine moiety of the ancillary ligand. Importantly, placement of
an electron-donating methyl group at C-4′ of the pyridine ring
of the 5-(pyridine-2′-yl)-3-trifluoromethyl-1,2,4-triazole
ancillary ligand leads to an iridium(III) complex that displays a
deep blue phosphorescence emission maximum at 448 nm in both the liquid
and film states at room temperature. Finally, an OLED device, constructed
using an Ir-complex containing the optimized ancillary ligand as the
dopant, was found to emit deep blue color with a CIE of 0.15, 0.18,
which is close to the perfect goal of 0.15, 0.15
Synthesis of a Zr-Based Metal–Organic Framework with Spirobifluorenetetrabenzoic Acid for the Effective Removal of Nerve Agent Simulants
A new
microporous Zr(IV)-based metal–organic framework (MOF) containing
4,4′,4″,4‴-(9,9′-spirobi[fluorene]-2,2′,7,7′-tetrayl)tetrabenzoic
acid (Spirof-MOF) was synthesized, characterized, and size-controlled
for the adsorption and decomposition of a nerve agent simulant, dimethyl
4-nitrophenylphosphate (DMNP). Spirof-MOF showed a hydrolysis half-life
(<i>t</i><sub>1/2</sub>) of 7.5 min to DMNP, which was confirmed
by using in situ <sup>31</sup>P NMR spectroscopy. Additionally, size-controlled
Spirof-MOFb (∼1 μm) exhibited a half-life of 1.8 min
and 99% removal within 18 min for DMNP. The results show that Spirof-MOF
is a new active material in removing nerve agent simulants by adsorption
and hydrolytic decomposition
Layer-by-Layer Assembled Films of Perylene Diimide- and Squaraine-Containing Metal–Organic Framework-like Materials: Solar Energy Capture and Directional Energy Transfer
We
demonstrate that thin films of metal–organic framework (MOF)-like
materials, containing two perylenediimides (<b>PDICl</b><sub><b>4</b></sub>, <b>PDIOPh</b><sub><b>2</b></sub>) and a squaraine dye (<b>S1</b>), can be fabricated by layer-by-layer
assembly (LbL). Interestingly, these LbL films absorb across the visible
light region (400–750 nm) and facilitate directional energy
transfer. Due to the high spectral overlap and oriented transition
dipole moments of the donor (<b>PDICl</b><sub><b>4</b></sub> and <b>PDIOPh</b><sub><b>2</b></sub>) and acceptor
(<b>S1</b>) components, directional long-range energy transfer
from the bluest to reddest absorber was successfully demonstrated
in the multicomponent MOF-like films. These findings have significant
implications for the development of solar energy conversion devices
based on MOFs