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 TiO₂) 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/PS₂₉-<i>b</i>-PSImCl₆₀ 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_p = 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_p = 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_p = 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>_1/2) of 7.5 min to DMNP, which was confirmed by using in situ ³¹P 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>_<b>4</b>, <b>PDIOPh</b>_<b>2</b>) 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>_<b>4</b> and <b>PDIOPh</b>_<b>2</b>) 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