Dongzhi Liu

Ambipolar organic semiconductors with cascades of energy levels for generating long-lived charge separated states: a donor–acceptor1–acceptor2 architectural triarylamine dye

A donor–acceptor1–acceptor2 architectural 4-styryltriphenyl amine-based organic semiconductor was synthesized for solar cell applications. Sequential electron transfers together with effective hole transfer lead to a charge separated state lifetime of 650 ns, therefore boosting the short circuit current and efficiency of single layer organic photovoltaic cells.

Enhanced Internal Quantum Efficiency in Dye-Sensitized Solar Cells: Effect of Long-Lived Charge-Separated State of Sensitizers

Effective charge separation is one of the key determinants for the photovoltaic performance of the dye-sensitized solar cells (DSSCs). Herein, two charge-separated (CS) sensitizers, MTPA-Pyc and YD-Pyc, have been synthesized and applied in DSSCs to investigate the effect of the CS states of the sensitizers on the devices efficiency. The CS states with lifetimes of 64 and 177 ns for MTPA-Pyc and YD-Pyc, respectively, are formed via the photoinduced electron transfer (PET) from the 4-styryltriphenylamine (MTPA) or 4-styrylindoline (YD) donor to the pyrimidine cyanoacrylic acid (Pyc) acceptor. DSSCs based on MTPA-Pyc and YD-Pyc exhibit high internal quantum efficiency (IQE) values of over 80% from 400 to 600 nm. In comparison, the IQEs of the charge transfer (CT) sensitizer cells are 10-30% lower in the same wavelength range. The enhanced IQE values in the devices based on the CS sensitizers are ascribed to the higher electron injection efficiencies and slower charge recombination. The results demonstrate that taking advantage of the CS states in the sensitizers can be a promising strategy to improve the IQEs and further enhance the overall efficiencies of the DSSCs.

Preparation and Characterization of E7–PMMA Microcapsules by Solvent Evaporation

Nematic liquid crystal E7 (core) was microencapsulated into the poly(methyl methacrylate) (PMMA, shell) via the solvent evaporation method. The morphology of microcapsules depends importantly on the initial PMMA/E7 ratio in oil phase. Solvent evaporation temperature, as well as the co-solvent, could further influence the surface morphology of microcapsules. Results of optical microscope measurements show that microcapsule shells with smooth surface are transparent. The microcapsule core loading is in accordance with the initial E7 content. The final obtained mononuclear microcapsules exhibit transparent shell, high E7 loading, and decent thermal stability.

Microencapsulation of Cholesteric Liquid Crystal by Combined Method of Solvent Evaporation and Photopolymerization

In this article, UV-curable liquid CBU226 was firstly employed as the shell material to microencapsulate cholesteric liquid crystals (CLCs) by a combined technique of solvent evaporation and photopolymerization. Microcapsule properties depend on the sequence of photopolymerization and solvent evaporation process during preparation. Solvent-evaporation-induced-phase-separation–photopoly-merization process could produce microcapsules with high core loading and spherical core/shell structure. Specifically, spherical CLC microcapsules with mononuclear structure, smooth surface, and high CLC loading (97.34 wt%) were prepared. After drying, the microcapsules could easily deform to nonspherical geometry and exhibit vivid color, showing great potential for the application of display devices.

Syntheses and properties of PVK modified with perylene structures

Abstract A perylene dye monomer, N -(3,5-dimethyl-) phenenyl- N′ -allyl-3,4:9,10-perylene tetracarboxylic diimide, was synthesized and copolymerized with N -vinyl carbarzole to produce perylene-modified PVK structures. The monomeric and polymeric dyes were characterized by infrared, absorption, and fluorescence spectroscopies, the results of which indicated little difference between the two forms. Intrinsic viscosity studies revealed that the molecular weights of the polymeric dyes were not very high.

Tuning photophysical properties via alkoxyl groups in charge-separated triphenylamine sensitizers for dye-sensitized solar cells

Abstract Two charge-separated (CS) sensitizers ( MoTPA-Pyc and OcTPA-Pyc ) with methoxyl or octyloxyl groups attached to the para position of the triphenylamine donor moiety were synthesized to investigate the effect of the alkoxyl groups on the photophysical properties of the CS sensitizers and photovoltaic performances of the corresponding dye-sensitized solar cells (DSSCs). The introduction of alkoxyl groups can increase the energy gap between LUMO+1 and LUMO, leading to an increased intramolecular photo-induced electron transfer (PET) efficiency. Both MoTPA-Pyc and OcTPA-Pyc show elongated lifetimes for their CS states, resulting in an enhanced internal quantum efficiency (IQE) of DSSCs. It has been demonstrated that intramolecular PET is the key step for efficient DSSCs due to the presence of long-lived CS states allowing efficient and fast interfacial electron transfer from the CS sensitizers to the TiO 2 nanoparticles. The best efficiency of 5.76% was achieved by the MoTPA-Pyc based DSSC through a combined contribution of high IQE and efficient light harvesting. The results suggest that enhancing the intramolecular PET efficiency and the light harvesting ability of the dye-loaded TiO 2 film are effective strategies for achieving higher photovoltaic performance for CS sensitizer-based DSSCs.

Facile Synthesis of [1,2,4]Triazolo[4,3-a]pyrazin-3-amines via Oxidative Cyclization of 1-(Pyrazin-2-yl)guanidine Derivatives

In this study, we applied a novel, mild, and convenient synthetic method involving the oxidative cyclization of 1-(pyrazin-2-yl)guanidine derivatives to produce [1,2,4]triazolo[4,3-a]pyrazin-3-amines. We optimized the reaction procedure to easily obtain 5-chloro-[1,2,4]triazolo[4,3-a]pyrazin-3-amine. Various types of halogenated pyrazines can successfully undergo this process. We synthesized a series of 1-(pyrazin-2-yl)guanidines and [1,2,4]triazolo[4,3-a]pyrazin-3-amines, and then elucidated their structures based on their 1H-NMR, 13C-NMR, ESI-HRMS, and nuclear Overhauser effect spectra.

Synthesis and spectral property study of porphyrin-anthraquinone dyads bonded through azo

To determine if the dihedral angle between the phenyl group and the porphyrin ring in the meso-phenyl porphyrin (H2TPP) could be adjusted by selective substitution of the naphthyl group for phenyl groups, novel dyads with a free-base porphyrin donor and anthraquinone acceptor linked by a rigid azo bond were synthesized and their spectral properties were investigated in detail. The Soret absorption band of dyads with meso-naphthyl groups in porphyrin shows 5–7 nm red shift as compared to the corresponding raw materials due to the introduction of the anthraquinone moiety. Fluorescence from the porphyrin moiety was found to be intensely quenched with the addition of anthraquinone moiety in the dyads; the highest quenching rate was observed to be 95% in the dyad prepared by meso-tetranaphthyl porphyrin. This indicates that the efficiency of the intramolecular photoinduced electron transfer in porphyrin-anthraquinone dyads could be changed by substituting the meso-phenyl group in porphyrin for the meso-naphthyl group.

2-(4-Methyl-2-phenyl-piperazin-4-ium-1-yl)pyridine-3-carboxyl-ate dihydrate.

The title compound, C17H19N3O2·2H2O, is particularly useful in the preparation of mirtazapine, which is the active agent in a new class of antidepressants. It crystallized as a zwitterion with two molecules of water in the asymmetric unit. The crystal structure is dominated by a system of hydrogen bonds involving the positively charged N atom and both water molecules.

4-(3,4-Dichloro-phen-yl)-3,4-dihydronaphthalen-1(2H)-one.

The title compound, C16H12Cl2O, was synthesized from 1-naphthol and 1,2-dichlorobenzene with anhydrous aluminium chloride as a cataylst. In the molecule, the two ring systems are approximately perpendicular to one other with a dihedral angle of 82.06 (4)°. There are two CH-type hydrogen bonds.