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To explore the effect of hydrogen bonding on organic semiconductors, four novel benzo[ b ]thiophene-benzo[ b ]furan analogues with contorted configuration were synthesized and exhibited good solubility in normal solvents. The optical, electrochemical characteristics and DFT simulated calculations demonstrates that the configuration feature of molecule plays an important role in modulating the π-conjugated delocalized degree. The X-ray crystallography further revealed the significant effect of hydrogen bonding on the planarity and aggregation mode of the molecular solid-state structure. The single-crystalline field effect transistor (FET) devices were fabricated and both compounds exhibit excellent FET performance with mobility over 0.8 cm 2 V −1 s −1 . All the results suggest that it would be an effective method to balance the solubility and electrical properties of organic π -conjugated compounds through regulating the molecular configuration by introduction of the hydrogen bonds. [ABSTRACT FROM AUTHOR]

Eu 3+ -activated red emitting phosphors based on the layered perovskite ion conductors A 2 La 2 Ti 3 O 10 :Eu 3+ (A = Na, K) were successfully synthesized by a modified sol-gel method. Photoluminescence excitation (PLE), emission (PL) spectra and cathode-luminescence (CL) spectra were used to characterize the luminescent properties of samples A 2 La 2 Ti 3 O 10 :Eu 3+ (A = Na, K). The band gap and electronic structure of A 2 La 2 Ti 3 O 10 (A = Na, K) were analyzed by the density functional theory (DFT) calculation using the generalized gradient approximation (GGA). The temperature-dependent PL spectra were measured to investigate the thermal stabilities. Their conductivities have also been characterized by the measurements of alternating current (AC) impedance in the range of 200–500 °C over a frequency of 40 Hz–110 MHz, and the diffusional pathways of K and Na ions were also proposed using the bond valence maps (BVM). Results indicates that the phosphor K 2 La 1.0 Eu 1.0 Ti 3 O 10 offers more excellent performance in quantum efficiency, thermal stability and conductivity than those of Na 2 La 1.0 Eu 1.0 Ti 3 O 10 , which shows their potential applications in LEDs and FEDs as a suitable red-emitting phosphor. [ABSTRACT FROM AUTHOR]

Perovskite compounds are always the focus in the material research field. Herein, the polycrystalline samples and single crystals of Na 2 ZrTeO 6 , a B-site ordered double-perovskite compound, were prepared successfully. Single crystal X-ray diffraction demonstrated that Na 2 ZrTeO 6 crystallizes in the cubic space group Fm-3m (No. 225) with unit parameters of a = b = c = 7.80360(10) Å. The crystal structure of Na 2 ZrTeO 6 , formed by ZrO 6 and TeO 6 octahedra through sharing the corner oxygen atoms, belongs to the typical rock-salt-type perovskite structure. The density functional theory calculations show that Na 2 ZrTeO 6 has a direct band gap with band gap of 3.21 eV, which is lower than the experimental value of 3.85 eV. Interestingly, the powder samples of Na 2 ZrTeO 6 exhibit a self-activated near-infrared emission centered at 780 nm under ultraviolet light excitation. And a strong luminescence thermal stability was also observed. Compared to room temperature, the luminescence intensity can maintain 64 % at 200 °C. [Display omitted] • The high-purity double-perovskite Na 2 ZrTeO 6 samples were synthesized by wet chemical method. • Structure analysis indicate that Na 2 ZrTeO 6 belongs to the typical rock-salt-type perovskite structure. • Na 2 ZrTeO 6 exhibits self-activated near-infrared emission centered at 780 nm excited by 308 nm. • The sample's emission intensity maintained 64 % of its room temperature peak intensity at 200 °C. [ABSTRACT FROM AUTHOR]

First-principles calculations were carried out to calculate the formation energy, migration barrier and electronic properties of a resistive memory model based on hexagonal boron nitride (h-BN) in the presence of an active metal and a boron vacancy (V B) using density functional theory (DFT). Following the benchmark of the exchange correlation functional and the calculated parameters of monolayer h-BN, a model of a multilayer h-BN vertical stack with distribution states of SW-5577 defects was proposed. For four active metal dopants (Ti, Ag, Cu and Ni), a preference towards substitution sites (S1) with the lowest dopant formation energies (DFEs) was identified, which enhanced the formation of adjacent V B , especially for the nearest neighbour. Furthermore, a low concentration of Ti dopant in the closest location to the initial position of the migration path would drastically reduce the migration barrier of the V B between layers. Finally, Ti dopants with two and three V B neighbours in the same layer significantly improved the conductivity and the formation of conducting channels because of the improvement of charge distribution in the resistance model, which was demonstrated by DOS plots, band-decomposed charge density and Bader charge. Our present work can provide theoretical guidance for the rational design and device optimization of h-BN-based RRAM devices. • A multilayer vertical stack with SW-5577 defects was proposed for theoretical calculation of h-BN based RRAM. • A preference towards substitution site (S1) with the lowest DFEs was identified for Ti, Ag, Cu and Ni dopants. • The closest Ti dopant to the initial position would drastically reduce the migration barrier of the V B between layers. • The increase in the number and spatial distribution of V B is beneficial to the surrounding electron localization. [ABSTRACT FROM AUTHOR]