Synthesis and characterization of a three-ring bent-core compound

To investigate the vacuum-deposited films of the banana-shaped mesogens, we prepared a three-ring bent-core (that is, banana-shaped) compound m-bis(4-p- octoxysryrenyl)benzene (m-OSB) and used it as a prototype for studying the related film physics. Herein the synthesis and the structural characterization of m-OSB are reported. 13C and 1H NMR spectra and IR spectrum confirm that m-OSB has a symmetric and all-trans conformation. The results of differential scanning calorimetry, polarizing optical microscopy and X-ray diffractometry indicate that no liquid crystalline phase but two crystalline phases are present in this material: phase I (T<66℃) and phase II (66℃<T<157℃); an isotropic state is observed at above 157℃. Combining the X-ray diffraction and the electronic diffraction, we assign the room-temperature crystalline phase I to orthorhombic sys-tem and P212121 space group with cell parameters of a = 7.43 ?, b = 6.34 ?, c = 72.07 ?, and α = β = γ = 90°. Molecular modeling reveals that the molecules in the unit cell adopt a layered structure with an antiferro-electric alignment. The structure of phase II is very similar to that of phase I. Nonlinear optical measurement shows that m-OSB is active for the second harmonic generation (SHG). Such characteri-zation of the bulk material is necessary for the understand-ing of the growth and microstructures in the films.

The improved performance in the ternary bulk heterojunction solar cells

The ternary blend films have been fabricated via adding 4,4'-N,N'-dicarbazole-biphenyl(CBP,a hole transport material widely used in organic light emitting diodes) into the poly(3-hexylthiophene):[6,6]-phenyl C 61-butyric acid methyl ester(P3HT:PCBM).Despite the wide bandgap(3.1 eV) of the CBP,the solar cell utilizing the optimized P3HT:PCBM:CBP blend film showed an increase of 16% in power conversion efficiency and 25% in short-circuit current than the compared standard P3HT:PCBM blend film.This is attributed to the fact that the addition of the CBP could enhance the aggregation of the P3HT chains and thereby reduce the hole-electron recombination at the interface of P3HT and PCBM.We provide a simple,effective way to improve the performance of P3HT based bulk heterojunction solar cells.

Near infrared electrochromicvariable optical attenuator based on ruthenium complexand polycrystalline tungsten oxide

A near infrared (NIR) electrochromic attenu-ator based on a dinuclear ruthenium complex and polycrys-talline tungsten oxide was fabricated and characterized. The results show that the use of the NIR-absorbing ruthenium complex as a counter electrode material can improve the device performance. By replacing the visible electrochromic ferrocene with the NIR-absorbing ruthenium complex, the optical attenuation at 1550 nm was enhanced from 19.1 to 30.0 dB and color efficiency also increased from 29.2 to 121.2 cm2/C.