Optical absorption bistability in quasi-one-dimensional peierls semiconductors

The optical absorption coefficient γ of a thin film of a Peierls semiconductor has been calculated in the dipole approximation for direct interband transitions as a function of intensity I and central frequency ω₀ of a quasi-monochromatic frequency spectrum near the lower optical transition edge. It is shown that the γ(I, ω₀) dependence is strongly nonlinear, and within a certain region of I and ω₀ variation, not single-valued, which indicates the onset of resonator-free optical bistability with increasing absorption.     

Synthesis of amorphous block copoly(arylene ether ketones) and their characterization

Exchange reactions that may proceed in the course of polycondensation during formation of a polymer from 4,4′-difluorobenzophenone and 4,4′-(isopropylidene)diphenol have been studied. It has been shown that the molecular mass of the polymer decreases under the action of 4,4′-(isopropylidene)diphenol diphenolate. The nucleophilic substitution of the activated aryl halide in DMAA in the presence of potassium carbonate yields high-molecular-mass block copoly(arylene ether ketones) based on 4,4′-difluorobenzophenone and a number of bisphenols. It was demonstrated the synthetic procedure and the chemical structure of block copoly(arylene ether ketones) strongly affect the onset temperature of softening and the mechanical characteristics of the films based on these polymers.     

On the structure of the β-cyclodextrin inclusion complex with 4-acetoxy-1-(2-ethoxyethyl)-4-phenylpiperidine

Russian Chemical Bulletin - Specific features of the structure of the synthesized inclusion complex of 4-acetoxy-1-(2ethoxyethyl)-4-phenylpiperidine with β-cyclodextrin were considered. The...     

Wide bandgap OPV polymers based on pyridinonedithiophene unit with efficiency >5%

We report the properties of a new series of wide band gap photovoltaic polymers based on the N-alkyl 2-pyridone dithiophene (PDT) unit. These polymers are effective bulk heterojunction solar cell materials when blended with phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM). They achieve power conversion efficiencies (up to 5.33%) high for polymers having such large bandgaps, ca. 2.0 eV (optical) and 2.5 eV (electrochemical). Grazing incidence wide-angle X-ray scattering (GIWAXS) reveals strong correlations between π–π stacking distance and regularity, polymer backbone planarity, optical absorption maximum energy, and photovoltaic efficiency.