Results 1 - 10 of 10237
Results 1 - 10 of 10237. Search took: 0.03 seconds
|Sort by: date | relevance|
[en] Comparatively recent theoretical and experimental research, which indicates the possible existence of electronic objects with a charge equal to a fraction of the electron charge (e/2, e/3, etc.), is briefly reviewed. (letters to the editors)
[en] It was found that because of the chaotic arrangement of dipoles in ferroelectric semiconductors TlGaS2 and TlGaSe2, the value of the injection current is equal to the maximum. If the samples are placed in an electric field, the dipoles are oriented in the direction of the field. The injection current gradually decreases. When the dipole is placed in the direction of the field, the value of the injection current is equal to the minimum.
[en] Highlights: • New 4,4′-bipyridine derivatives C-substituted with bithiophene groups were prepared. • Their polymerisation afforded novel polymers with 4,4′bipyridine and viologen groups in the main chain. • Conjugation disruption in 4,4′-bipyridine copolymers stabilises doping induced polarons. • 4,4′-bipyridine copolymer chain topology promotes intermolecular π-π interactions. • The viologen repeating unit copolymer demonstrates strong charge trapping/detrapping effects. - Abstract: First report of π-conjugated push-pull copolymer systems with 4,4′-bipyridine moieties in the main macromolecular chain is presented. C-substitution pattern of electropolymerisable bithiophene pendants at the 4,4′-bipyridine unit offered the versatility to retain the latter as free amine, or convert it into bipyridylium salt. Both structures have been prepared and investigated, delivering the first example of a polymer with viologen unit making up the extended π-bond. Detailed electrochemical, spectroelectrochemical and quantum chemical study of these new polymer systems and their 2,2′-bipyridine analogues has shown that while linear structure and extended conjugation in the latter help it to accommodate charge carriers characteristic for heavily doped polythiophene, the conjugation break afforded by the meta substitution pattern across the 4,4′-pirydyl unit makes the polymer behave like an ensemble of shorter oligomeric segments with better defined electron transitions and sharper, and faster electrochromic response. Effective π-π interchain coupling between α,ω-bis(2-pyridyl)quaterthiophene repeating units was observed, whereas intramolecular interactions were found to dominate in the linear 2,2′-bipyridyl based polymer. While the bithiophene derivative of methyl viologen electropolymerised less easily than its corresponding non-quaternised derivative, the resulting polymer films demonstrated decent stability when subject to subsequent p- and n-doping, featuring pronounced charge trapping/detrapping signatures. Furthermore, ion pairing between the viologen and weakly basic PF_6"− and CF_3SO_3"− counterions has been found to impact the redox chemistry of bithiophene functionalised viologen structure. Experimental findings have been confronted with results of quantum chemical computations helping to elucidate the electrochemical and spectroelectrochemical observations made. Presented study delivers insights into the doping processes taking place in conjugation disrupted 4,4'-bipyridine core copolymers, helping to evaluate their potential as substrates for new tuneable π-conjugated polymeric systems.
[en] Highlights: • A formula to describe the field-dependent interface recombination velocity for organic-inorganic heterojunction has been derived. • The recombination of charge carriers is considered in the presence of image force Schottky barrier. • The model is a generalization of the Scott-Malliaras model of surface recombination at the organic/metal interface. We have derived an analytical formula which describes the field–dependent interface recombination velocity for the boundary of two materials characterized by different permittivities. The interface recombination of charge carriers has been considered in the presence of image force Schottky barrier. We suggest that this effect may play an important role in the loss of current for organic–inorganic hybrid heterojunctions. It has been proved that the presented method is a generalization of the Scott–Malliaras model of surface recombination at the organic/metal interface. We also discuss that this model is intuitively similar but not analogous to the Langevin mechanism of bulk recombination.
[en] Both Te inclusions and point defects can trap the charge carriers generated by ionizing particles in CdZnTe (CZT) detectors. The amount of charge trapped by point defects is proportional to the carriers drift time and can be corrected electronically. In the case of Te inclusions, the charge loss depends upon their random locations with respect to the electron cloud. Consequently, inclusions introduce fluctuations in the charge signals, which cannot be easily corrected. In this paper, we describe direct measurements of the cumulative effect of Te inclusions and its influence on the response of CZT detectors of different thicknesses and different sizes and concentrations of Te inclusions. We also discuss a means of partially correcting their adverse effects.