S. L. Studzinsky

Information media based on electron donor oligomers with different structures

Information properties of recording media for photothermoplastic techniques were investigated. The films consisted of oligomer composites based on carbazole containing co-oligomers of linear and radial structures with branching centers on silicon and germanium atoms. It was ascertained that the media based on the radial oligomers possessed high holographic sensitivity because of the high plasticity and its ability to accumulate volume electric charge during the exposure. Examples of practical applications of the investigated recording media are presented.

Reversible holographic recording media based on polymeric composites and their use in energy-saving technologies.

The principle of the photothermoplastic method of hologram recording and the general requirements for photothermoplastic holographic recording media based on photoconductive polymer films are considered. The holographic recording media obtained by the authors based on carbazolyl- and ferrocenyl-containing oligomers doped with respective squarillium or merocyanine dyes are discussed. Some examples of practical application of such media in holographic interferometry are demonstrated.

Photoelectric Properties of Photoconducting Composites Based on Non-Photoconducting Polymers Doped by Triarylmethane and Xanthene Dyes

The films of polymeric composites based on non-photoconducting polyvinyl alcohol and polystyrene doped by various concentration of xanthene and triarylmethane type dyes have been prepared. Their photophysical, electrical, and spectral properties have been investigated. It was shown, that all studied composite films exhibit photovoltaic properties and anomalous negative photoconductivity effect. The diffusion nature of observed photovoltaic effect was established. The features of photovoltaic effect and photoconductivity, as well as the possible negative photoconductivity mechanism are discussed.

Effect of concentration of anionic polymethine dye in poly-N-epoxypropylcarbazole polymer film composite on the spectral-luminescent properties and photoconductivity.

The absorption, fluorescence and fluorescence excitation spectra of polymer thin film composites based on poly-N-epoxypropylcarbazole (PEPC) doped with different content of anionic polymethine dye testify to the formation of contact ion-pair associates at high concentration of the latter. The photoconductivity of such composites in the visible spectrum region is observed, despite the absence in the polymer of any fragment capable of accepting a photoexcited electron from anionic dye chromophore. Analysis of the spectral data together with DFT/B3LYP quantum-chemical calculation of the HOMO and LUMO energies of the monomer N-methylcarbazole unit and the radical of the polymethine dye allowed us to suggest the possible mechanism of internal photoeffect in the investigated composites which is based on the formation of the contact ion-pair associates.

Sensitization of Photosemiconducting Properties of Holographic Recording Media Based on Glycidylcarbazole Cooligomers by Organic Dyes

Photophysical and information properties of the holographic recording media (HRM) based on films of ferrocenyl-containing siloxane oligomer, glycidylcarbazole-butylglycidylic ether cooligomer, ferrocenemethylated oligoglycidylcarbazole, and cooligomer of o-carboxybenzoilferrocene glycidylic ether doped with squarilic dye and(or) with merocyanine dye based on ferrocene and tetranitrofluorene are investigated. It is found that the holographic sensitivity is absent for the media based on ferrocenyl-containing siloxane oligomer, and that the holographic sensitivity is present for the films based on glycidylcarbazole. It has been found that the holographic sensitivity and the photoconductivity of the media based on glycidylcarbazole cooligomers increases with the ferrocene content. This effect has been explained by the influence of iron ions on the rate of singlet–triplet conversion in photogenerated pairs of charges.

Photoconductivity of Polymeric Composites Doped with Porous Silicon Nanoparticles and Additions of Ionic Polymethine Dyes of Different Types

Features of the electrical conductivity and the photoconductivity of polyvinylbutyral films containing silicon nanoparticles and similar films doped with cationic and anionic polymethine dyes are studied. Sensitization of the photoelectric effect by dyes with various ionicities in films is explained by the possible photogeneration of holes and electrons from dye molecules and the intrinsic bipolar conductivity of silicon nanoparticles. It is assumed that the electronic conductivity in silicon nanoparticles is higher as compared with that in nanoparticles with p-type conductivity.

Peculiarities of the photovoltaic properties of films based on photoconducting polymer and organic dye in samples with free surfaces and between electric contacts

Composite films based on a carbazolyl-containing oligomer with polymethine dye additives exhibit a change in the magnitude and sign of the photovoltaic response on the passage from the samples with free surfaces to sandwich structures. It is concluded that the photovoltaic effect in the former case is determined by the diffusion of positive charge carriers possessing higher mobility, while in the latter case this effect is controlled by a significant drift of carriers in the electric field created by different work functions of the charge-collecting electrodes. It is shown that the photovoltaic effect also takes place in a nonphotoconducting polymer (polyvinyl ethylal). However, neither the sign nor magnitude of the effect in this case change on the passage from the samples with free surfaces to sandwich structures.

Donor Oligomer Based Film Heterostructures Doped with Squarilium Organic Dye and their Photoelectric Properties

The new heterostructures comprising a squarylium dye (SQ) film deposited onto a oligo-N-epoxypropylcarbazole (OGC) film have been created, and their photoconducting, photodielectric, and photovoltaic properties have been studied. The OGC/SQ heterostructures exhibit the photodiode properties. It is concluded that the p–n junction in these heterostructures is ensured by the hole character of conductivity in the oligomer and the bipolar conductivity of the deposited dye film.

PHOTOVOLTAIC CHARACTERISTICS OF FILM COMPOSITES BASED ON GLYCIDYLCARBAZOLE COOLIGOMER WITH SYMMETRICAL CATIONIC POLYMETHINE DYES

It was found that film composites based on carbazolyl-containing cooligomer with additions of cationic polymethine dyes exhibit photovoltaic characteristics in the absorption region of the dyes. If the length of the polymethine chain is reduced the value of the photovoltaic response is increased as a result of decrease in the energy of the highest occupied orbital of the dye molecule. In samples of the composite films with free surface area the photovoltaic effect is determined by diffusion of the more mobile positive carriers (the Dember effect) and by their recombination time.

Effect of External Electric Field on Diffraction Efficiency of Polarized Holograms in Films of 4-[(2-Nitrophenyl)Diazenyl]Phenyl Methacrylate Copolymer With Octyl Methacrylate

Holograms with a plane wavefront for parallel and orthogonal orientation of polarization of the light beams were obtained in films of the 4-[(2-nitrophenyl)diazenyl]phenyl methacrylate copolymer with octyl methacrylate, and the effect of an external electric field on their diffraction efficiency was investigated. Two effects from the electric field on the diffraction efficiency of the reconstructed holograms were observed: a fast effect leading to decrease of the diffraction efficiency and a slow effect leading to increase of the diffraction efficiency in the reconstructed holograms. The mechanism of formation of the latent holographic image and the effect of the external electric field on it are due not to the photosemiconducting properties of the films but to optical anisotropy in the isomers of the azobenzene groups and the formation of regular surface relief in the films.