Nikolay Davidenko

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.

Charge flow in polymer films on PEPC base doped by polymethine dyes

Abstract The charge flow mechanism of polymer layers fabricated from polyepoxypropylcarbazol (PEPC) doped with polymethine dyes (PD) was investigated. The I–V characteristics of ITO-PEPC(:PD)-metal structures were studied by electrophysical differential method at room temperature. Various metals were used as a contact (In, Sn, V, Ni, Al, etc.). Injection properties of contacts is shown to depend on work function of electrons from contact material. Changes in charge flow mechanisms and activation energy ionization due to various enhance of dopant concentration are discussed. Electroconductivity of doped layers was enhanced to fivefold with increasing PD concentration from 0.1 to 4%. Increase of polymethine chain length increases the electroconductivity of doped PEPC layers.

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.

Photovoltaic effect in dye-doped polymer films with free-surface and sandwich structures

Photovoltaic properties of the polymer composite films doped with cationic, anionic and neutral polymethine dyes were investigated. It was revealed that the magnitude and even the sign of photovoltaic effect change in going from the free-surface to sandwich structures. It was shown that in free-surface samples the photo-emf sign is determined by the nature of polymer and dye. By contrast, in sandwich structures the photo-emf sign does not depend on composition of the photoactive layer and is governed by drift of the photogenerated charge carriers in the electric field formed by different work function of the electron- and hole-collecting contacts.

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.

Spin-dependent Effects in Charge Photogeneration Mechanism in Amorphous Molecular Semiconductors

Abstract The paper is devoted to the investigation of multiplicity and evolution of multiplicity in the course of life of electron-hole pairs in the films of poly-N-epoxypropylcarbazole, containing the CT-complexes, the compounds with intramolecular charge transfer as the electron-hole pair photogeneration centres. The main results were obtained from the analysis of the effects of external magnetic and electric field influence on photoconductivity.

Peculiarities of Radiative Recombination in Poly-N-epoxypropylcarbazde Doped With Polymethine Dyes

Abstract Processes of charge carrier photogeneration and recombination are investigated in films of poly-N-epoxypropylmbarbazole (PEPC) doped with polymethine dyes. It is presumed, that the cause of growing the recombination luminescence intensity in external electric field is connected with increase of efficiency of radiative recombination stimulated by captured electrons from photogenerated excitons.

Electro-optic properties of novel azobenzene polymers

Polymers containing azobenzene dyes or azobenzene lateral groups are of special interest for their application as optically active media, particularly, as polarization sensitive media for such applications: optical data storage, surface nanostructuration, photoswitching, alignment of liquid crystals, active optical elements etc. An intensive research was carried out previous years on synthesizis and investigation of the second order nonlinear optical response of azobenzene/polymer systems. The desirable properties of these materials are attributed to the highly efficient photoinduced trans-cis and vice versa isomerization of azobenzene moieties. This transformation is connected with the volume change of molecules, followed by an increase of their rotational mobility. The trans-cis izomerization process is exploited also in all optical poling of polymers and plays an important role in optical depoling. Generally these phenomena are induced by light with frequencies corresponding to one-photon absorption. They are possible also by multiphoton absorptions. In this paper we report the synthesis of side chain methacrylic polymers functionalized with azobenzene chromophores. A reversible change of thin film absorption is observed when illuminating it with monochromatic, linearly polarized light under the applied external DC field. The amount of change depends on the angle between the light polarization and the DC electric field direction.

Holographic interferometry imaging monitoring of photodynamic (PDT) reactions in gelatin biophantom

Heat and photochemical reactions with human hemoglobin and photosensitizer were monitored by holography interference method in gelatin phantom. The method has successfully facilitated monitoring the reactions as a highresolution refraction index mapping in real time video regime. Methylene Blue was exploited as a photosensitizer.

Polymer Materials with Organic Dyes of Various Ionic Ability for Photosensitive and Light Emitting Structures

ABSTRACT The peculiarities of charge flow mechanism in polymer films on the PEPC base with organic dyes of various ionic ability were investigated. The electroconductivity was established to depend on dye nature, their ionic ability and content in polymer media. The approximation of the current-voltage characteristics as exponential function was presented and the activation mechanism of charge flow in investigated structures was established. The activation energy of various system was estimated end established to depend on the dye concentration in PEPC. The self-organization as penta- and hexagons and aggregation in investigated structures obtained.