O. N. Efimov

Polytriphenylamine derivatives as materials for hole transporting layers in electroluminescent devices

A novel, high Tg (ca. 185°C) material for hole-transporting layers has been synthesized. Combination with a 1,2,4-triazole derivative yields an effective blue light-emitting device.

New Organic Electroluminescent Materials

ABSTRACT Spectral and electric properties of five new materials for electroluminescent devices are described including materials for emitting layers and a high-Tg hole-transporting material.

Hybrid organic-inorganic light-emitting diodes

We demonstrate the hybrid organic-inorganic LEDs based on GaN and InGaN blue emitters with some organic luminophores providing blue, green, red and white emission colors with high luminous efficiency. The color of the emitted light from the GaN-based LED can be changed by varying the current through the device due to change in the relation between the UV and visible components of GaN electroluminescence.

Electronic excitation energy transfer in solid solution of 7-diethylamino-3,4-benzophenoxazine-2-one (Nile Red dye) in bis[N-2-(oxybenzylidene)-4-tert-butylaniline]zinc

Transfer of electronic excitation energy from the host material to guest molecules was studied taking the solid-phase system bis[N-(2-oxybenzylidene)-4-tert-butylaniline]zinc + 7-diethylamino-3,4-benzophenoxazine-2-one (the guest compound) as an example. The luminescence excitation spectra and the concentration quenching of green fluorescence of the host compound and the excitation of sensitized red fluorescence of the guest molecules were studied. Among the exciton mechanism of energy migration and Försters long-range, single-jump mechanism, the former dominates. The number of jumps (m) and the mean diffusion length of the singlet exciton (l), calculated in the framework of the model of partially delocalized, randomly hopping exciton, were estimated at ≈1.5·103 and ≈450 Å, respectively.

The composites of polyaniline with multiwall carbon nanotubes: Preparation, electrochemical properties, and conductivity

Composite materials based on the multiwall nanotubes (content in the material from 1 to 65 wt %) and polyaniline are prepared and characterized. The composite materials are prepared by four methods: chemical synthesis, electrochemical synthesis, mixing of dry components, and mixing of solutions with subsequent removal of solvent. The results of calculations of the specific capacity of the composite materials, as well as their conductivity, stability, and behavior under the conditions of charging-discharging point out to their applicability in devices for the energy storage. The range of critical changes in the values of specific capacity and conductivity falls into the interval of the multiwall nanotubes content in the composite from 5 to 25 wt %. The composite materials preparation methods used in this work enable one to choose an appropriate composite preparation method reasoning from the final purpose of its application (obtaining of high capacity or conductivity). The carbon nanotubes, the body of the composite, with their stable electronic conduction, can sustain the composite’s electrical conductivity at reasonable level irrespective of the properties of the second component (polyaniline) in the case in question.

Electronic Excitation Energy Transfer in a Novel Organic Electroluminescent Material

Abstract A new red light-emitting electroluminescent material of the dopant-host scheme is reported. A novel green light-emitting metal complex bis-(2-oxybenzylidene-4-tert-buty-laniline)zinc(II), Zn(OBBA)2, is used as a host material and Nile Red (NR) is used as a dopant. Evidences of the effective electronic excitation energy transfer from host to guest molecules are found. Exciton diffusion and single-step transfer are discussed as possible transfer mechanisms; the former process is considered to prevail in this system.

Two types of retarded charge in the electron-conducting thiophene polymers

A study of the cathodic and anodic doping of polybithiophene and poly-3-phenylthiophene in acetonitrile and propylene carbonate demonstrates that the main fractions of charges of either sign undergo quasireversible redox conversions. Two types of retarded processes reveal themselves. One is associated with conversions of residual portions of positive and negative doping charges trapped in the nonconducting matrix of a neutral polymer at final stages of the undoping process. The other is due to redox conversions of polymer chemically modified when interacting with solution components.

The new composites, polyacetylene-carbon nanotubes: Electrochemical properties

Polyacetylene- and carbon-nanotube-based composite materials are prepared by the method of polymerization filling for the first time. It is shown that the acetylene polymerization mainly occurs at catalytic centers attached to the carbon nanotubes. It follows from TEM data that in the case of single-wall nanotubes the polyacetylene fibriles are wound up onto the nanotubes. In the case of multi-wall nanotubes, polyacetylene can form separate bodies that are connected to the multi-wall nanotubes. The specific electrochemical capacity of the novel composite materials is nearly twice as large as compared with that of the composite prepared by mechanical mixing; it is by two orders of magnitude larger than the pure polyacetylene capacity. The reversibility of the Li+ intercalation-deintercalation electrode reaction appears significantly improved at the polyacetylene-carbon nanotubes composites.

New solid polymer electrolytes based on polyester diacrylate for lithium power sources

New solid polymer electrolytes are developed for a lithium power source used at the temperatures up to 100°C. Polyester diacrylate (PEDA) based on oligohydroxyethylacrylate and its block copolymers with polyethylene glycol were offered for polymer matrix formation. The salt used was LiClO4. The ionic conductivity of electrolytes was measured in the range of 20 to 100°C using the electrochemical impedance method. It is shown that the maximum conductivity in the whole temperature range is characteristic of the electrolyte based on the PEDA copolymer and polyethylene glycol condensation product (2.8 × 10−6 S cm−1 at 20°C, 1.8 × 10−4 S cm−1 at 95°C).

Effect of solvents on properties of polymer gel-electrolyte based on polyester diacrylate

New polymer gel electrolytes based on polyester diacrylates and LiClO4 salt solutions in organic solvents are developed for lithium ion and lithium polymer batteries with a high ionic conductivity up to 2.7 × 10−3 Ohm−1cm−1 at the room temperature. To choose the optimum liquid electrolyte composition, the dependence is studied of physico-chemical parameters of new gel electrolytes on the composition of the mixture of aprotic organic solvents: ethylene carbonate, propylene carbonate, and λ-butyrolacton. The bulk conductivity of gel electrolytes and exchange currents at the gel electrolyte/Li interface are studied using the electrochemical impedance method in symmetrical cells with two Li electrodes. The glass transition temperature and gel homogeneity are determined using the method of differential scanning calorimetry. It is found that the optimum mixture is that of propylene carbonate and λ-butyrolacton, in which a homogeneous polymer gel is formed in a wide temperature range of −150 to +50°C.