Alek R. Tameev

Near-infrared electroluminescence in polymer composites based on organic nanocrystals

IR electroluminescence was revealed in single-layer light-emitting diodes based on a type of electroactive polymer nanocomposites-electron-hole conducting aromatic polyimide and organic nanocrystalline particles of cyanine molecules, known as J-aggregates. These materials exhibit a very narrow emission band with a maximum at 815 nm. Dramatic increase of charge-carrier mobility was observed for these layers containing the J-aggregate nanocrystalline phase.

Aromatic Polyimides as Efficient Materials for Organic Electroluminescent Devices

Derivatives of newly synthesized aromatic polyimides containing sulphur atoms in the backbone were studied as electron-hole-transporting and light-emitting materials for use in combination with tris(8-hydroxyquinoline)-aluminium in multilayer organic electroluminescent devices. Efficient bipolar charge transport has been revealed in the polymers. Bright electroluminescence (15 000 cd m -2 at 14V) was observed in the visible range. The possible role of intermolecular donor-acceptor interactions in the mechanism of electroluminescence is discussed.

Charge carrier transport in polyimides based on 9,10-bis(p-aminophenyl)anthracene

Transient currents were measured by the time-of-flight technique in films of aromatic polyimides based on 9,10-bis(p-aminophenyl)anthracene and a series of diimide fragments. The electric field and temperature dependences of the hole and electron drift mobilities were detected. In amorphous films of the soluble polyimide with a phthalide group in the diimide fragment, the drift mobility was found to reach the value of 10-4cm2V-1s-1 at 5·5×105Vcm-1 and 291K. In the insoluble polyimide films including the crystalline phase, the mobility was lower by one or two orders of magnitude. This is attributed to the presence of cavities in the films of the insoluble polyimides. The applicability of known theoretical models describing temperature and electric field dependences of the drift mobility is discussed.

Charge carrier transport in aromatic polyimides and polyimide/J-aggregate composites

In aromatic polyimides based on 9,10- bis(aminophenyl)anthracene or 9,10- bis(phenylthio)anthracene, charge carrier transport has been studied by conventional time-of-flight techniques. The electric field and temperature dependencies of both hole and electron drift mobility were observed. In amorphous film of the soluble polyimide, the drift mobility was found to reach the value of 10-4cm2V-1s-1. In film of the insoluble polyimide containing a crystalline phase, the mobility was lower by one or two orders of magnitude. The result is attributed to the presence of cavities in the crystalline film. The applicability of known theoretical models describing the temperature and electric field dependencies of mobility is discussed. It was found out that J-aggregates, formed in the soluble polyimides doped with cyanine dye molecules, play an active role in charge carrier transport in the electroluminescence composites.

Influence of transport site alignment on electron and hole mobilities in polymer films

Abstract For doped polymer transport films, it has been experimentally found that electron and hole drift mobilities are decreased when disordered dipole transport molecules are oriented along the external electric field.

Hole drift mobilities in polycarbonate doped with a series of triphenylamine derivatives

Hole drift mobilities (mu) were measured in a series of triphenylamine (TPA) molecules and oligomers dispersed into bisphenol-A polycarbonate (PC) by conventional time-of- flight techniques. The transport molecules were oligomeric triphenylamine (OTPA) containing 8-10 TPA units TPD and TPA. In PC doped with 50 wt percent OTPA, TPD, and TPA, (mu) values were of 1 X 10-7, 1 X 10-5, and 7 X 10-6 cm2/(V S) accordingly, at the electric field of F equals 5

Electron and hole transport in N-picrylarylamine-doped polycarbonate

MUL 105V/cm and room temperature. In order to elucidate the relationship between structure of transport site and mobility, the molecular orbital calculations were made for the TPA, TPD and OTPA molecules. For the calculations, the PM3 method was chosen because it gave better agreement between calculated and experimentally parameters than the AM1 method for the molecules studied. The result obtained from the hole mobility measurements and the quantum chemistry calculations demonstrate that the N-Ph-Ph-N fragment is a transporting center for both TPD and OTPA molecules. For OTPA, the end fragments of the molecule appear as transport sites.

Charge mobility and photovoltaic behaviour of carbocyanine dye layers deposited by thermal evaporation in vacuum

Electron and hole drift mobility in N-picrylarylamine doped polycarbonate films has been studied by the conventional time-of-flight technique. The charge transport molecules contain both electron acceptor and donor functionalities. Electron mobility is similar in value for all the systems as the electron acceptor functionality is the same in all the molecules. Hole mobility depends on the donor functionality. The results can be fit well into a correlated disorder model when energetic features of the transport molecules are also taken into account. For quantum-chemistry calculations, the semiempirical PM3 and ZINDO/S methods were used.