We investigated the photoconducting and photovoltaic properties of thin film composites based on polyN-epoxypropylcarbazole dopped with molecules of two organic conductors, namely, tetrathiаfulvalene and Ni-dithiolene derivatives. It was established that these composites have hole photoconductivity, and the internal photoeffect is determined by the photogeneration of the charge carriers from the added molecules and the charge transport through the donor fragments of the polymeric matrix.

Using luminescent spectroscopy of destruction products at excitation by monochromatic electrons with different energy in the gas phase, it was shown that studied electroactive molecules with approximately the same dimensions and different chemical structure have very different stability under interaction with electrons. All molecule spectra contain luminescence of hydrogen, С 2 and СН, as well as СО, CN, I, Al, Ir in molecules containing these elements or groups. Luminescence of decomposed molecules is observed at electron energy of about 40–50 eV (for the most typical components such as hydrogen in carbazole and aluminium in AlQ 3 ). This testifies that luminescence of fragments is the result of their excitation by electrons. The amount and luminescence intensity of decomposition products are increasing with a growth of temperature and electron energy.

Photoluminescent and electroluminescent properties of four new bipolar linear derivatives of divinyl dibenzothiophene sulfone are studied. It is found that amorphous films of solutions, as well as films of the compounds under study in the poly(N-vinylcarbazole) matrix, have a rather high quantum yield of photoluminescence in the blue and blue-green spectrum regions. Bright blue electroluminescence is obtained in the samples with a structure of ITO/PEDOT:PSS/TPD/OC/LiF/Al using vacuum deposition of the compounds under study and in the single-layer ITO/PEDOT:PSS/PVK:OC/LiF/Al structure when applied from the solution with a threshold voltage of 2.5–3.5 V. The influence of a molecule structure on the spectra and quantum yield of fluorescence as well as on the electroluminescent properties of the compounds is shown. Results of quantum-chemical calculations in the context of the density functional theory of the structure and characteristics of main molecular orbitals are presented.

Electron attachment spectroscopy is employed to demonstrate that the scattering of slow (0–15 eV) electrons from perylenetetracarboxilic dianhydride (PTCDA) molecules in the gas phase leads to the resonant formation of molecular and fragment negative ions detected in the mass-spectrometric experiment. Depending on the electron energy, currents of anions have clearly manifested peaks at 0.14, 1.9, 3.0, 4.8, and 5.7 eV. In addition, resonant states are also detected at thermal energy (0 eV) of scattered electrons, as well as at 0.4 and 1.0 eV, as shoulders on experimental curves. The spectroscopic states of PTCDA anions at energies exceeding 0 eV are interpreted in terms of the formation of shape resonances on the basis of calculated values of energies of π*-type unoccupied molecular orbitals. It is found that the positions of unoccupied orbitals of an isolated PTCDA molecule correspond to the peaks in the density of states of the conduction band of PTCDA films provided that the energies of the orbitals are shifted by 1.4 eV. The latter value can be interpreted as the binding energy of a molecule in the film due to the polarization interaction with the surroundings.

Bound states of electrons with electroactive aromatic molecules, promising for use in molecular electronics, are studied employing electron attachment spectroscopy Anions are produced in the gas phase through the capture of electrons with energies of up to 15 eV by molecules via the resonance mechanism. The possible pathways of fragmentation of molecular anions and the times of electron retention by the test molecules at various incident electron energies are measured. The resonance states identified are interpreted with the help of quantum-chemical calculations. The possibility of applying the results obtained to molecular electronics is discussed.

Single and dissociative ionizations of the POPOP molecule by electron impact in the gas phase are studied using mass spectroscopy. Fragmentation pathways of the molecule are proposed taking into account the common system of conjugated π-electrons and heteroatoms in the POPOP molecule. The appearance thresholds for certain fragments of the molecule are determined based on experimentally measured ionization cross sections as functions of the ionizing electron energy. An ion with m/z = 144 [C9H6ON]+ that is complementary to a fragment with m/z = 220 [C13H10ON]+ (present in the NIST mass spectrum database) is found for the first time in the mass spectrum of POPOP. Its appearance threshold is determined (Eap = 9.48 eV).

From oxygen-induced quenching of polarized fluorescence of 4,4′-bis[2-(1,3-benzoxazol-2-yl)ethenyl]biphenyl, we have observed structural transformation in electronically excited molecules with retention of fluorescent capability, initiated by collisions with oxygen. Replacing two hydrogen atoms with fluorine in the ortho positions of the diphenyl moiety of the molecule leads to absence of quenching upon collisions with oxygen molecules, owing to the electronegative properties of fluorine atoms.

We have studied the effect of the intensity of the exciting radiation and the temperature on the emission properties of two kinds of thin-film samples based on blends of two types of organic electroactive materials: polyfluorene + iridium triphenylpyridinate and polyepoxypropylcarbazole + zero-th order PAMAM dendrimer with eosin. We have shown that an increase in the excitation intensity leads to an increase in the intensity of the luminescence of the polymer matrices and the iridium complex up to a power density of 300 kW/cm 2 , and the emission of the dendrimer is rapidly saturated and does not return to the initial value when the excitation level decreases. Heating up to 170°C followed by cooling causes an increase in the intensity for all the components except the dendrimer. The data obtained show that annealing is an important method for improving the emission efficiency of the proposed thin-film structures, due to a change in the packing of the activator molecules in the polymer matrix leading to more efficient transfer of the excitation energy. Molecules of the studied dendrimer are not stable when exposed to optical radiation and temperature.

We have measured the energy loss spectra of 4,4′-bis[(E)-1-(1,3-benzoxazol-2-yl)-2-ethenyl]-2-n-hexyloxy biphenyl for interaction with electrons with energies 17.5 eV and 50 eV. We used time-dependent density functional theory to calculate spectra of the singlet transitions, which match the experimental data well. We have shown that the cross section for the long-wavelength transitions is greater than the cross section for the short-wave transitions, which is attractive for efficient excitation by low-energy electrons. Electroluminescence was achieved for the studied compound. The threshold voltage was 3.5 V. Introducing an additional layer of copper phthalocyanine increases the brightness of the luminescence several-fold.

The electrical and luminescence properties of a poly(amidoamine) (PAMAM) dendrimer containing naphthalimide are investigated. The influence of adsorbed oxygen on the electrical conductivity of thermally evaporated organic films is analyzed using cyclic thermal desorption. The results obtained are interpreted within a model of two-level hopping electron transfer according to which one of the two systems of energy levels corresponds to intrinsic states of electrons in PAMAM molecules and the other system is associated with the states of electrons in adsorbed oxygen molecules. The use of the cyclic thermal desorption method in combination with the proposed model makes it possible to estimate the localization length of electrons numerically and to determine the states involved in hopping electron transfer. It is demonstrated that the studied compound in the solid state possesses a high luminescence power over a wide spectral range.

Electron energy loss spectra (EELS) of fluorene, fluorenone, and diiodofluorenone vapors excited by monokinetic electrons of energies 15–50 eV have been obtained. The singlet and triplet absorption bands of these molecules have been calculated. Comparison of these bands with the experimental EELSs and optical absorption spectra has shown that the forbiddenness of singlet-triplet transitions is not completely removed in the process of interaction of molecules with electrons. The presence of heavy iodine atoms in the diiodofluorenone molecule enhances singlet-triplet transitions. Bands of overtones of stretching vibrations of the CH groups of the benzene rings have been detected near the peak of elastic scattering of electrons of the molecules studied.

Polarization of the fluorescence of the vapors of anthracene, perylene, 1,4-di(2,5-phenyloxazolyl)benzene (POPOP), and 2-phenyl-5-(4-biphenylyl)oxazole (BPO) upon excitation by a beam of monokinetic electrons with energy varying in the 5–300-eV range has been found. The electrical vector of radiation has a higher value in the direction perpendicular to the direction of the electron beam. For the substances studied, maxima of fluorescence polarization are observed that approximately coincide in position with the maxima of the excitation function. The maximum value of the fluorescence polarization degree of POPOP does not exceed 3.8%.

This paper is a brief review of investigations on the electroluminescence of organic compounds. It considers the background of the problem, the organic electroactive materials, the structures based on them and the technology of their preparation, the main physical characteristics of electroluminescence (spectra, polarization, volt-luminance and volt-ampere characteristics, kinetics, temperature dependence, quenching, efficiency and operation time, and ways of increasing them). A brief analysis of the investigations on injection of charge carriers, their transport, and the formation of excited states of molecules as well as applications and prospects of development of organic electroactive materials and structures is carried out.

The energy‐loss spectra of electrons, fluorescence excitation functions, and the fluorescence spectra on excitation of the vapors of a number of oxazoles and oxadiazoles by monokinetic beams of electrons of various energies are determined. In contrast to optical absorption spectra, in the energy‐loss spectra of a number of studied substances a band associated with the S 0 – T 1 singlet‐triplet transition is observed. The π–π * ‐type transitions are fixed up to S 0 – S 5 on excitation of molecules by high‐energy electrons, including the region of vacuum ultraviolet. The cross sections of elastic and inelastic collisions of electrons of different energies with POPOP molecules have been measured. The dependences obtained differ substantially from those calculated in the Born approximation. The cross section of elastic scattering is in a rather good correspondence with the geometric section of the molecule.

We propose a simple model for describing the electroluminescence in a single-layer thin-film organic electroluminescent cell on the assumption that the luminophore molecules are directly excited by electron impact and are the result of recombination. The calculated luminescence and efficiency curves are in qualitative and quantitative agreement with experimental data. To attain a high efficiency, it is necessary to use cathodes with a low work function and a high Fermi energy and relatively small electric fields.

In the electron energy loss spectra (EELS) of the organic europium complexes Eu 3+ (BTFA) 3 TPPO and Eu 3+ (Br‐BTFA) 3 TPPO in a gas phase obtained on excitation by monokinetic beams of electrons of different energies in the range 12–50 eV, we have identified the bands associated with the electron transitions S 0 – S 1 , S 0 – S 2 , and S 0 – S 3 . The connection of these transitions with the structural groups of the complexes is established. The addition of the bromine atom to the phenyl ring of β‐diketonate leads to the rise in the relative intensity of the S 0 – S 2 band. The singlet‐triplet transitions manifest themselves in the region 2.5–3.2 eV and contribute to the S 0 – S 2 band of the electron energy loss spectra.

This paper analyzes the possibilities of obtaining induced radiation in single‐layer organic electroluminescent structures on the basis of the proposed model of luminophor molecule excitation by “hot” electrons emitted from the cathode as a result of the tunnel effect. Numerical calculations of the kinetic, spectral, and energy characteristics of radiation in the regime of single‐pass superluminescence and in the presence of positive feedback have been made. It has been concluded that, in principle, it is possible to obtain in such systems induced radiation at actually attainable values of the applied electric‐field strength, and the conditions for this have been analyzed.

Experimental data on the synthesis and spectral properties (UV, IR‐Fourier, x‐ray photoelectronic, and luminescence spectra) of the sulfonamide derivative of benzocoumarin in an isopropanol solution and in a film applied by thermal vacuum deposition (TVD film) are reported. The use of TVD films of the investigated substance as electroluminophors is shown to be promising.

The spectra of electron‐energy loss, excitation functions, and fluorescence spectra in excitation of the vapor of polyphenyls and polyacenes by electron beams of different energies are determined. The influence of successive complication of the molecules under study on these spectral‐luminescence characteristics is tracked. Unlike the optical absorption spectra, in the spectra of electron‐energy loss of all the substances studied one observes a band which is related to the singlet‐triplet transition S 0 – T 1 . The transitions up to S 0 – S 5 are recorded in excitation of the molecules by high‐energy electrons, including the region of vacuum ultraviolet. From the functions of fluorescence excitation the authors have determined the excitation thresholds that correlate with the energies of the S 1 levels, except for pyrene in which the S 0 – S 1 transition is forbidden and does not show up not only in photon excitation but also in electron‐beam excitation, although the intercombination forbiddenness in the latter case is removed and the S 0 – T 1 band is observed.