We report the results of studies of the lasing characteristics of an organic solid-state tunable laser with a polymethylmethacrylate matrix doped with Chromene 3, Pyrromethene 567, and Pyrromethene 597 dyes. The features of lasing when using selective and nonselective cavities are described. Tuning of the laser wavelength with a spectral linewidth of 0.018 nm in the range 550 – 628 nm is obtained on three polymer laser-active media emitting in the yellow and red spectral regions.

Experimental studies of the admittance of MIS structures based on pentacene with a two-layer insulator SiO2–Al2O3 and back contacts made of various materials (Au, Al, In, and Ag) have been carried out in a wide range of frequencies, temperatures, and biases. The concentration of holes in the organic pentacene film found from the capacitance-voltage characteristics took rather high values (in the range (4–40) · 1017 cm–3). The magnitude of the hysteresis of electrophysical characteristics turned out to be minimal for structures with Ag and In back contacts. Significant hysteresis was found for structures with back contacts made of Au and Al at 300 K. For the structure with an Al back contact, a maximum capacitance was observed at the forward voltage sweep in weak accumulation mode, which can be associated with the recharge of the surface state level at the interface between the inorganic insulator and pentacene. An equivalent circuit of a pentacene-based MIS structure is proposed, which allows one to calculate the frequency dependences of the impedance under various conditions. The values of the equivalent circuit elements are found at various biases and temperatures. For structures with back contacts made of Au and Ag, maxima in the temperature dependences of the conductivity associated with the recharge of bulk traps in the organic pentacene film were found.

The features of spontaneous and stimulated emission of polyfluorenes, polyvinylcarbazole, and low-molecular-weight electron-donor compounds incorporated into various materials are studied in the presence of nitrotoluene vapour. Lasing in planar thin-film waveguides is achieved. The dynamics of the lasing spectra of a thin-film optical chemical sensor is presented. It is shown that the response time of the sensor in the lasing regime is 30 s before the lasing intensity decreases by 50% from the initial level.

Spectral characteristics and luminescence under the photo- and electro-excitation of substituted dibenzthiophene sulfone and phenanthridine were studied in this paper. Diphenylamines are substituents introduced in the 2nd and 7th positions (linear configuration) or the 3rd and 6th positions (angular configuration) of dibenzthiophene sulfone or phenanthridine. All molecules show delayed fluorescence, both in solutions and films produced by thermal vacuum deposition. The value of the energy gap between the S1 and T1 states has been estimated and is shown to depend not only on the spatial arrangement of the fragments among themselves (linear or angular), but also on the nature of the substituent in diphenylamine. The highest electroluminescence brightness was found for the molecules, in which triplet levels are involved, both through the process of triplet–triplet annihilation and through thermally activated delayed fluorescence.

The results of studying the influence of copper phthalocyanine (CuPc) nanostructures on the generation and transfer of charge carriers in the semiconductor polymer poly-(3hexylthiophene) (P3HT) are presented. It is shown that the observed broadening and shift of maxima in the absorption spectra of P3HT upon the addition of nanostructures to the polymer are associated with an increase in the film crystallization degree. The observed increase in the short-circuit current and negative magnetic effect upon the addition of CuPc nanostructures is associated with the size effects.

In this study, the influence of the annealing conditions on the formation of macrosteps on the anthracene single crystal surface is demonstrated. Under normal conditions (room temperature, atmosphere pressure, and ambient light), the anthracene surface etching proceeds in two stages: formation of macrosteps with widths up to 15 μm and heights up to 200 nm and formation of pinning centers with heights exceeding 300 nm and widths up to 3 μm. Ambient light with wavelengths in the ultraviolet (UV) range causes the formation of pinning centers on the anthracene surface. In this case, no macrosteps are formed during annealing. In the absence of ambient light, terraces with widths larger than 50μm are formed on the anthracene surface without pinning centers.

The organic light‐emitting device (OLED) structures based on layer (2,8‐bis[N,N‐di(4 methoxyphenyl)amino]dibenzothiophene‐S,S‐dioxide) with thermally activated delayed fluorescence (TADF) are created. The properties of TADF‐based structures are studied by measuring the impedance under various conditions (100 Hz–2 MHz and 10–300 K). The features of the capacitance–voltage curves of the studied structures can be explained by the simultaneous injection of holes from the anode and electrons from the cathode. Cole–Cole plots are studied at various voltages and temperatures. It is shown that at forward bias voltages, the impedance is determined by single relaxation process and at low voltages by more than one process. An OLED equivalent circuit consisting of four serial capacitance–resistance (CR) chains (CR–CR–CR–CR) is proposed. Using this circuit allows us to achieve good agreement between the calculated and experimental frequency dependences of the impedance at various voltages. The different elements of the equivalent circuit are associated with different layers in a multilayer OLED structure. The dependences of the CR element values on the bias voltage are found, and the thicknesses of the corresponding layers are determined.

The results of spectral and luminescent study of zinc and magnesium metal complexes are presented. It is shown that radiation in mixed ligand complexes has the charge transfer character, thereby causing a low oscillator strength, large Stokes shift, and high sensitivity to the environment. These complexes are stable in the solid state, but dissociate in solutions at low concentrations.

Aligned organic thin films with polarized luminescence are obtained by means of the slow vapor deposition of fluorescent blue emitting organic liquid crystalline dipolar molecules, 4-( n -penthyl)-3-chloro-4‴-trifluoromethoxy-[1,1ʹ,4ʹ,1ʺ,4ʺ,1‴-quaterphenyl] (M-BLUE), and red emitting molecules, 4-(dicyanomethylene)-2-(4-amylcyclohexyl)-6[4-(dimethylaminostyryl)]-4H-pyran molecule (M-RED), on the surface of the rubbed conducting polymer (PEDOT:PSS). The polarization degree of M-BLUE thin film was found to be 31%, and for M-RED it is 48%. Essential luminescence quenching by PEDOT:PSS was observed. Strong blue shift of M-RED luminescence on PEDOT:PSS substrate is caused probably because of strong interaction between these counterparts.

Sensor properties of poly(9,9-di-n-octyl-2,7-fluorene) (PFO), poly[9,9-dioctylfluorenyl-2,7-diyl] end capped with dimethylphenyl (ADS), polyvinylcarbazole (PVK), N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]4,4′-diamine (TPD), and 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPD) on the presence of nitrotoluene vapor are studied. Sensor properties of fluorophores doped into different materials are investigated using the method of fluorescence quenching due to formation of the non-fluorescent complex between the fluorophore and nitrotoluene molecules.

In a wide range of frequencies and temperatures, the admittance of MIS structures based on pentacene organic films, formed by thermal evaporation in vacuum on SiO 2 and SiO 2 /Ga 2 O 3 substrates, was experimentally investigated. The capacitance-voltage characteristics of MIS structures with a SiO 2 insulator have virtually no hysteresis. It is shown that at temperatures of 150–300 K, an inversion layer is formed in the structures at large positive bias voltages. The concentration of holes in pentacene, determined from the capacitive measurements, exceeds 10 18 cm –3 and is practically independent of temperature and frequency. The experimental frequency dependences of the admittance of MIS structures with the SiO 2 insulator are in good agreement with the results of calculations performed using the method of equivalent circuits. For structures with a Ga 2 O 3 layer, the negative differential conductance of the insulating layer was detected, which requires the complication of the equivalent circuit. The possibility of using the low-temperature admittance measurements for studying the traps in the pentacene film bulk is shown.

Pentacene-based metal-insulator-semiconductor capacitors with SiO2 and SiO2/Ga2O3 insulators were investigated in the temperature range of 9-300 K. The capacitance-voltage curves of the fabricated capacitors had virtually no hysteresis when using SiO2 as an insulator. The hole concentration values, determined using the Mott-Schottky analysis, were in the range of (1.0-1.3) x 10(18) cm(-3), depending on the substrate used. It is shown that the hole concentration remains constant over a wide range of frequencies and temperatures. It is shown that the type of the substrate (SiO2 and SiO2/Ga2O3) significantly affects the electrical characteristics of pentacene MIS capacitors. A pentacene film grown on SiO2 substrate was found to have a shallow level with activation energy of about 3 meV. For the case of using SiO2/Ga2O3 substrate, trap levels with activation energies of (5.5-6.0) and (480-570) meV were revealed.

In this work, the effect of formation of macrosteps under dissolution of the anthracene single crystal surface is shown for the first time. Under standard conditions (room temperature, atmospheric pressure, natural illumination), the etching process of the anthracene single crystal surface can be divided into two stages: formation of macrosteps up to 15 μm in width and 200 nm in height and formation of the step inhibition centers more than 300 nm in height and up to 3 μm in width. The second stage leads to a significant increase in the surface roughness due to the formation of a wave-like relief.

The current-voltage characteristics and admittance of multilayer structures for organic LEDs based on the PEDOT:PSS/NPD/YAK-203/BCP system have been experimentally investigated in a wide range of the measurement conditions. It is shown that at voltages corresponding to the effective radiative recombination of charge carriers, a significant decrease in the differential capacitance of the structures is observed. The frequency dependences of the normalized conductance of LED structures are in good agreement with the results of numerical simulation in the framework of the equivalent circuit method. Changes in the frequency dependences of the admittance with a change in temperature are most pronounced in the temperature range of 200–300 K and less noticeable in the temperature range of 8–200 K. From the frequency dependences of the imaginary part of impedance, the charge carrier mobilities are found at various voltages and temperatures. The mobility values obtained by this method are somewhat lower than those determined by the transient electroluminescence method. The dependence of the mobility on the electric field is well approximated by a linear function. As the temperature decreases from 300 to 220 K, the mobility decreases several times.

The photophysical properties are calculated for the dibenzothiophene sulfone substituted with various electron donor moieties:3,7-bis[N,N-di(4-tert-butylphenyl)amino]dibenzothiophene-S,S-dioxide (1L), 2,8-bis[N,N-di(4-tert-butylphenyl)amino]dibenzothiophene-S,S-dioxide (1A), and 2,8-bis[N,N-di(4 methoxyphenyl)amino]dibenzothiophene-S,S-dioxide (2A). It is shown that the linear arrangement of the electron donor substituents relative to the dibenzothiophene sulfone acceptor turns compound (1L) an efficient prompt fluorescent emitter, while the angular arrangement of the substituents decreases the efficiency of prompt fluorescence, but increases the efficiency of thermally activated delayed fluorescence (TADF). Replacing the auxiliary tert-butyl groups in the donor moieties by methoxy groups leads to an increase in k(ISC) and k(RISC). OLEDs are made with the studied compounds.

Results of theoretical and experimental studies of exciplex of a zinc complex Zn(DFP-SAMQ) 2 with the hole-transporting layer of NPD are presented. It is shown that at least three different arrangements of Zn(DFP-SAMQ) 2 and NPD molecules in the excited state result in the long-wavelength charge-transfer emission bands. At the same time, such systems are unstable in the ground state.

An approach to inkjet printing of low-viscosity liquids is suggested consisting in suppression of undesirable weakly damped acoustic oscillations under the action of a double pulse. The duration and amplitude of the second pulse are adjusted so that the arising acoustic oscillations are in antiphase to those of the first pulse.

Results of investigation of spectral-luminescent and lasing characteristics of substituted 1,3-oxazoles and 1,3,4-oxadiazoles lasing in the blue-green spectral region are presented. For some compounds, efficiencies of 40 and 38% have been achieved with pump power density of 7 MW/cm 2 . A 34 nm wide tuning range in the blue-green spectral region with lasing line width of 0.012 nm is shown. A series of laser-active compounds with good solubility in methyl methacrylate capable of effectively lasing is determined.

Results of investigation of the spectral-luminescent and lasing characteristics of films based on methacrylates doped with pyrromethene 567 lasing in the yellow-green spectral range are presented. It is shown that incorporation of an additional layer, which improves the waveguide properties of the thin-film structure based on polymethylmethacrylate, increases the energy conversion efficiency and substantially reduces in different degrees the lasing threshold of the examined structures equal to 50–250 kW/cm 2 . In the structure with additional layer, an efficiency of 60% comparable to blocks of solid-state laser-active elements of organic lasers is obtained.