Investigation of Local Trapping States in Organic Molecular Crystals by Method of Thermally Modulated Space-Charge Limited Current

The method of thermally modulated space-charge limited current has been used for studying local charge carrier trapping state energy spectra in vacuum evaporated thin films and Langmuir-Blodgett multilayers of different organic molecular crystals. In case of evaporated thin polycrystalline layers of pentacene four sets of local trapping states in energy range from E$\text{}_{t}$ = 0.35 to 0.06 eV were observed. In evaporated thin layers of dimethylaminobenzylidene indandione-1,3 five sets of trapping states from Ε$\text{}_{t}$ = 0.59 to 0.28 eV were detected. In the evaporated layers of indandione-1,3 pyridinium betaine only a single set of very shallow trapping states close to the conductivity level was observed. In the Langmuir-Blodgett multilayers of vanadyl phthalocyanine and indandione-1,3 pyridinium betaine the activation energy E$\text{}_{a}$ dependence on applied voltage U, E$\text{}_{a}$(U), for bulk conductivity is not step-like as in case of evaporated layers, but of rather complicated, oscillatory shape. Such character of the E$\text{}_{a}$(U) dependence may be explained by the specific quantum well structure of the Langmuir-Biodgett multilayers and spatially nonuniform trap distribution. However, for in-plane conductivity of indandione-1,3 pyridinium betaine films the E$\text{}_{a}$(U) dependence is step-like and two sets of trapping states at E$\text{}_{t}$ = 0.45 ± 0.03 eV and E$\text{}_{t}$ = 0.18 ± 0.03 eV were obtained. In case of bulk conductivity of the Langmuir-Blodgett layers the activation energy E$\text{}_{a}$ at sufficiently high electric fields drops down to zero and the charge carrier transport switches to a "trap-free" regime

Synthesis and Physical Properties of Red Luminescent Glass Forming Pyranylidene and Isophorene Fragment Containing Derivatives

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Object size effect on the contact potential difference measured by scanning Kelvin probe method

Contact potential difference (CPD) was measured by macroscopic Kelvin probe instrument and scanning Kelvin probe microscope on Al, Ni and Pt on ITO substrates at ambient conditions. CPD values measured by scanning Kelvin probe microscope and macroscopic Kelvin probe are close within the error of about 10–30% for large studied objects, whereas scanning Kelvin probe microscope signal decreases, when the object size becomes smaller than 1.4 μm. CPD and electric field signals measured using many-pass technique allowed us to estimate the influence of electrostatic field disturbance, especially, in the case of small objects

Novel Amorphous Red Electroluminescence Material Based on Pyranylidene Indene-1,3-dione Derivative

Research devoted towards studies of the new organic molecules with light-emitting propertie

Novel Amorphous Red Electroluminescence Material Based on Pyranylidene Indene-1,3-dione Derivative

The organic light emitting diode (OLED) is a promising device for future technologies, like flat panel displays and novel light sources. So far the OLED struc-tures have mostly been made by thermal evaporation in vacuum. An alternative approach is to use small molecules which form solid state with glassy structure from solutions. Such compounds can be used in the ink-jet printing technologies and result in reducing the OLED prices. In this paper, we present an original red fluorescent organic compound 2-(2-(4-(bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-4H-pyran-4-ylidene)-1H-indene-1,3(2H)-dione (ZWK1), with the maximum of the photoluminescence spectrum for solid state at 657 nm. The structure of the electroluminescent device was ITO/PEDOT: PSS (40 nm)/ZWK1 (120 nm)/LiF (1 nm)/Al (100 nm). The electroluminescence spectra correspond to the CIE coordinates x = 0.65 and y = 0.34 with the maximum at 667 nm. The power and luminance efficiency at the luminance of 100 cd/m2 is 0.43 lm/W and 1.97 cd/A, respectively

PV and magnetic field effects in poly(3-hexylthiophene)-fullerene cells doped with phthalocyanine soluble derivative

An attempt was made to widen the photosensitivity spectral range of poly(3-hexylthiophene)-fullerene blend by adding an extra electron donor — a newly synthesized soluble phthalocyanine derivative (SnClPc) having the electron absorption band at 708 nm. As the electron acceptor, home-synthesised di(ethoxycarbonyl) methano-fullerene carboxylate (C61(CO2Et)2) was used, and as the hole transporter — the regioregular poly 3-hexylthiophene (P3HT). The sandwich-type samples were prepared on an ITO glass substrate by coating it with a 30–50 nm thick PEDOT:PSS layer followed by a ~100 nm thick P3HT:C61(CO2Et)2:SnClPc blend. For the top electrodes In or Au were used. Spectral dependences of the PV effect and of the influence of external magnetic field (0–3000 Oe) on it were studied in the 370–1000 nm spectral range in vacuum of ~10-6 Torr. Significant photosensitivity of the blend was observed in the 370–800 nm spectral range. However, the short-circuit photocurrent quantum efficiency evaluated for absorbed light was found to be 4 times higher for illumination in the P3HT absorption band as compared with that in the SnClPc band. The observed magnetic field effect shows that the low IPCE values may be explained by the space charge formation in the samples, leading to a strong geminate recombination of CP states