Marcin Palewicz

Synthesis, materials characterization and opto(electrical) properties of unsymmetrical azomethines with benzothiazole core

Optical (UV-vis and photoluminescence) properties of two soluble organic molecules based on azomethines with benzothiazole core (BTA1 and BTA2) were reported. The structures of both compounds are characterized by means FTIR, (1)H NMR, and (13)C NMR spectroscopy and elemental analysis; the results show an agreement with the proposed structure. The investigated compounds emitted blue light. Influence of excitation wavelength and concentration on maximum and intensity of emission of BTA1 and BTA2 was found. Electrochemical properties of the compounds were studied by differential pulse voltammetry. Introduction of fluorine moieties (BTA1) resulted in lower energy band gap (E(g)) of approximately ∼0.5 eV, whereas BTA2 showed E(g) of ∼2.8 eV. The devices comprised of BTA1 with P3HT:PCBM (1:1:1) showed an open circuit voltage (V(OC)) of 0.40 V, a short circuit current (J(SC)) of 1.19 mA/cm(2), and a fill factor (FF) of 0.23, giving a power-conversion efficiency (PCE) of 0.10% under AM1.5 G irradiation (100 mW/cm(2)).

Opto(electrical) properties of triphenylamine-based polyazomethine and its blend with [6,6]-phenyl C61 butyric acid methyl ester

Polyazomethine (OFBF-TPA) based on triphenylamine (TPA) and octafluorobiphenyl (OFBF) moieties was tested as donor–acceptor (D-A) for bulk heterojunction polymeric solar cells. The temperatures of 5% weight loss (T 5%) of the polyazomethine range from 323 to 328°C, depending on the gas used (air and nitrogen). The conductivity of OFBF-TPA was approximately 10−10 S/cm for not annealed sample and at about 10−6 S/cm for the ones annealed at room temperature, as determined by impedance spectroscopy. Surface of the polymer and mixture polymer–[6,6]-phenyl C61 butyric acid methyl ester (PCBM) was smooth with the R ms value in the range 0.58–1.95 nm as was detected by the atomic force microscopy (AFM) technique. UV-vis spectrum of the mixture OFBF-TPA-PCBM exhibited higher absorption intensity than the UV-vis spectrum of OFBF-TPA lacking PCBM. The thin solid film of OFBF-TPA and OFBF-TPA-PCBM showed one main absorption band with a maximum peak at 414 and 411 nm, respectively. For the mixture OFBF-TPA-PCBM, the second absorption band at 333 nm was found. No influence of annealing on the absorption properties was observed. The polymer solar cell devices were fabricated by spin coating the blend solution of the OFBF-TPA and PCBM and investigated in dark and under an illumination of 100 mW/cm2, with an AM1.5 G. Electrical behavior of the device indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene) (PEDOT)- poly(styrenesulfonate) (PSS)/OFBF-TPA-PCBM/Al was tested by impedance spectroscopy in dark and under illumination. For all measured devices, Nyquist plots were presented. The annealing significantly improved the electrical conductivity of the investigated devices. Electrical and photovoltaic properties of OFBF-TPA were compared with the properties of polyazomethine based on TPA and fluorene moieties (F-TPA).

Thermal and current–voltage behaviour of liquid crystal compounds with rod and bent shapes comprising alkoxysemifluorinated and imine segments

The synthesis and mesomorphic properties of a series of thermotropic liquid crystalline symmetrical rod and bent-shaped imines containing two long alkoxysemifluorinated chains were reported. Three different diamines varying in the number of phenylene rings from 1 to 3 were used to understand structure–mesomorphic property correlation. Differential scanning calorimetry, X-ray diffraction and polarised optical microscopy were used to determine their phase transition behaviour. An enantiotropic smectic phase was observed for all the systems studied. The thermal properties of the azomethines were discussed in relation to the core shape and length of the core. Current–voltage measurements were performed on ITO/compound/Alq3/Al and ITO/TiO2/compound/Alq3/Al devices before and after irradiation with light (about 1000 W m−2). To prepare the TiO2 layer, the sol-gel technique was applied.

Polyazomethine with vinylene and phenantridine moieties in the main chain: Synthesis, characterization, opto(electrical) properties and theoretical calculations

The opto(electrical) properties and theoretical calculations of polyazomethine with vinylene and phenantridine moieties in the main chain were investigated in the present study. 2,5-Bis(hexyloxy)-1,4-bis[(2,5-bis(hexyloxy)-4-formyl-phenylenevinylene]benzene was polymerized in solution with 3,8-diamino-6-phenylphenanthridine (PAZ-PV-Ph). The temperatures of 5% weight loss (T 5%) of the polyazomethine was observed at 356 °C in nitrogen. Electrochemical properties of thin film of the polymer were studied by differential pulse voltammetry. The HOMO level of the PAZ-PV-Ph was at −4.97 eV. The energy band gap (E g) was detected of approximately ∼1.9 eV. Energy band gap (E gopt) was additionally calculated from absorption spectrum and absorption coefficient α. The absorption UV-vis spectra of polyazomethine recorded in solution showed a blue shift in comparison with the solid state. HOMO-LUMO levels and E g were additionally calculated theoretically by density functional theory and molecular simulations of PAZ-PV-Ph are presented. Current density–voltage (J–U) measurements were performed on ITO/PAZ-PV-Ph/Al, ITO/TiO2/PAZ-PV-Ph/Al and ITO/PEDOT/PAZ-PV-Ph:TiO2/Al devices in the dark and during irradiation with light (under illumination of 1000 W m−2). The polymer was tested using AFM technique and roughness (R a, R ms) along with skew and kurtosis are presented.