New symmetrical arylene bisimide derivatives formed by using electron-donating–electron-accepting systems were synthesized. They consist of a phthalic diimide or naphthalenediimide core and imine linkages and are end-capped with thiophene, bithiophene, and (ethylenedioxy)thiophene units. Moreover, polymers were obtained from a new diamine, N,N′-bis(5-aminonaphthalenyl)naphthalene-1,4,5,8-dicarboximide and 2,5-thiophenedicarboxaldehyde or 2,2′-bithiophene-5,5′-dicarboxaldehyde. The prepared azomethine diimides exhibited glass-forming properties. The obtained compounds emitted blue light with the emission maximum at 470 nm. The value of the absorption coefficient was determined as a function of the photon energy using spectroscopic ellipsometry. All compounds are electrochemically active and undergo reversible electrochemical reduction and irreversible oxidation processes as was found in cyclic voltammetry and differential pulse voltammetry (DPV) studies. They exhibited a low electrochemically (DPV) calculated energy band gap (Eg) from 1.14 to 1.70 eV. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels and Eg were additionally calculated theoretically by density functional theory at the B3LYP/6-31G(d,p) level. The photovoltaic properties of two model compounds as the active layer in organic solar cells in the configuration indium tin oxide/poly(3,4-(ethylenedioxy)thiophene):poly(styrenesulfonate)/active layer/Al under an illumination of 1.3 mW/cm2 were studied. The device comprising poly(3-hexylthiophene) with the compound end-capped with bithiophene rings showed the highest value of Voc (above 1 V). The conversion efficiency of the fabricated solar cell was in the range of 0.69–0.90%.

In this paper we present results of ellipsometric studies of thin organic poly3hexylthiophene-(P3HT) and poly-3octylthiophene (P3OT) films performed in temperature range 20-300°C. The optical dispersion spectra of refractive and extinction indices of presented organic films was determined in wavelength range 190-1700 nm for temperatures within in a given range. Also thermo-ellipsometric investigations allowed to find temperature dependence on film thickness. The determination of thermal changes of thickness and refractive index allowed us to calculate thermo-optical coefficients (TOC) for P3HT and P3OT layers for many wavelengths in measured spectral range. The obtained values of thermo-optical coefficients of thin P3HT layers, determined from combined ellipsometric and spectro-photometric investigations, are negative in visible part of spectral range of the order of 10 -4 [1/K] .

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We have investigated the spectroscopic properties of Pr3+-doped and Pr3+/Yb3+-codoped tellurite glass with the molar composition 78TeO2–10Nb2O5–5PbO–1PbF2–5Li2O–1La2O3. Analysis of the absorption data has allowed us to calculate the radiative lifetimes of 3P0 excited state of Pr3+ ions and 2F5/2 excited state of Yb3+ ions as being equal to 9.43 and 440 µs, respectively. These values appear to be much higher than those obtained from the lifetime measurements indicating the presence of various energy transfer mechanisms. This conclusion is supported by analysis of the emission spectra obtained for doped glasses under the 445 nm excitation; the visible spectra consist of only Pr3+ transitions, while the near infrared spectrum of Pr3+/Yb3+-codoped glass demonstrates a strong emission from the 2F5/2 excited state of Yb3+ ion around 1000 nm. This emission is a result of the Pr3+–Yb3+ down-conversion energy transfer and its efficiency for our Pr3+/Yb3+-codoped glass is estimated as 29%. For potential applications, it is important to increase this efficiency and further studies are desirable, in particular, an optimal choice of Pr3+ and Yb3+ concentrations to minimize non-radiative energy transfers among the ions through cross-relaxation and energy migration processes.