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This report presents the results of investigations carried out for polymer- and low-weight molecular materials prepared in the form of thin films by various methods, namely the thermal vacuum evaporation and chemical vapour deposition. The influence of the technological conditions on the structure, surface morphology, and electronic properties of selected organic thin films, including polyazomethines, phthalocyanines, and perylene derivatives as well as their blends, is discussed from the point of view of the potential applications for photovoltaic organic devices.

Potential photovoltaic technology includes the newly developed dye-sensitized solar cells (DSSCs) and bulk heterojunction (BHJ) solar cells. Owing to their diverse qualities, polymers can be employed in third-generation photovoltaic cells to specifically alter their device elements and frameworks. Polymers containing phenothiazine, either as a part of their structure or as a dopant, are easy and economical to synthesize, are soluble in common organic solvents, and have the potential to acquire desired electrochemical and photophysical properties by mere tuning of their chemical structures. Such polymers have therefore been used either as photosensitizers in dye-sensitized solar cells, where they have produced power conversion efficiency (PCE) values as high as 5.30%, or as donor or acceptor materials in bulk heterojunction solar cells. Furthermore, they have been employed to prepare liquid-free polymer electrolytes for dye-sensitized and bulk heterojunction solar cells, producing a PCE of 8.5% in the case of DSSCs. This paper reviews and analyzes almost all research works published to date on phenothiazine-based polymers and their uses in dye-sensitized and bulk heterojunction solar cells. The impacts of their structure and molecular weight and the amount when used as a dopant in other polymers on the absorption, photoluminescence, energy levels of frontier orbitals, and, finally, photovoltaic parameters are reviewed. The advantages of phenothiazine polymers for solar cells, the difficulties in their actual implementation and potential remedies are also evaluated.

In this study, an organic bulk heterojunction (BHJ) solar cell with a spiro OMeTAD as a hole transport layer (HTL) and a PDINO as an electron transport layer (ETL) was simulated through the one-dimensional solar capacitance simulator (SCAPS-1D) software to examine the performance of this type of organic polymer thin-film solar cell. As an active layer, a blend of polymer donor PBDB-T and non-fullerene acceptor ITIC-OE was used. Numerical simulation was performed by varying the thickness of the HTL and the active layer. Firstly, the HTL layer thickness was optimized to 50 nm; after that, the active-layer thickness was varied up to 80 nm. The results of these simulations demonstrated that the HTL thickness has rather little impact on efficiency while the active-layer thickness improves efficiency significantly. The temperature effect on the performance of the solar cells was considered by simulations performed for temperatures from 300 to 400 K; the efficiency of the solar cell decreased with increasing temperature. Generally, polymer films are usually full of traps and defects; the density of the defect (N t ) value was also introduced to the simulation, and it was confirmed that with the increase in defect density (N t ), the efficiency of the solar cell decreases. After thickness, temperature and defect density optimization, a reflective coating was also applied to the cell. It turned out that by introducing the reflective coating to the back side of the solar cell, the efficiency increased by 2.5%. Additionally, the positive effects of HTL and ETL doping on the efficiency of this type of solar cells were demonstrated.

The shielding and spectroscopic properties of Pr +3 and Pr 3+ /Ho 3+ -codoped tellurite glass were investigated. The intensity parameters (Ω2 = 3.24-, Ω4 = 1.64-, Ω6 = 1.10 × 10 -20 cm 2 ) as well as the radiative lifetimes of 3 F 4 + 5 S 2 and 5 I 6 excited states of Ho 3+ ions were equal to 301 μs and 3.0 μs, respectively. The former value appears to be much higher than that obtained from the lifetime measurement, indicating the presence of various energy transfer processes. The NIR spectrum of Pr 3+ /Ho 3+ -co-doped tellurite glass is dominated by strong Ho 3+ : 5 I 6 emission at around 1200 nm, being the result of the energy transfer from Pr 3+ to Ho 3+ ions. The shielding effectiveness of the prepared glasses showed good performance against high-energy photons. These findings suggest that the prepared glasses could be used in laser technology such as photodynamic therapy (PDT) treatment procedures and as shielding for radiation protection.

Third-generation solar cells, including dye-sensitized solar cells, bulk-heterojunction solar cells, and perovskite solar cells, are being intensively researched to obtain high efficiencies in converting solar energy into electricity. However, it is also important to note their stability over time and the devices' thermal or operating temperature range. Today's widely used polymeric materials are also used at various stages of the preparation of the complete device-it is worth mentioning that in dye-sensitized solar cells, suitable polymers can be used as flexible substrates counter-electrodes, gel electrolytes, and even dyes. In the case of bulk-heterojunction solar cells, they are used primarily as donor materials; however, there are reports in the literature of their use as acceptors. In perovskite devices, they are used as additives to improve the morphology of the perovskite, mainly as hole transport materials and also as additives to electron transport layers. Polymers, thanks to their numerous advantages, such as the possibility of practically any modification of their chemical structure and thus their physical and chemical properties, are increasingly used in devices that convert solar radiation into electrical energy, which is presented in this paper.

Optical and structural properties of a blend thin film of (1:1 wt.) of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) doped with iodine (I 2 ) and then exposed to a stepwise heating were reported and compared with the properties of doped P3HT films. The UV-Vis( T ) absorption measurements were performed in situ during annealing runs, at the precisely defined temperatures, in a range of 20-210 °C. It was demonstrated that this new method allows one to observe the changes of absorption spectra, connected with the iodine release and other structural processes upon annealing. In addition, the thermally-induced changes of the exciton bandwidth ( W ) and the absorption edge parameters, i.e., the energy gap ( E G ) and the Urbach energy ( E U ) were discussed in the context of different length of conjugation and the structural disorder in polymers and blends films. During annealing, several stages were distinguished and related to the following processes as: the iodine escape and an increase in P3HT crystallinity, the orderly stacking of polymer chains, the thermally inducted structural defects and the phase separation caused by an aggregation of PCBM in the polymer matrix. Moreover, the detailed X-ray diffraction studies, performed for P3HT and P3HT:PCBM films, before and after doping and then after their thermal treatment, allowed us to consider the structural changes of polymer and blend films. The effect of iodine content and the annealing process on the bulk heterojunction (BHJ) solar cells parameters was checked, by the impedance spectroscopy (IS) measurements and the J-V characteristics registration. All of the investigated P3HT:PCBM blend films showed the photovoltaic effect; the increase in power conversion efficiency (PCE) upon iodine doping was demonstrated.

Three polyazomethines and their corresponding model compounds were protonated with trifluoroacetic acid, and its effect on their optical (UV-vis absorption and photoluminescence) properties and electrochemical behavior has been studied, in the context of the presence and elongation of alkoxy side groups. Moreover, the effect of environment dielectric constants (i.e., polarity of the solvent) was considered on the doping process. It has been proven that the presence of alkoxy side groups is necessary for protonation to occur, while unsubstituted compounds undergo hydrolysis to constitutive units. Acid doping of imines consisting of alkoxy side chains has resulted in a distinct bathochromic shift (>200 nm) of the low-energy absorption band. Even the length of alkyl chains has not affected the position of shifted bands; it has been observed that azomethines with smaller, methoxy side groups undergo the protonation process much faster than their octyloxy-substituted analogues, due to the absence of steric hindrance. The electrochemical studies of these alkoxy-substituted imines have indicated a better p-type behavior after protonation induced by the capability of the protonated form to easily oxidize in acetonitrile and to generate the native molecules. The environmental polarity has also had impact on the doping process, which took place only in low-polar media.

Three novel conjugated polyazomethines have been obtained by polycondensation of diamines consisting of the diimine system, with either 2,5-bis(octyloxy)terephthalaldehyde or 9-(2-ethylhexyl)carbazole-3,6-dicarboxaldehyde. Partial replacement of bulky solubilizing substituents with the smaller side groups has allowed to investigate the effect of supramolecular organization. All obtained compounds have been subsequently identified using the NMR and FTIR spectroscopies and characterized by the thermogravimetric analysis, differential scanning calorimetry, cyclic voltammetry, UV-Vis spectroscopy, and X-ray diffraction. Investigated polymers have shown a good thermal stability and high glass transition temperatures. X-ray measurements have proven that partial replacement of octyloxy side chains with smaller methoxy groups induced a better planarization of macromolecule. Such modification has tuned the LUMO level of this molecule and caused a bathochromic shift of the lowest energy absorption band. On the contrary, imines consisting of N-ethylhexyl substituted carbazole units have not been so clearly affected by alkyl chain length modification. Photovoltaic activity of imines (acting as a donor) in bulk-heterojunction systems has been observed for almost all studied compounds, blended with the fullerene derivative (PCBM) in various weight ratios.

In this paper, we present research on thermal transition temperature determination in poly (3-hexylthiophene-2,5-diyl) (P3HT), [6,6]-phenyl-C61-butyric acid methyl ester (PC60BM), and their blends, which are materials that are conventionally used in organic optoelectronics. Here, for the first time the results of electrical resistance measurements are explored to detect thermal transitions temperatures, such as glass transition T g and cold crystallization T cc of the film. To confirm these results, the variable-temperature spectroscopic ellipsometry studies of the same samples were performed. The thermal transitions temperatures obtained with electrical measurements are well suited to phase diagram, constructed on the basis of ellipsometry in our previous work. The data presented here prove that electrical resistance measurements alone are sufficient for qualitative thermal analysis, which lead to the identification of characteristic temperatures in P3HT:PC60BM films. Based on the carried studies, it can be expected that the determination of thermal transition temperatures by means of electrical resistance measurements will also apply to other semi-conducting polymer films., Competing Interests: The authors declare no conflict of interest.

In this work we present an in-depth study of the how the composition of poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) blend films influences their phase transitions using variable-temperature spectroscopic ellipsometry. We demonstrate that this non-destructive method is a very sensitive optical technique to investigate the phase transitions and to determine the glass transition temperatures and melting crystallization points of the P3HT:PCBM blend films. By analyzing the influence of the temperature T on the raw ellipsometric data, we have identified a high sensitivity of the ellipsometric angle Δ at a wavelength of 280 nm to temperature changes. Characteristic temperatures determined from the slope changes of the Δ( T ) plot appeared to be very good guess values for the phase transition temperatures.