Alexey A. Piryazev

Highly Efficient All-Inorganic Planar Heterojunction Perovskite Solar Cells Produced by Thermal Coevaporation of CsI and PbI2

We report here all inorganic CsPbI3 planar junction perovskite solar cells fabricated by thermal coevaporation of CsI and PbI2 precursors. The best devices delivered power conversion efficiency (PCE) of 9.3 to 10.5%, thus coming close to the reference MAPbI3-based devices (PCE ≈ 12%). These results emphasize that all inorganic lead halide perovskites can successfully compete in terms of photovoltaic performance with the most widely used hybrid materials such as MAPbI3.

Design of indigo derivatives as environment-friendly organic semiconductors for sustainable organic electronics

We report the synthesis and systematic investigation of nine different indigo derivatives as promising materials for sustainable organic electronics. It has been shown that chemical design allows one to tune optoelectronic properties of indigoids as well as their semiconductor performance in OFETs. Fundamental correlations between the molecular structures of indigo derivatives, structural characteristics of their films, charge carrier transport properties and transistor characteristics have been revealed. Particularly important was lowering the LUMO energy levels of indigoids bearing strong electron withdrawing groups which improved dramatically ambient stability of n-type OFETs. Chemical structures of novel indigoids enabling truly air-stable n-channel OFET operation were proposed.

Exploring the Photovoltaic Performance of All-Inorganic Ag2PbI4/PbI2 Blends

We present an all-inorganic photoactive material composed of Ag2PbI4 and PbI2, which shows unexpectedly good photovoltaic performance in planar junction solar cells delivering external quantum efficiencies of ∼60% and light power conversion efficiencies of ∼3.9%. The revealed characteristics are among the best reported to date for metal halides with nonperovskite crystal structure. Most importantly, the obtained results suggest a possibility of reaching high photovoltaic efficiencies for binary and, probably, also ternary blends of different inorganic semiconductor materials. This approach, resembling the bulk heterojunction concept guiding the development of organic photovoltaics for two decades, opens wide opportunities for rational design of novel inorganic and hybrid materials for efficient and sustainable photovoltaic technologies.

Liquid crystalline side-chain triblock copolymers consisting of a nematic central subblock edged by photochromic azobenzene-containing fragments: their synthesis, structure and photooptical behaviour

For the first time, symmetrical photosensitive fully liquid crystalline side chain triblock copolymers (pAzo-b-pPhM-b-pAzo) and random copolymers (pAzo-ran-pPhM) with nematogenic phenyl benzoate (PhM) and photosensitive smectogenic azobenzene containing groups (Azo) were synthesized by the combination of RAFT polymerization and subsequent chemical modification. The central block of synthesized photochromic block copolymers contains 80 PhM groups, while the length of “peripheral” blocks includes 4 or 10 Azo units. The microphase separation structure is observed in the block copolymer when the length of a subblock with Azo groups reaches ten monomeric units. The influence of photochromic polymers’ molecular architecture (homopolymer, block copolymer and random copolymer) on the photochemical and photoorientation processes induced by light in their amorphous films has been revealed. The optical anisotropy induced in block copolymer films by illumination with linearly polarized 546 nm light was studied and the results were compared with those of the Azo homopolymer and of a random copolymer with a similar composition. It was found that practically only Azo groups are included in the process of photoinduced orientation in films of block copolymers, whereas the orientational cooperative effect of both azobenzene chromophore and phenyl benzoate mesogenic groups is observed in the case of a random copolymer.

Nanocomposites and high-modulus fibers based on ultrahigh-molecular-weight polyethylene and silicates: Synthesis, structure, and properties

Nanocomposites based on ultrahigh-molecular-weight polyethylene and inorganic fillers—such as organomodified layered aluminosilicates, aerosil, and diatomite—are prepared via polymerization filling. The polymerization of ethylene was conducted in the suspension mode with the use of a conventional Ziegler-Natta catalyst, TiCl4 + Al(i-Bu)3, under mild conditions (a temperature of 30°C and a pressure of 0.1MPa). The structure and properties of the composites are studied via X-ray diffraction analysis and DSC. The polyethylene matrix features a high enthalpy, a high melting temperature (up to 143°C), a crystallinity of 70–80%, a content of the monoclinic phase of 12–15%, and a bulk density of 0.05–0.15 g/cm3; the molecular mass is (1.5–1.6) × 106. High-modulus, high-strength fibers with an elastic modulus of 25–28 GPa and a strength of 0.65–0.70 GPa are prepared via direct solvent-free molding of nascent reactor powders based on ultrahigh-molecular-weight polyethylene filled (7 wt %) with aerosol or montmorillonite modified with vinyltrimethoxysilane.

Synthesis and properties of polyvinylpyrrolidone films containing iron nitrosyl complexes as nitric oxide (NO) donors with antitumor and antiseptic activities

New homogeneous water-soluble polyvinylpyrrolidone composites containing iron sulfur nitrosyl complexes as nitric oxide donors with antitumor and antiseptic activities were synthesized. The morphology of the composites in the solid state was examined by X-ray diffraction and scanning electron microscopy. The study by small-angle X-ray scattering showed that samples of the composites do not contain 10–100-nm aggregates and that iron sulfur nitrosyl complexes are uniformly distributed in polymer matrices. The percentage of NO-releasing iron sulfur nitrosyl complexes in the composites was determined by ESR spectroscopy. An amperometric analysis demonstrated that the polymer composites decompose to yield NO within a few seconds after the dissolution in water without additional thermal and photoactivation. The dependences of the amount of NO and the maximum level of NO release on the duration of the storage of aqueous solutions for all of the synthesized films were determined at pH 7.0. Some of the synthesized polymer composites retain NO-donor activity of the starting pharmacologically active iron nitrosyl complexes and can be recommended to be used as targeted delivery systems of this class of compounds to biological targets.

Investigation into the Morphology of Aliphatic Segmented Block Copolymers with Controlled Thickness of Crystals

In the present paper, aliphatic thermoelastoplastics, consisting of alternating segments of polytetrahydrofuran and monodisperse segments of glycine and β-alanine bisoxalamides, are studied. Phase transitions and the orientation of crystals are determined by experiments using X-ray structural analysis during the drawing process in situ. Two types of morphology have been revealed. Fibrillar crystals with chains oriented perpendicularly to the drawing direction are formed at low draw ratio values. At high deformation degrees, a fracture of large crystals and a reorientation of polymer chains along the drawing direction are observed. It is shown that the thickness of the hard block crystals is constant and independent of the sample thermal prehistory. The tilting angle of bisoxalamide chains is determined using four-spot small-angle patterns. It turns out that in the case of glycine the tilting angle is rather small (∼5–15°), while for alanine it reaches 24°. The flexible block crystallization during the drawing process at room temperature was found regardless of the block length. The surface free energy of hard block crystals proved to be rather low (∼18 erg/cm2), which is probably due to the entropic contribution from flexible blocks.