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Controlling the microstructure of hybrid halide perovskite thin films is essential for optimizing their performance in optoelectronic devices. It is well established that the strain state of the perovskite layer affects its stability. Likewise, the orientation of the perovskite lattice is a determining parameter as these materials have shown pronounced anisotropies in their physical and mechanical properties. In this work, the authors focus on the understanding of the mechanisms that govern the strain and texture observed in MAPbI3 thin films deposited on various oxide substrates. A thorough study of the evolution of the strain of the perovskite layer upon cooling down to room temperature from the crystallization temperature (100 °C) shows an essentially relaxed behavior of the perovskite layers. This result contradicts the commonly accepted hypothesis according to which MAPbI3 layers synthesized above ambient temperature are strained due to the large mismatch in the thermal expansion coefficients of the perovskite and its substrate. The texture in MAPbI3 layers is investigated by means of synchrotron full‐field diffraction X‐ray microscopy. This technique allows the direct observation of the [hh0] and [00l]‐oriented domains at the origin of the observed textures, demonstrating both their twin and ferroelastic nature. The stability of the different domain orientations is investigated by DFT calculations, illustrating the determining role of the chemical environment at the film‐substrate interface. PbI2‐ terminated surfaces are found to favor the [hh0] orientations while for MAI‐terminated ones, both [hh0] and [00l] domains are equally stabilized. The different results constitute an important step of clarification and understanding from the perspective of controlling the microstructure of perovskite layers. [ABSTRACT FROM AUTHOR]

An organogelator based on a N,N′-substituted H-bonding perylenebisimide (PBI-C10) self-assembles to form either a green J-type (form I) or a red H-type (form II) aggregate structure. The molecular packing of both polymorphs was determined from a combination of Transmission Electron Microscopy (TEM) (low dose electron diffraction and high resolution), Grazing incidence X-ray diffraction and polarized infrared spectroscopy. To that aim, highly oriented films have been prepared by mechanical rubbing at controlled film temperature and DFT calculations were performed to identify representative vibrational IR bands and their associated polarizations. H-Bonding between amides generates either a rectangular columnar phase (form I) in the dried gel or a hexagonal packing of supramolecular 21/1 helices with a long period of 97 Å (form II) in annealed thin films. In aligned films of form I, polarized FTIR spectroscopy helps determine the orientation of both intermolecular H-bonds and the PBI core with respect to the substrate. In form II, PBI-C10 molecules assemble into pairs to form off-centered 21/1 helices whose helical axis is made of strongly H-bonded amides. TEM investigations show that three 21/1 helices are packed in a frustrated trigonal structure formed by H-bonding. The Form I → Form II transformation implies a redistribution of a single population of strong intra-columnar H-bonds between amides in form I to a mixture of strong and weak H-bonds in the supramolecular helices, the strong H-bonds forming the spine of the helices. [ABSTRACT FROM AUTHOR]

In this review we present the results of our literature investigation into the electrical and thermal properties of carbon nanotube polymer composites. A short selection of data relating to conductive polymer composites with various fillers is provided for comparison. The effects of filler properties such as type and size, the use of hybrid fillers, fabrication methods for polymer composites and the importance of the modeling of the electronic and thermal transport mechanisms are discussed, as are more general factors influencing the properties of these composites. This review represents a comprehensive survey and constructive study and should serve as a useful reference tool for industrial and academic researchers working in this field. [ABSTRACT FROM AUTHOR]

This work is a reinvestigation of the impact of blend morphology and thermal annealing on the electrical performance of regioregular-P3HT:PC60BM bulk heterojunction organic solar cells. The morphological, structural, and electrical properties of the blend are experimentally investigated with atomic force microscopy, X-ray diffraction, and time-of-flight measurements. Current-voltage characteristics of photodiode devices are measured in the dark and under illumination. Finally, the existence of exponential electronic band tails due to gap states is experimentally confirmed by measuring the device spectral response in the subband gap regime. This method reveals the existence of a large density of gap states, which is partially and systematically reduced by thermal annealing. When the band tails are properly accounted for in the drift and diffusion simulations, experimentally measured charge transport characteristics, under both dark and illuminated conditions and as a function of annealing time, can be satisfactorily reproduced. This work further confirms the critical impact of tails states on the performance of solar cells. [ABSTRACT FROM AUTHOR]

Conjugated polymers form a remarkable class of macromolecules with fascinating electronic properties as well as structural features that make them very different from the more classical and flexible polyolefins. In thin films, the structure and the nanomorphology are two important parameters that control solid state properties such as charge transport. Due to the high anisotropy of electronic properties in conjugated polymers, it is essential to control both crystallization and domain orientation over large length scales. This review demonstrates that epitaxial growth is an original method for bringing macromolecules like regioregular poly(3-hexylthiophene) (P3HT) to a high level of order. Various orientation methods based on epitaxy are presented and the peculiar morphological and structural aspects of oriented P3HT, as analyzed by transmission electron microscopy (TEM), are described. The use of TEM on epitaxied layers is shown to shed some new light on the intriguing crystallization, structure, and growth of this key polymer for organic electronic applications. [ABSTRACT FROM AUTHOR]

Halide Perovskites Along with their impressive optoelectronic properties, a number of the elementary aspects of hybrid halide perovskites remain a mystery, as represented by the enigmatic Chesire cat looking down upon fascinated researchers. In article number 2103627 Stéphanie Pouget and co‐workers combine synchrotron experiments, laboratory X‐ray diffraction and calculations to address fundamental questions related to strain and texture in MAPbI3 thin films. [ABSTRACT FROM AUTHOR]

Halide perovskites, microstructure, strain, synchrotron, texture, thin layers, X-ray diffraction In article number 2103627 Stéphanie Pouget and co-workers combine synchrotron experiments, laboratory X-ray diffraction and calculations to address fundamental questions related to strain and texture in MAPbI SB 3 sb thin films. Keywords: halide perovskites; microstructure; strain; synchrotron; texture; thin layers; X-ray diffraction EN halide perovskites microstructure strain synchrotron texture thin layers X-ray diffraction 1 1 1 05/23/22 20220519 NES 220519 B Halide Perovskites b Along with their impressive optoelectronic properties, a number of the elementary aspects of hybrid halide perovskites remain a mystery, as represented by the enigmatic Chesire cat looking down upon fascinated researchers. [Extracted from the article]

Application of the master equation approach to the space-charge-limited transient situation is considered. The transient responses of thin organic films are simulated by solving the master equation of transport coupled with the Poisson equation. Hopping of the charge carriers between sites is described by the Miller–Abrahams formula. Sites with the Gaussian energetic distribution are localized on a Cartesian lattice. The solutions are calculated using the fully coupled Newton–Raphson method. The details of implementation permitting efficient stationary and transient simulation of unipolar transport are given. This approach gives much better agreement to the experimentally observed space-charge-limited current transient responses than the widely used drift-diffusion model. It is shown that the time position of the transient peak is affected by the contact barrier height. In the case of thin strongly disordered samples, the best observability of the peak is predicted for the intermediate values of the contact barrier. [ABSTRACT FROM PUBLISHER]

We have investigated the possibility of obtaining the conducting form of polyaniline (PANI) using a one-step preparation route. The polyaniline is chemically synthesized in presence of either 1,5-naphtalene disulfonic acid (NDSA) as a dopant or the couple 1,5-naphtalene disulfonic acid as a dopant and the chromotropic salt as a co-dopant (NDSA-Chromo). We present here the study of the spectroscopic, structural and electronic properties of the obtained salts of PANI. During this primary doping of PANI, only a single protonation by NDSA occurred. A co-protonation by HSO4−appeared impossible in the presence of an organic disulfonic acid of strong acidity. This conclusion was confirmed not only by the elemental analysis but also by FTIR. The spectroscopic studies (UV-Visible-NIR) showed localization of the charge carriers (polaron) in the synthesized PANI. Using this strategy, we hoped that each NDSA molecule might protonate two PANI amine sites to form a hierarchically ordered supramolecular structure. The obtained compounds show only a limited degree of crystallinity which is however sufficient to propose a possible structural organization. The adjunction of the co-dopant does not modify the local structure of the conducting material and conductivities in the 0.1 S/cm range are obtained for samples with partial doping level. Further improvements in processing can be achieved in particular by using different solvents for obtaining films. In this respect, further progress is possible and this preparation path is worth to be explored in the future. [ABSTRACT FROM PUBLISHER]

Two series of new soluble conjugated compounds containing tetrazine central ring have been synthesized. The three-ring compounds have been synthesized by the reaction of aryl cyanide (where aryl = thienyl, alkylthienyl, phenyl or pyridyl) with hydrazine followed by oxidation of the intermediate product with diethyl azodicarboxylate. The five-ring compounds have been prepared using two pathways: (i) reaction of 5-cyano-2,2′-bithiophene (or its alkyl derivative) with hydrazine; (ii) viaSuzuki or Stille coupling of 3,6-bis(5-bromo-2-thienyl)-1,2,4,5-tetrazine with a stannyl or boronate derivative of alkylthiophene. UV-vis spectroscopic properties of the synthesized compounds are strongly dependent on the nature of the aryl group, the position of the solubilizing substituent and the length of the molecule, showing the highest bathochromic shift (λmax> 440 nm) for five-ring compounds with alkyl groups attached to Cαcarbon in the terminal thienyl ring. An excellent linear correlation has been found for spectroscopically determined and theoretically calculated (TD-B3LYP/6-31G*) excitation energies. With the exception of dipyridyl derivative, the calculated lowest unoccupied molecular orbital (LUMO) level of the investigated molecules changes within a narrow range (from −2.63 to −2.41 eV), in line with the electrochemical data, which show a reversible reduction process with the redox potential varying from −1.23 V to −1.33 V (vs.Fc/Fc+). The electrochemically determined positions of the LUMO levels are consistently lower by 0.9 to 1.2 eV with respect to the calculated ones. All molecules readily crystallize. Single crystal studies of 3,6-bis(2,2′-bithien-5-yl)-1,2,4,5-tetrazine show that it crystallizes in a P21/cspace group whose structural arrangement is not very favorable to the charge carriers flow within the crystal. Powder diffraction studies of other derivatives have shown that their structural organization is sensitive to the position of the solubilizing substituent. In particular, the presence of alkyl groups attached to Cαcarbon in the terminal thienyl ring promotes the formation of a lamellar-type supramolecular organization. [ABSTRACT FROM AUTHOR]

The article discusses the highlights of various meetings on neutron scattering held in 2010. The 18th annual meeting of the French Neutron Scattering Society, held on June 4 discussed issues concerning neutrons and simulations. The "Bombannes" summer school focused on neutron scattering, X-ray and light sources. Meanwhile, the Jaca Summer School tackled neutron scattering techniques in nanoscience and biosciences.

This paper reports on hybrid, bioactive ceramic Ca-P-based coating formation on a Ti-6Al-7Nb alloy substrate to enhance the osseointegration process. The Ti alloy was anodized in a Ca3(PO4)2 suspension and then the additional layer was formed by the sol-gel technique to obtain a mixture of the calcium phosphate compounds. The oxide layer was porous and additional ceramic particles were formed after sol-gel treatment (scanning electron microscopy analysis coupled with energy-dispersive x-ray spectroscopy). The ceramic particles were formed on some parts of the oxide layer and did not completely fill the pores. The layer thickness of the anodized Ti alloy was comprised between 3.01 and 5.03 µm and increased to 7.52–12.30 µm after the formation of an additional layer. Post-treatment of the anodized Ti alloys caused a decrease in surface roughness, and the layer became strongly hydrophilic. Crystalline phase analysis (X-ray diffraction, XRD) showed that the hybrid layer was composed of TiO2 (anatase), Ca3(PO4)2, Ca10(PO4)6(OH)2 and a partially amorphous phase; thus, the layer was also analyzed by Raman spectroscopy. The hybrid layer showed worse adhesion to the substrate than the anodized layer only; however, the coating was not brittle, and the first delamination of the layer was determined at 1.84 ± 0.11 N during scratch-test measurement. The hybrid coating was favorable for collagen type I and lactoferrin adsorption, strongly influencing the proliferation of osteoblast-like MG-63 cells. The coatings were cytocompatible and may find applications in formation of the functional layers on long-term implants' surface after. [ABSTRACT FROM AUTHOR]

Hybrid poly(vinyl alcohol) and alginate membranes were investigated in the process of ethanol dehydration by pervaporation. As a filler, three types of particles containing iron element, i.e., hematite, magnetite, and iron(III) acetyloacetonate were used. The parameters describing transport properties and effectiveness of investigated membranes were evaluated. Additionally, the physico-chemical properties of the resulting membranes were studied. The influence of polymer matrix, choice of iron particles and their content in terms of effectiveness of membranes in the process of ethanol dehydration were considered. The results showed that hybrid alginate membranes were characterized by a better separation factor, while poly(vinyl alcohol) membranes by a better flux. The best parameters were obtained for membranes filled with 7 wt% of iron(III) acetyloacetonate. The separation factor and pervaporative separation index were equal to 19.69 and 15,998 g⋅m−2⋅h−1 for alginate membrane and 11.75 and 14,878 g⋅m−2⋅h−1 for poly(vinyl alcohol) membrane, respectively. [ABSTRACT FROM AUTHOR]

The chemical oxidation of alternating branched polyarylamines leads to the formation of radical cations, the presence of which was manifested by the appearance of new bands in the UV-visible-near infrared spectra. Spins of radical cations can be magnetically coupled. The nutation pulsed-EPR technique was used to determine the multiplicity of spin systems for different oxidant:polymer unit ratios. It was found that spins of polymers oxidized to a radical cation in each conjugated amine segment interact magnetically to form dominant quartet state (S = 3/2). Magnetization measurements confirmed the ferromagnetic interaction of spins, returning an exchange integral J = +0.75 meV. [ABSTRACT FROM AUTHOR]

Charge carrier mobilities and transport dispersivity are studied in hybrid films composed of poly(3-hexylthiophene) and CdSe nanocrystals by the time-of-flight method, using a field range of 105-106 V/cm. It is found that charge transport parameters pass through an optimum for 75 wt. % (36 vol. %) of nanocrystals in the polymer matrix, yielding balanced hole and electron mobilities around 10-3 cm2/V s. Changing the nanocrystal shape from spherical to branched increases the intersite coupling disorder in the hybrid whereas changing the surface ligands from stearate/oleylamine to pyridine decreases it. Both these modifications have an impact on the electric field dependence of the measured mobilities. [ABSTRACT FROM AUTHOR]