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Organic materials and blends have received a great deal of interests for application in large area, flexible, and low-cost organic/hybrid electronics. In this work the optical, structural and the electrical behaviors of a new active layer system composed by functionalized gold nanoparticles (AuNPs) and conjugated polymers, were investigated. For this purpose, gold nanoparticles with diameter of about 5 nm were chosen, coated with the bifunctional π-conjugated ligand (9,9-didodecyl-2,7-bis(acetylthio)fluorene, FL) for their high stability and easy dispersibility in organic solvents. The blends based on AuNPs and regioregular poly-3-hexylthiophene (P3HT) were prepared by adding an increasing percentage by weight of nanoparticles, i.e. from 10% to 90 wt%, in the P3HT polymeric matrix. The presence of nanoparticles was confirmed by UV-Vis spectroscopy, electron microscopy and X-ray diffraction techniques. The optical characterization of the composites demonstrated the possibility to tune the optical behavior of the P3HT by adding increasing percentages of AuNPs into the polymer matrix. Their inclusion results in a loss of P3HT crystallinity and in a simultaneous increase of the π-π interaction between the polythiophene chain and fluorene ligand. To better investigate the films, Grazing Incident X-ray Diffraction (GIXD) measurements were carried out and the blend containing 30 wt% of AuNPs in P3HT reveals an optimal condition, combining good structural order and interconnectivity in the polymer matrix. The electrical characterization of the AuNPs/P3HT blends reveals an improvement of the electrical conductivity in all the prepared blends, that show higher conductivity values compared to the pristine AuNPs and P3HT materials. The best performance is achieved adding 30 wt% of AuNPs to P3HT resulting in an enhancement of conductivity by about 350% compared to that of the pure polymer. This result could be of great interest for the realization of new conductive film composites to use in opto-electronic devices. [Display omitted] • Gold nanoparticles (AuNPs) and regioregular poly-3-hexylthiophene (P3HT) were blended in different weight percentages. • Tuning of the structural and optical features by increasing percentages of AuNPs into the P3HT matrix. • The electrical characterization of the AuNPs/P3HT blends reveals a substantial improvement of the conductivity. • The best performance is achieved adding 30%wt of AuNPs to P3HT with 350% enhancement of conductivity compared to pure P3HT. [ABSTRACT FROM AUTHOR]

Abstract: We show that both the morphology and crystal structure of regioregular poly(3-hexylthiophene) (RR-P3HT) films in organic field effect transistor (OFET) devices with top surface contacts are altered, when an electric field is applied. Grazing incidence X-ray diffraction (GIXD) analysis reveals a dramatic decrease in structural order in the non-linear current regime and, by contrast, much less pronounced structural changes of the (h 00) peaks in the linear current regime. Using for the first time resonance soft X-ray reflectivity (RSoXR) on RR-P3HT to avoid radiation damaged and to enhance the scope of the attained depth resolved information, we show that these changes are located in a several tens of nanometer thin sub-surface layer of the active polymer in the device. Furthermore, the RSoXR data reveal that the changes are strongly related to the C 1s→ π ∗ and C 1s→ σ ∗-resonances. In situ AFM measurements of the RR-P3HT device surface support the reciprocal space analysis results by showing a substantial softening and lateral expansion of the RR-P3HT films, when 20V are applied between the contacts. These morphological and structural changes are partially reversible in nature. [Copyright &y& Elsevier]

[Display omitted] Colloidal gold nanoparticles (AuNPs) functionalised with hydrophilic thiols can be used as drug delivery probes, thanks to their small size and hydrophilic character. AuNPs possess unique properties for their use in nanomedicine, especially in cancer treatment, as diagnostics and therapeutic tools. Thiol functionalised AuNPs were synthesised and loaded with methotrexate (MTX). Spectroscopic and morphostructural characterisations evidenced the stability of the colloids upon interaction with MTX. Solid state (GISAXS, GIWAXS, FESEM, TEM, FTIR-ATR, XPS) and dispersed phase (UV–Vis, DLS, ζ-potential, NMR, SAXS) experiments allowed to understand structure-properties correlations. The nanoconjugate was tested in vitro (MTT assays) against two neuroblastoma cell lines: SNJKP and IMR5 with overexpressed n -Myc. Molar drug encapsulation efficiency was optimised to be >70%. A non-covalent interaction between the π system and the carboxylate moiety belonging to MTX and the charged aminic group of one of the thiols was found. The MTX loading slightly decreased the structural order of the system and increased the distance between the AuNPs. Free AuNPs showed no cytotoxicity whereas the AuNPs-MTX nanoconjugate had a more potent effect when compared to free MTX. The active role of AuNPs was evidenced by permeation studies: an improvement on penetration of the drug inside cells was evidenced. [ABSTRACT FROM AUTHOR]

In this work, in situ studies of organic thin films under stretching are developed. A high efficiency PffBT4T-2OD π-conjugated polymer (PCE11) was coated directly on a stretchable substrate in order to examine the impact of tensile strain on the structural properties. For that purpose, in situ grazing incidence x-ray diffraction coupled with optical microscopic observations have been carried out to measure the structural parameters of PCE11 and to probe the mechanical behavior of polymer chains under uniaxial tensile load. It is observed that in the range between 0% and 15%–20% of stretching, the polymer chains become more oriented. Meanwhile, an increase in negative values of deformation, i.e., compression of the polymer chains along the film normal was measured. Beyond this range of stretching, the polymer order declined and the stress was relaxed. This relaxation is explained by the increased number of cracks spreading over the entire film as observed using optical microscopy. [ABSTRACT FROM AUTHOR]

Organic field-effect transistors (OFETs) were fabricated by depositing a regioregular poly(3-hexylthiophene) (P3HT) active layer using a dip-coating method. The field-effect mobility in OFETs depends on chain orientation and crystallinity and is related to direction and withdrawal speed with respect to the source/drain orientation. In this paper, how to control the structural and transport properties of P3HT films by coating parallel and perpendicular to the dipping direction is demonstrated. X-ray diffraction curves taken in the perpendicular direction exhibit a higher degree of crystalline ordering and edge-on conformation compared with those in the parallel direction; this finding correlates with the directional anisotropy of the OFET mobility. Both structural anisotropy and transport properties are enhanced upon thermal treatment. [ABSTRACT FROM AUTHOR]

Structural and electrical properties of semicrystalline P3HT cast films onto Si/SiO2 surface are studied during the solidification under applied electric field in lateral OFET geometry. During evaporation of the solvent, the formation of P3HT crystallites is monitored simultaneously by time-resolved X-ray diffraction and by source-drain current measurements. The electrical current is reaching its maximum in two pronounced regimes already before complete solidification of the polymer as detected by X-ray diffraction intensities. The monitored complex time dependence of current and X-ray intensities reveals a highest conducting level for the gel-like state. [ABSTRACT FROM AUTHOR]

The impact of thermal annealing on the growth of crystallinenanodomainsof poly(3-alkylthiophene) (P3AT) in thin films (15–20 nm thick)was investigated as a function of length of alkyl side chain by combinedlow-dose high-resolution transmission electron microscopy (HR-TEM)and grazing incidence X-ray diffraction (GIXD). Statistical analysisof the data yields the characteristic dimensions of the face-on orientedP3AT nanocrystals, i.e., average stem length lcalong backbones and lateral dimension perpendicular to thestems laalong side chains. The followingtrends were identified: (i) in as-spin-coated films, the proportionof face-on oriented nanocrystals increases with the number of carbonatoms in the side chain, (ii) annealing favors the lateral in-planegrowth of the nanocrystals along the side chain direction (aP3ATaxis), (iii) for a given P3AT, the proportion offace-on oriented domains increases with annealing temperature, (iv)lateral growth along the aP3ATaxis is mostefficient for the longer octyl side chains, and (v) thermal annealinginduces only modest lamellar thickening which is limited by the poorslide diffusion of π-stacked P3AT chains as opposed to lateralgrowth favored by weak van der Waals interactions between layers of n-alkyl side chains. The increase in the population of face-onoriented crystallites, observed when the length of the side chainincreases, coincides with a corresponding decrease in the field effectmobility in annealed P3AT thin films. [ABSTRACT FROM AUTHOR]

The synthesis of a series of novel A-π-D-π-A oligomers bearing either electron-donating dithieno[3,2- b :2′,3′- d ]silole (DTS) or dithieno[3,2- b :2′,3′- d ]pyrrole (DTP) units linked through a bithiophene π-bridge with the electron-withdrawing methyldicyanovinyl (DCV) or N-ethylrhodanine (Rh) groups is described. In order to evaluate the effects of different donor-acceptor combinations on various physical properties of the oligomers they are comprehensively studied by UV–Vis spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and cyclic voltammetry (CV). Replacing the DTS by DTP as well as the DCV by Rh leads to increasing of HOMO energy levels and slight decreasing of LUMO energy levels, respectively. The DTP-based oligomers have a red shift in absorption spectra and an increased solubility as compared to the DTS-based analogs. Replacing the acceptor DCV unit by Rh also results in significantly higher solubility, but the Rh-based oligomers exhibit weaker intermolecular interactions, poorer optical absorption of sun light as well as lower charge carrier mobility in blends. Altogether, the structural improvement of the DTS-DCV and DTP-DCV blends upon annealing correlates well with the observed photovoltaic performances in organic solar cells. These results give more insight how to fine-tune and predict physical properties and photovoltaic performance of small A-π-D-π-A molecules having different donor-acceptor combinations in their chemical structures and thus providing a molecular design guideline for the next generation of high-performance photovoltaic materials. [ABSTRACT FROM AUTHOR]

In the present work the role of the thermal treatment on the reorganization of gold nanoparticles (AuNPs) functionalized with a π-conjugated dithiol ligand, namely 9,9-didodecyl-2,7-bis-thiofluorene, is studied by grazing incidence X-ray diffraction technique. For a detailed investigation of the structural changes and reorganization occurring in the AuNPs network and of the monitoring of complex interactions between nanoparticles, the line profiles are analyzed in out-of-plane and in-plane directions. The obtained data support the idea of the formation of a uniform network of nanoparticles that after annealing are extended from hexagonal to cubic arrangement. [ABSTRACT FROM AUTHOR]

Length of the terminal alkyl chains at dicyanovinyl (DCV) groups of two dithienosilole (DTS) containing small molecules ( DTS(Oct)2-(2T-DCV-Me)2 and DTS(Oct)2-(2T-DCV-Hex)2) is investigated to evaluate how this affects the molecular solubility and blend morphology as well as their performance in bulk heterojunction organic solar cells (OSCs). While the DTS(Oct)2-(2T-DCVMe)2 (a solubility of 5 mg mL-1 ) system exhibits both high short circuit current density (Jsc) and high fill factor, the DTS(Oct)2-(2T-DCV-Hex)2 (a solubility of 24 mg mL-1) system in contrast suffers from a poor blend morphology as examined by atomic force morphology and grazing incidence X-ray scattering measurements, which limit the photovoltaic properties. The charge generation, transport, and recombination dynamics associated with the limited device performance are investigated for both systems. Nongeminate recombination losses in DTS(Oct)2-(2T-DCV-Hex)2 system are demonstrated to be significant by combining space charge limited current analysis and light intensity dependence of current-voltage characteristics in combination with photogenerated charge carrier extraction by linearly increasing voltage and transient photovoltage measurements. DTS(Oct)2 -(2T-DCV-Me)2 in contrast performs nearly ideal with no evidence of nongeminate recombination, space charge effects, or mobility limitation. These results demonstrate the importance of alkyl chain engineering for solution-processed OSCs based on small molecules as an essential design tool to overcome transport limitations. [ABSTRACT FROM AUTHOR]

Length of the terminal alkyl chains at dicyanovinyl (DCV) groups of two dithienosilole (DTS) containing small molecules ( DTS(Oct)2-(2T-DCV-Me)2 and DTS(Oct)2-(2T-DCV-Hex)2 ) is investigated to evaluate how this affects the molecular solubility and blend morphology as well as their performance in bulk heterojunction organic solar cells (OSCs). While the DTS(Oct)2-(2T-DCV-Me)2 (a solubility of 5 mg mL−1) system exhibits both high short circuit current density ( Jsc) and high fill factor, the DTS(Oct)2-(2T-DCV-Hex)2 (a solubility of 24 mg mL−1) system in contrast suffers from a poor blend morphology as examined by atomic force morphology and grazing incidence X-ray scattering measurements, which limit the photovoltaic properties. The charge generation, transport, and recombination dynamics associated with the limited device performance are investigated for both systems. Nongeminate recombination losses in DTS(Oct)2-(2T-DCV-Hex)2 system are demonstrated to be significant by combining space charge limited current analysis and light intensity dependence of current-voltage characteristics in combination with photogenerated charge carrier extraction by linearly increasing voltage and transient photovoltage measurements. DTS(Oct)2-(2T-DCV-Me)2 in contrast performs nearly ideal with no evidence of nongeminate recombination, space charge effects, or mobility limitation. These results demonstrate the importance of alkyl chain engineering for solution-processed OSCs based on small molecules as an essential design tool to overcome transport limitations. [ABSTRACT FROM AUTHOR]

X-ray and electron diffraction analyses were carried out under various geometries to investigate the role of alkyl side chain length on the structural properties of regioregular poly(3-alkylthiophene) (RR-P3AT) thin films by sequentially increasing the alkyl side chain length from n-pentyl till n-octyl. P3AT thin films with different thicknesses were drop cast at room temperature (RT) and low temperature (−30 °C) for the structural analysis. A thorough X-ray diffraction, transmission electron microscopic, field effect transistor and photoluminescence (PL) investigations revealed the following: (i) texturing of RT cast P3AT thin films along the out-of-plane direction on decreasing the alkyl side chain length, (ii) poor π–π stacking of P3AT crystallites on increasing the alkyl side chain length, which results from the increased steric hindrance between the grafted alkyl side chains, (iii) such poor π–π stacking of P3ATs on increasing the alkyl side chain length eventually found to hinder the mobility of charge carriers, and (iv) evolution of well defined vibronic side bands in the PL spectra of −30 °C cast films confirm the formation of highly crystalline films as compared to the RT cast ones. Highly edge-on oriented and uniform thin films can be fabricated by optimizing the cast temperature and concentration of the solution. [ABSTRACT FROM AUTHOR]

The impact of alkyl side-chain substituents on conjugated polymers on the photovoltaic properties of bulk heterojunction (BHJ) solar cells has been studied extensively, but their impact on small molecules has not received adequate attention. To reveal the effect of side chains, a series of star-shaped molecules based on a triphenylamine (TPA) core, bithiophene, and dicyanovinyl units derivatized with various alkyl end-capping groups of methyl, ethyl, hexyl and dodecyl is synthesiyed and studied to comprehensively investigate structure-properties relationships. UV-vis absorption and cyclic voltammetry data show that variations of alkyl chain length have little influence on the absorption and highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) levels. However, these seemingly negligible changes have a pronounced impact on the morphology of BHJ thin films as well as their charge carrier separation and transportation, which in turn influences the photovoltaic properties of these small-molecule-based BHJ devices. Solution-processed organic solar cells (OSCs) based on the small molecule with the shortest methyl end groups exhibit high short circuit current ( Jsc) and fill factor (FF), with an efficiency as high as 4.76% without any post-treatments; these are among the highest reported for solution-processed OSCs based on star-shaped molecules. [ABSTRACT FROM AUTHOR]

Different techniques for a relatively fast self-assembledmonolayerfilm formation such as Langmuir–Blodgett (LB), spin-coating,and dip-coating methods have been compared using chloro[11-(5′′′′-ethyl-2,2′:5′,2″:5‴,2‴:5‴,2′′′′-quinquethiophene-5-yl)undecyl]dimethylsilaneas a reactive precursor. It was shown that both spin-coating and LBtechniques are very promising methods for preparation of highly orderedmonolayer films of organosilicon-functionalized quinquethiophene withvertical orientation of oligothiophene fragments, while dip-coatinggives only partial coverage. Optimal conditions for complete fillingout the substrate surface by the quinquethiophene-containing monolayerby spin-coating and LB methods have been found. Grazing incidenceX-ray diffraction measurements confirmed formation of in-plane crystallineorder within the monolayer film. Changes in the layer structure wereestablished by X-ray reflectivity and grazing incidence X-ray diffractionmethods. [ABSTRACT FROM AUTHOR]

Calcium titanate-CaTiO3 (perovskite) has been used in various industrial applications due to its dopant/doping mechanisms. Manipulation of defective grain boundaries in the structure of perovskite is essential to maximize mechanical properties and stability; therefore, the structure of perovskite has attracted attention, because without fully understanding the perovskite structure and diffracted planes, dopant/doping mechanisms cannot be understood. In this study, the areas and locations of atoms and diffracted planes were designed and investigated. In this research, the relationship between Young's modulus and planar density of unit cell, super cells (2 × 2 × 2) and symmetry cells of nano CaTiO3 is investigated. Elastic constant, elastic compliance and Young's modulus value were recorded with the ultrasonic pulse-echo technique. The results were C11 = 330.89 GPa, C12 = 93.03 GPa, C44 = 94.91 GPa and E = 153.87 GPa respectively. Young's modulus values of CaTiO3 extracted by planar density were calculated 162.62 GPa, 151.71 GPa and 152.21 GPa for unit cell, super cells (2 × 2 × 2) and symmetry cells, respectively. Young's modulus value extracted by planar density of symmetry cells was in good agreement with Young's modulus value measured via ultrasonic pulse-echo. [ABSTRACT FROM AUTHOR]

We describe the impact of tensile strains on the structural properties of thin films composed of PffBT4T-2OD π-conjugated polymer and PC71BM fullerenes coated on a stretchable substrate, based on a novel approach using in situ studies of flexible organic thin films. In situ grazing incidence X-ray diffraction (GIXD) measurements were carried out to probe the ordering of polymers and to measure the strain of the polymer chains under uniaxial tensile tests. A maximum 10% tensile stretching was applied (i.e., beyond the relaxation threshold). Interestingly we found different behaviors upon stretching the polymer: fullerene blends with the modified polymer; fullerene blends with the 1,8-Diiodooctane (DIO) additive. Overall, the strain in the system was almost twice as low in the presence of additive. The inclusion of additive was found to help in stabilizing the system and, in particular, the π–π packing of the donor polymer chains. [ABSTRACT FROM AUTHOR]

The fundamental nature of charge transport in highly ordered organic semiconductors is under constant debate. At cryogenic temperatures, effects within the semiconductor such as traps or the interaction of charge carriers with the insulating substrate (dipolar disorder or Fröhlich polarons) are known to limit carrier motion. In comparison, at elevated temperatures, where charge carrier mobility often also decreases as function of temperature, phonon scattering or dynamic disorder are frequently discussed mechanisms, but the exact microscopic cause that limits carrier motion is debated. Here, the mobility in the temperature range between 200 and 420 K as function of carrier density is explored in highly ordered perylene‐diimide from 3 to 9 nm thin films. It is observed that above room temperature increasing the gate electric field or decreasing the semiconducting film thickness leads to a suppression of the charge carrier mobility. Via X‐ray diffraction measurements at various temperatures and electric fields, changes of the thin film structure are excluded as cause for the observed mobility decrease. The experimental findings point toward scattering sites or traps at the semiconductor–dielectric interface, or in the dielectric as limiting factor for carrier mobility, whose role is usually neglected at elevated temperatures. A systematic study of charge transport in solution‐deposited, monolayer‐thin organic semiconductors with an electron mobility above 1 cm² V−1 s−1 is combined with conductive atomic‐force microscopy measurements to uncover the detrimental role of the dielectric–semiconductor interface on carrier mobility. This explains the surprising finding of decreasing mobility with increasing charge carrier density at elevated temperatures. [ABSTRACT FROM AUTHOR]