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The present work proposes a method and an apparatus that allows the in vitro diagnostic analysis of biological samples to be carried out by analyzing the light radiation transmitted through the sample. An OLED (Organic LED) source, with broad emission spectrum for white light, was used; the optical path of the light radiation emitted by the source has been adapted to the specific wavelengths of the system (405 nm, 450 nm, 492 nm, 550 nm, 620 nm) and the detection of the signal was carried out through the use of an OPD (organic photodiode) with the appropriate photoresponse. To suitably select the analysis signal, a series of photonic crystals have been used, with the aim to also obtain a bandwidth of less than 10 nm as required by the solutions already present on the market. The proposed system gives the opportunity to reduce the overall dimensions of the analyzer compared to the systems existing on the market, avoiding the use of supplementary optical fibers and interference filters.

Background and aims: Acquired Neuromyotonia (NMT) is an autoimmune condition frequently associated with anti-contactin-associated-protein-like-2 (Caspr2) antibodies. NMT can occur as a paraneoplastic disorder in patients with thymoma, alone or in combination with Myasthenia Gravis (MG). Recently, antibodies against netrin-1-receptors (DCC and UNC5A) have been reported as predictors of thymoma in 6/9 patients with concomitant NMT and MG. We aimed to clinically characterize a large cohort of patients with thymoma-associated MG, and to explore serological correlation of NMT symptoms. Methods: 268 consecutive patients with thymoma-associated MG were retrospectively collected. NMT was defined as muscle twitching/cramps in at least 2 skeletal districts. Patients with NMT(23) were screened for anti-neuronal antibodies by immunohistochemistry on rat brain and cell based assay. Results: 23/268 patients developed NMT symptoms (muscle twitching, 3; cramps, 3, or both, 17). Overall, 33/268 patients with thymoma had a tumor recurrence, which was more frequent in those with (8/23) vs those without NMT (25/245, p=0.003). NMT onset preceded the tumor recurrence in 5/6 patients. In univariate analysis predictors of thymoma recurrence were younger age at thymectomy (odds ratio-OR:0.95, confidence interval-CI:0.93-0.97), Masaoka staging (OR:10.73, CI:2.38-48.36) and NMT (OR:4.69, CI:1.76-12.46). 6 patients with NMT had anti-neuronal antibodies (patient#1: Caspr2; patient#2: AMPAR; patient#3: DCC; patient#4: LGI1; patient#5: Caspr2+LGI1+DCC+UNC5A; patient#6: Caspr2+LGI1+DCC). Thymoma recurrence was found less frequently in negative (3/17) vs positive patients with NMT (4/6, #1, #2, #5 and #6; p=0.045). Conclusion: The occurrence of NMT symptoms in patients with thymoma-associated MG can predict tumor recurrence, and warrants a closer oncologic follow-up. Anti-neuronal surface autoantibodies may be useful to further stratify the recurrence risk. Disclosure: This work was funded by the ‘Ricerca finalizzata ministeriale 2015-2017’ provided by the Italian ministry of health

In this work, we compared the photovoltaic performance of standard and inverted polymer solar cells with the aim to elucidate the origin of the different current output. We realized devices with both architectures using a blend film of poly[(4,8-bis-(2-ethylhexyloxy)-benzo[1,2-b:4,5-b′]dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiopene)-2,6-diyl] /[6,6]-phenyl C71 butyric acid methyl ester (PBDTTT-C:[70]PCBM). The standard cell sequence is ITO/PEDOT:PSS/PBDTTT-C:[70]PCBM/Ca/Al and the inverted one is ITO/ZnO/PBDTTT-C:[70]PCBM/MoO3/Ag. The inverted architecture shows better performances compared to the standard one mainly in terms of current output. The optical modeling has revealed that this architecture allows more photons to be absorbed in the blend film, giving rise to an higher current output, although the observed improvement cannot be completely attributed to the calculated higher absorption of the incoming light. By using the impedance spectroscopy analysis, we found that the inverted device architecture has higher values for the interface trap time constant and the density of interface states. Both parameters contribute to retain the charge collection efficient, compared to the standard configuration, despite the increased charge carrier density and to further improve the current output. © 2016 Elsevier B.V. All rights reserved.

Substoichiometric molybdenum oxide (MoOx) has good potential as a hole-collecting layer in solar cells. In this paper, we report on the application of ultrathin evaporated MoOx as a hole collector at the back side of two distinct photovoltaic technologies: polymeric and silicon heterojunction (SHJ). In the case of polymer solar cells, we test MoOx as a hole transport layer in devices with inverted architecture. The higher transparency of the MoOx film, compared to the commonly used poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), allows an enhanced back reflected light into the photoactive layer, thus boosting the photogeneration, as found from the illuminated J-V and external quantum efficiency (EQE) curves. The higher fill factor (FF) of the MoOx-based device also suggests an improved charge collection efficiency compared to the cells with PEDOT:PSS. As for SHJ solar cells, we show that MoOx offers the means for dopant-free hole collection with both p-type and n-type Si wafers. In the present comparison over planar test structures with Ag back reflecting electrodes, we observe an efficiency gain of approximately 1% absolute against a baseline with a conventional p-type amorphous silicon hole collector. The gain is linked to the increased VOC, which is likely due to the reduced recombination at the Si wafer.

Many research efforts are focused toward significant improvements of polymeric solar cells efficiency, energy harvesting range, time, and environmental stability. Particular attention is given to hybrid organic/inorganic composites constituted of polymer/lead chalcogenides (PbS and PbSe) nanocrystals (NCs) to extend the spectral sensitivity of cells to near-infrared wavelengths. In this work we report the synthesis and characterization of PbS nanocrystals with absorption edge at 984 nm. The nanocrystals have a cubic crystal structure and size of about 2 nm as found by X-ray diffraction analysis. They were combined with poly(3-hexylthiophene) (P3HT) polymer to obtain P3HT:PbS blends with different PbS loadings. A post-deposition ligand exchange on PbS NCs by 1,2-ethanedithiol (EDT) allowed a better interaction between polymer and nanocrystals as showed by fluorescence measurements. The P3HT:PbS blends were deposited and treated by a layer by layer spin coating process and used as active layer in solar cells having structure glass/ITO/PEDOT:PSS/blend/Al. The major result obtained for this hybrid system is an increase of PCE by about two orders of magnitude with respect to analogous reported cells where a post-deposition ligand exchange was performed.

In this work we improved the performance of ITO-free polymer solar cells (PSCs) by incorporating silver nanoparticles (AgNPs) in the highly conductive (HC) PEDOT:PSS anode. The AgNPs were synthetized in-situ in the PEDOT:PSS water dispersion. This anode was used to realize PSCs with the following geometry: glass/HC-PEDOT:PSS/PEDOT:PSS/PBDTTT-C:[70]PCBM/Ca/Al. All the devices were characterized by UV-VIS spectroscopy, impedance spectroscopy, IV light, IV dark and quantum efficiency measurements. The presence of AgNPs in the HC-PEDOT:PSS anode contributes to improve the absorption of the photoactive layer and to lower the resistivity of the anode.

Half titanocenes (CpCH2CH2O)TiCl21 and (CpCH2CH2 OCH3)TiCl32, activated by methylaluminoxane are tested in styrene–1,3-butadiene copolymerization. The titanocene 1 is able to copolymerize styrene and 1,3-butadiene, with a facile procedure, to give products with high molecular weight. The analysis of microstructure by 13C-NMR reveals that the styrene homosequences in copolymers are in syndiotactic arrangement, while the butadiene homosequences are, prevailingly, in 1,4-cis configuration, according with behavior of 1 in the homopolymerizations of styrene and 1,3-butadiene, respectively. The reactivity ratios of copolymerization are estimated by diad composition analysis. All obtained copolymers have r1 × r2 values much larger than 1, indicating blocky nature of homosequences. The structural characterization by wide-angle X-ray powder diffraction and differential scanning calorimetry indicates that all copolymers are crystalline, with Tm varying from 171 to 239 °C, depending on the styrene content. The titanocene 2 did not succeed in styrene–1,3-butadiene copolymerization, giving rise to a blend of homopolymers. Compounds 1 and 2 were also tested in the polymerization of several conjugated dienes, and the obtained results were very useful to rationalize the behavior of both catalysts in the copolymerization of styrene and butadiene. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 815–822, 2010

Random styrene-ethylene copolymers have been synthesized by the hydrogenation of styrene-butadiene copolymers. The samples were characterized by 13 C NMR spectroscopy, X-ray powder diffraction, thermal analysis, and Fourier transform IR (FTIR) spectroscopy. In the 13 C NMR spectra, the resonance of the methylene carbon next to a methine bearing a phenyl group presents splitting due to its diastereotopic positions with respect to the phenyl substituents of the second and third inserted styrene units. A definitive assignment of the resonances of the SEES sequences (S = styrene, E = ethylene) was obtained by synthesis of a suitable model compound: 5,10-diphenyl-pentadecane. X-ray powder diffraction and thermal analysis show that these samples are amorphous. This is probably due to the shortness of the ethylene and styrene sequences in the copolymers. DSC thermograms show a single glass transition, at a intermediate temperature, between the Tg values of polystyrene and polyethylene, depending on the styrene content in the chain. FTIR spectra indicate the presence of styrene sequences in an isotactic arrangement.

The performances and the stability of a polymer solar cell (PSC) mainly depend on the architecture of the device and the materials used for the fabrication (photoactive and interface layers and contacts). In this work we made a comparative study between standard and inverted PSCs having an identical pair of hole and electron transport layers: molybdenum trioxide (MoO3) and poly[(9,9-bis(3'-(N,Ndimethylamino) propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN), respectively. We realized devices using a blend film of poly[(4,8-bis-(2-ethylhexyloxy)-benzo[1,2-b;4,5-b']dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiopene)-2,6-diyl]/[6,6]-phenyl C71 butyric acid methyl ester (PBDTTT-C:[70]PCBM). The standard and inverted cells sequences were ITO/MoO3/PBDTTT-C:[70]PCBM/PFN/Ag and ITO/PFN/PBDTTT-C:[70]PCBM/MoO3/Ag, respectively. We studied the performances of both kinds of devices in order to investigate the influence of the architecture (standard vs inverted) on the performance of the solar cells. All the devices were characterized by IV light, IV dark and quantum efficiency measurements. The best device reached a power conversion efficiency of 6%. The inverted device has an improved current output compared to the standard one. In order to elucidate the absorption of photons inside the blend, we performed the optical modeling of the devices using the transfer matrix formalism and we simulated the effective absorption in the photoactive layer and the optical electric field inside the devices.

Transparent metal oxides became an important class of low-temperature solution-processed electron transport layers (ETLs) for inverted polymer solar cells (PSCs) due to their high optical transparency in the visible range, relatively good electrical conductivity and tunable work function. In this work we made a comparative study between the electrical performances of devices realized with various metal oxides as ETLs: ZnO, ZnO:Al and TiOx. These oxides were prepared by low-temperature solution process techniques and used in PSCs with the configuration glass/Indium tin oxide (ITO)/ETL/photoactive layer/MoO3/Ag. The photoactive layer was a blend of poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] and [6,6]-phenyl C71 butyric acid methyl ester. The best power conversion efficiency (9.1%) under simulated AM1.5G illumination of 100 mW/cm2, was achieved for the PSC fabricated using a ZnO:Al interlayer. In order to elucidate the electrical processes at the interfaces between the ETL and the blend, impedance spectroscopy analysis was carried out. The ZnO:Al PSC shows better charge transfer properties between the active layer and the ITO and longer charge carrier lifetime. These factors contribute to improve the fill factor and increase the current output leading to an higher power conversion efficiency.

The relationships between the structure and the viscoelastic properties of freeze/thaw PVA hydrogels obtained by repeatedly freezing and thawing dilute solutions of PVA in D 2 O(11% w/w PVA) in as-prepared and rehydrated states are investigated. Our results indicate that the PVA chains and solvent molecules are organized at different hierarchical length scales, which include the presence of micro-and macro-pores, into a network scaffolding. The porous network is ensured by the presence of crystallites, which act as knots interconnected by portions of PVA chains swollen by the solvent. X-ray diffraction and SANS techniques are used to obtain structural information at short (angstroms) and medium (nanometers) ranges of length scales, concerning the crystallinity, the size of small crystalline aggregates and the average distance between crystallites in PVA hydrogels. Indirect information concerning the structural organization on the large length scales (microns) are provided by viscoelastic measurements. The dynamic shear elastic moduli at low frequency and low strain amplitude, G', are determined and related to the degree of crystallinity. These data indicate that a minimum crystallinity of 1% is required for these PVA samples to exhibit gel behaviour and have allowed obtaining the order of magnitude of the average mesh size in these gels. Finally, it is shown that the negative effect of aging, inducing worse physical and mechanical properties in these systems, may be prevented using a drying/re-hydration protocol able to keep the physical properties of the as-prepared PVA hydrogels.

The structural organization of matter in poly(vinyl alcohol) (PVA) hydrogels obtained by repeatedly freezing and thawing dilute solutions of PVA in D2O is investigated by use of small-angle neutron scattering measurements (SANS). This study is the first systematic and quantitative investigation in the medium range of length scales on PVA hydrogels obtained by freezing and thawing techniques. The studied gels have a complex hierarchical structure, extending over a wide range of length scales. The structural organization on the micron length scale originates from the presence of two separated phases constituted by polymer-rich and polymer-poor regions. The network structure may be interpreted in terms of the connectivity of the regions occupied by the polymer-rich phase, which extend over the macroscopic dimensions of the sample. The organization on the medium length scale is provided by the presence of small crystallites, fringed micelle-like, within the polymer-rich phase. In these regions, the crystals are highly connected by swollen amorphous tie chains. The presence of these tie chains ensures the connectivity of the macroscopic network. The structural organization on the short length scale is essentially provided by the relative arrangement of chains within the crystallites and in the swollen amorphous zones. The PVA hydrogel structure has been modeled as a collection of polydisperse and homogeneous spherical crystallites, interacting via hard-spheres potential. SANS experiments permitted us to obtain values of the crystallite size of about 33 Angstrom, of the volume fraction of polymer-rich phase of the order of 1% and a value of the average crystallite-crystallite correlation distances of the order of a few tens of nanometers, independent of the imposed number of freeze/thaw cycles (n), for n > 1. The present analysis also indicates that the structure of the gel obtained imposing a single freeze/thaw cycle is somehow intermediate between the structure of the homogeneous starting solution and the structure of the already well-formed sample obtained by imposing two consecutive cycles.

The structure of physical poly(vinyl alcohol) (PVA) hydrogels prepared by subjecting a PVA/D2O solution (11% w/w PVA) to freeze (−22 °C)/thaw (+25 °C) cycles has been systematically investigated by X-ray powder diffraction technique as a function of the number of cycles and aging time. The structural analysis has been extended to PVA “dried gels” and PVA hydrogels obtained by rehydrating the dried samples. The results of the present analysis confirm that highly stable PVA hydrogels, with a water uptake higher than 80%, may be obtained upon freeze/thaw cycles. The X-ray diffraction profiles of PVA hydrogels have been interpreted in terms of three components: “free water”, crystalline PVA aggregates, and swollen amorphous PVA. The degree of crystallinity and the size of the crystals increase with increasing the number of freeze/thaw cycles and the aging time. Our results support the hypothesis that PVA hydrogels have a porous structure, with pores mainly occupied by water. The porous walls consist of swoll...

The structure and rheological behavior of atactic poly(vinyl alcohol) (a-PVA) hydrogels prepared by freeze/thaw cycles were investigated as a function of polymer concentration and number of freeze/thaw cycles. The presence of phases with different mobilities was observed using 13 C CP/MAS and DP/MAS NMR experiments. The degree of crystallinity of the a-PVA-rich phase was determined by 1 H NMR free decay experiments. Measurements of the shear storage and loss modulus were performed at a fixed frequency of 1 Hz and a strain value of 0.1%, i.e. under conditions where the deformation imposed on the gel structure is entirely reversible. Results thus obtained showed that an increase in the number of freeze/thaw cycles induces an increase in the degree of crystallinity in the polymer-rich phase together with an increase in the storage modulus. The a-PVA hydrogels became more fragile as the number of freeze/thaw cycles was increased. Moreover, both the percentage of protons in a rigid environment measured by 1 H NMR and the storage modulus values tended to a limiting value after six freeze/thaw cycles. These results show that the first five or six freeze/thaw cycles play a very important role in determining the hydrogel structure and rheological properties. A more detailed comparison of NMR and rheological data led to the conclusion that the storage modulus is mainly controlled by the a-PVA crystallinity while the hydrogen bond interactions have a much smaller contribution.

In this work, highly conductive and transparent films based on poly(3,4 ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) doped with dimethyl sulfoxide (DMSO) were printed onto a flexible substrate, the polyethylene naphthalate (PEN), using the gravure printing method. Gravure-printed DMSO-PEDOT:PSS ink suitably modified with isopropanol was developed and used as anode in flexible solar cells replacing the commonly used anode, that is, Indium Tin Oxide (ITO). Several inks were prepared and characterized in terms of viscosity and surface energy and tested by gravure printing. The wettability of the PEN substrate was investigated through contact angle measurements. For comparison, the anodic conductive polymer was also spin coated on the PEN substrate using an ink suitable for this technique. The films produced with both the techniques, gravure printing and spin coating, each using a proper ink, were characterized in terms of structure and physical–chemical properties. The printed layers were employed as anodes into ITO free-polymer solar cells based on a bulk heterojunction of Poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno [3,4-b]thiophenediyl}) (PTB7) and [6,6]-phenyl C70-butyric acid methyl ester ([70]PCBM). The performances of the devices with printed and spin coated polymeric anode were compared. The cell with the spin-coated anode reached a power conversion efficiency of 3% while the corresponding device with the printed anode a value around 2%. POLYM. COMPOS., 36:1104–1109, 2015. © 2015 Society of Plastics Engineers

In this work, we report the application of a sol–gel derived ZnO thin film as a buffer layer for high efficiency inverted polymer solar cells. ZnO films are widely used in such devices because they have a relatively high electron mobility, high transparency and environmental stability. The ZnO precursor was prepared by dissolving zinc acetate and ethanolamine in the 2-methoxyethanol. ZnO thin films were then deposited on indium tin oxide (ITO)/glass substrates by spin coating the above solution. Inverted polymer solar cells with the configuration ITO/ZnO/photoactive layer/MoOx/Ag were realized in order to investigate the performance of ZnO thin film. The photoactive layer is a blend of poly[(4,8-bis-(2-ethylhexyloxy)-benzo[1,2-b;4,5-b′]dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiophene)-2,6-diyl] (PBDTTT-C) and [6,6]-phenyl C71 butyric acid methyl ester ([70]PCBM) (1:1.5 w/w). We made a comparative study of the photovoltaic behavior of devices with ZnO films deposited using different sol–gel recipes. In particular, we varied the zinc acetate/ethanolamine molar ratio to have ZnO films with different trace amounts of starting materials. In addition we also prepared ZnO films annealed at 200 °C for different times (from 5′ to 60′) in order to evaluate this effect on the trace amount removal. © 2014, Springer Science+Business Media New York.

In this work we studied the influence of the annealing treatments of a sol-gel derived ZnO electron transport layer deposited on ITO substrate, on the performances of inverted bulk heterojunction polymer solar cells using a blend of poly[(4,8-bis-(2-ethylhexyloxy)-benzo[1,2-b;4,5-b′]dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiopene)-2,6-diyl] and [6,6]-phenyl C71 butyric acid methyl ester. Since the annealing treatments needed to complete the formation of the solution-processed ZnO film can modify the underlying ITO electrode, we analyzed the performance of the fabricated cells in terms of the properties of ITO and ZnO films. We found a linear relationship between the sheet resistance of the ITO layer and the series resistance of the corresponding device, which strongly influences the fill factor. The best power conversion efficiency (7%) under simulated AM 1.5G illumination of 100 mW/cm2 was achieved for the polymer solar cell fabricated using a ZnO film annealed at 150 °C for only 5 min. Higher annealing temperatures and times increase the sheet resistance of the ITO worsening the device performances. © 2015 Elsevier B.V. All ights reserved.

The structure and thermal properties of a new class of isotactic copolymers of ethylene (E)/4-methyl-1,3-pentadiene (4MPD) with 4MPD content in the range 40–73 mol % and of isotactic poly-1,2-(4-methyl-1,3-pentadiene) (iP4MPD) homopolymer have been analyzed. The copolymers have been synthesized using 1,4-dithiabutanediyl-linked bis(phenolate) titanium complexes as catalyst precursors, activated by methylaluminoxane. Solution 13C NMR analysis reveals the tendency of the catalyst system to produce copolymers with alternating 4MPD/E constitution. All copolymers are crystalline and show melting temperatures in the range 90–100 °C. The samples with nearly equimolar concentration of units crystallize in a new crystalline form because of the alternating constitution. Structural analysis indicates that in this new form the alternating 4MPD-E sequences assume a nearly trans-planar conformation with periodicity c = 5.13 Å and are arranged in a monoclinic unit cell with parameters a = 5.70 Å, b (unique axis) = 14.95 Å, c (chain axis) = 5.13 Å, and β = 114.4°, according to the space group symmetry Pn.

In this work we made a comparative study between the electrical performances of three different electron transport layers (ETLs), used to build inverted polymer solar cells (PSCs). Two different metal oxides are prepared with a solution process: the first one is zinc oxide, prepared by a solgel procedure dissolving zinc acetate and ethanolamine in the 2-methoxyethanol, the second one is titanium oxide, prepared by spin coating a solution of commercial Titanium(IV)-isoproxide in 2-methoxyethanol. The last ETL is an alcohol soluble conjugated polymer: poly[(9,9-bis(3′-(N, N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)](PFN). Inverted PSCs with the configuration glass/ITO/ETL/photoactive layer/MoO3/Ag were realized in order to investigate the performance of different ETL thin films. The photoactive layer was a blend of poly[(4,8-bis-(2-ethylhexyloxy)-benzo[1,2-b;4,5-b′] dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiopene)-2,6-diyl] and [6,6]-phenyl C71 butyric acid methyl ester. The best power conversion efficiency (6.4%) under simulated AM1.5G illumination of 100 mW/cm2, was achieved for the PSCs fabricated using a ZnO and PFN films.

Molecular dynamics simulations were employed in bulk polyisobutylene, to provide a detailed characterization of the methyl dynamics and to examine its relation to the β-relaxation as described by different experimental techniques. The simulation results were compared to new 13C NMR measurements probing methyl motion at temperatures above the glass transition, as well as to lower temperature literature NMR data. It was found that the 13C NMR results, and those for the β-relaxation reported by dielectric relaxation spectroscopy and neutron scattering experiments, can be interpreted on a common basis through a coupling mechanism between methyl rotation and a recently described fast relaxation motion associated with the chain backbone. In addition, a molecular mechanism for the description of the dielectric β-process observed in polyisobutylene is proposed, and investigated by simulations.

Indium tin oxide (ITO) is the most common transparent anode for polymer solar cells (PSCs). The limited flexibility of ITO, the increasing cost of indium and the patterning of ITO with a lot of chemicals, make this material not desirable for the realization of flexible, low-cost and efficient PSCs. Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has been investigated as innovative polymeric material for replacing ITO due to its high transparency, long-term stability and solution process ability. In this work we realized ITO-free polymer solar cells having as active layer a poly[(4,8-bis-(2-ethylhexyloxy)-benzo[1,2-b;4,5-b′]dithiophene)-2, 6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiopene)-2,6-diyl] / [6,6]-phenyl C71 butyric acid methyl ester (PBDTTT-C/[70]PCBM) blend film. The anode was realized using a highly conductive (HC) PEDOT:PSS layer. We studied the performances of this device by means of IV-dark, IV-light, external quantum efficiency and impedance spectroscopy measurements. The performance of the ITO-free device was compared with the corresponding one built using a standard ITO anode. © 2014 AEIT.

The architecture of a polymer solar cell plays a crucial role on its stability because some of the materials used to build the device can suffer from degradation when exposed to air and/or oxygen. In this work we made a comparative study between the standard and the inverted polymer solar cells based on the bulk-heterojunction structure. We realized standard and inverted polymer solar cells using a blend film of poly[(4,8-bis-(2-ethylhexyloxy)- benzo[1,2-b;4,5-b′]dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl) -thieno[3,4-b]thiopene)-2,6-diyl] / [6,6]-phenyl C71 butyric acid methyl ester (PBDTTT-C:[70]PCBM) blend films. In the standard architecture, the transparent indium tin oxide (ITO) electrode is coated with poly-(3,4- ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) and used as a hole collecting electrode, while in an inverted device configuration, the ITO electrode is turned into the electron collecting contact by surface modification with zinc oxide (ZnO). The standard cells sequence is ITO/PEDOT:PSS/PBDTTT-C: [70]PCBM/Ca/Al and the inverted cells one is ITO/ZnO/PBDTTT-C:[70]PCBM/MoO 3/Ag. We studied the electrical behavior (by means of IV-dark and IV-light at different illumination levels and external quantum efficiency measurements) of both kinds of devices in order to investigate the influence of the architecture (standard vs inverted) on the performance of the solar cells. © 2014 AEIT.

In this paper we present the synthesis and characterization of two novel copolymers obtained from a bithiophene unit carrying octylsulfanyl side chains and thienothiophene units substituted with keto (PK) or ester (PE) groups. Their structural, electrochemical and photophysical properties were investigated by gel permeation chromatography (GPC), thermogravimetric analysis (TGA), NMR, UV-visible-NIR spectroscopy, cyclic voltammetry (CV) and atomic force microscopy (AFM). They possess good solubility in common organic solvents, filmability, proneness to form π-stacks, moderate solvatochromism, good thermal stability and low band gap energy. They were tested as donor materials in combination with [70]PCBM (electron acceptor) in bulk-heterojunction polymer solar cells. The geometry of the devices is: glass/ITO/PEDOT:PSS/copolymer:[70]PCBM/Ca/Al. The external quantum efficiency curve of the best device, realized using a blend of PK : [70]PCBM, 1 : 2 weight ratio, shows a broad response from 350 to 1000 nm. The power conversion efficiency under 100 mW cm-2 AM 1.5G illumination is greater than 1%. © 2014 The Royal Society of Chemistry.

In this work, highly conductive anode based on PEDOT:PSS is proposed as substitute of Indio-Tin Oxide (ITO) in flexible solar cells. The anodic conductive polymer was spin coated on a 125 μm thick polyethylene naphthalate (PEN) substrate. The obtained film was characterized in terms of structure and physical- chemical proprieties. The obtained results are very promising and the conductive film will be investigated in future as electrode in a complete polymeric solar cell. © 2014 AIP Publishing LLC.

C2-symmetric group 4 metallocenes based catalysts (rac-[CH2(3-tert-butyl-1-indenyl)2]ZrCl2(1), rac-[CH2(1-indenyl)2]ZrCl2(2) and rac-[CH2(3-tert-butyl-1-indenyl)2]TiCl2(3)) are able to copolymerize styrene and 1,3-butadiene, to give products with high molecular weight. In agreement with symmetry properties of metallocene precatalysts, styrene homosequences are in isotactic arrangements. Full determination of microstructure of copolymers was obtained by 13C NMR and FTIR analysis and it reveals that insertion of butadiene on styrene chain-end happens prevailingly with 1,4-trans configuration. In the butadiene homosequences, using zirconocene-based catalysts, the 1,4-trans arrangement is favored over 1,4-cis, but the latter is prevailing in the presence of titanocene (3). Diad composition analysis of the copolymers makes possible to estimate the reactivity ratios of copolymerization: zirconocenes (1) and (2) produced copolymers having r1 × r2 = 0.5 and 3.0, respectively (where 1 refers to styrene and 2 to butadiene); while titanocene (3) gave tendencially blocky styrene–butadiene copolymers (r1 × r2 = 8.5). The copolymers do not exhibit crystallinity, even when they contain a high molar fraction of styrene. Probably, comonomer homosequences are too short to crystallize (ns = 16, in the copolymer at highest styrene molar fraction). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1476–1487, 2008

The structural transformations occurring in initially homogeneous aqueous solutions of poly(vinyl alcohol) (PVA) through application of freezing (-13 degrees C) and thawing (20 degrees C) cycles is investigated by time resolving small-angle neutron scattering (SANS). These measurements indicate that formation of gels of complex hierarchical structure arises from occurrence of different elementary processes, involving different length and time scales. The fastest process that could be detected by our measurements during the first cryotropic treatment consists of the crystallization of the solvent. However, solvent crystallization is incomplete, and an unfrozen liquid microphase more concentrated in PVA than the initial solution is also formed. Crystallization of PVA takes place inside the unfrozen liquid microphase and is slowed down because of formation of a microgel fraction. Water crystallization takes place in the early 10 min of the treatment of the solution at subzero temperatures, and although below 0 degrees C the PVA solutions used for preparation of cryogels should be below the spinodal curve, occurrence of liquid-liquid phase separation could not be detected in our experiments. Upon thawing, ice crystals melt, and transparent gels are obtained that become opaque in approximately 200 min, due to a slow and progressive increase of the size of microheterogeneities (dilute and dense regions) imprinted during the fast freezing by the crystallization of water. During the permanence of these gels at room temperature (for hours), the presence of a high content of water (higher than 85% by mass) prevents further crystallization of PVA. Crystallization of PVA, in turn, is resumed by freezing the gels at subzero temperatures, after water crystallization and consequent formation of an unfrozen microphase. The kinetic parameters of PVA crystallization during the permanence of these gels at subzero temperatures are the same shown by PVA during the first freezing step of the solutions.

The structure of poly(vinyl alcohol) (PVA) hydrogels formed as a result of freeze/thaw treatments of aqueous solutions of the polymer (11 wt % PVA) in the freshly prepared state is analyzed through the combined use of small (SANS) and ultrasmall (USANS) angle neutron scattering techniques. The structure of these hydrogels may be described in terms of polymer rich regions, with dimensions of the order of 1-2 microm, dispersed in a water rich phase, forming two bicontinuous phases. The PVA chains in the polymer rich phase form a network where the cross-linking points are mainly crystalline aggregates of PVA having average dimensions of approximately 45 A. The structural organization of freeze/thaw PVA hydrogel membranes does not change either after rehydration of dried gels or in the presence of a tensile force. Finally, addition of surfactant micelles inside the gel provides a formulation with both hydrophobic and hydrophilic regions, which demonstrates the potential of the system for drug delivery. Both SANS and EPR measurements show that sodium decylsulfate (C10OS) micelles do not significantly interact with the PVA gel. Variation of the gel structure by the number of freeze/thaw cycles should modulate the rate of release of an active constituent, for example, in a dermal patch.