1,721,004 research outputs found
Effect of Electron-Acceptor Content on the Efficiency of Regioregular Double-Cable Thiophene Copolymers in Single-Material Organic Solar Cells
No full textABSTRACT: Three regioregular thiophenic copolymers, characterized by a bromine atom or a C60-fullerene group at different molar ratios at the end of a decamethylenic plastifying side chain, have been successfully synthesized using a straightforward postpolymerization functionalization procedure based on a Grignard coupling reaction. Owing to their good solubility in common organic solvents, the products were fully characterized using chromatographic, spectroscopic, thermal, and morphological techniques and used as single materials in the photoactive layers of organic solar cells. The photoconversion efficiencies obtained with copolymers were compared with those of a reference cell prepared using a physical blend of the precursor homopolymer and [6,6]-phenyl-C61- butyric acid methyl ester. The best results were obtained with COP2, the copolymer with a 21% molar content of C60- functionalized side chains. The use of the double-cable polymer made possible an enhanced control on the nanomorphology of the active blend, thus reducing phase-segregation phenomena as well as the macroscale separation between the electronacceptor and -donor components, yielding a power conversion efficiency higher than that of the reference cell (4.05 vs 3.68%). Moreover, the presence of the halogen group was exploited for the photo-cross-linking of the active layer immediately after the thermal annealing procedure. The cross-linked samples showed an increased stability over time, leading to good efficiencies even after 120 h of accelerated aging: this was a key feature for the widespread practical applicability of the prepared devices
Developing strategies to optimize the anchorage [Mechanical Properties]
No full text<p>Developing strategies to optimize the anchorage [Mechanical Properties]</p>
Effect of the incorporation of an Ag nanoparticle interlayer on the photovoltaic performance of green bulk heterojunction water-soluble polythiophene solar cells
No full textTwo water-soluble regioregular poly(3-alkylthiophene)s, incorporating aminic groups at the end of the side chains, have been synthesized using a post-polymerization functionalization procedure on a ω-bromine substituted polyalkylthiophene. The high solubility of the obtained polymers in water allowed for the preparation of “green” bulk heterojunction solar cells which reached a power conversion efficiency of 4.85% when PC61BM was used as electron-acceptor material. Improved optical absorption and photocurrent have been obtained by interposing a layer of Ag nanoparticles between the buffer and the photoactive layer, leading to a final power conversion efficiency of 5.51%
Electrospun Polyaniline-Based Composite Nanofibers: Tuning the Electrical Conductivity by Tailoring the Structure of Thiol-Protected Metal Nanoparticles
Full text linkComposite nanofibers made of a polyaniline-based polymer blend and different thiol-capped metal nanoparticles were prepared using ex situ synthesis and electrospinning technique. The effects of the nanoparticle composition and chemical structure on the electrical properties of the nanocomposites were investigated. This study confirmed that Brust’s procedure is an effective method for the synthesis of sub-10 nm silver, gold, and silver-gold alloy nanoparticles protected with different types of thiols. Electron microscopy results demonstrated that electrospinning is a valuable technique for the production of composite nanofibers with similar morphology and revealed that nanofillers are well-dispersed into the polymer matrix. X-ray diffraction tests proved the lack of a significant influence of the nanoparticle chemical structure on the polyaniline chain arrangement. However, the introduction of conductive nanofillers in the polymer matrix influences the charge transport noticeably improving electrical conductivity. The enhancement of electrical properties is mediated by the nanoparticle capping layer structure. The metal nanoparticle core composition is a key parameter, which exerted a significant influence on the conductivity of the nanocomposites. These results prove that the proposed method can be used to tune the electrical properties of nanocomposites.</jats:p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
PROCESSO PER IL TRATTAMENTO DI UN MATERIALE CONTENENTE AMIANTO
No full textIl brevetto descrive il processo biotecnologico in grado di denaturare le fibre di amianto presenti in manufatti cementizi, utilizzando siero di latte esausto
A new photocrosslinkable oligothiophene for organic solar cells with enhanced stability
No full textA novel thiophenic tetramer containing a cinnamate group in the side chain with a functionalization degree of 50% is reported. The tetramer was obtained by means of a simple and straightforward procedure involving the functionalization of a p-methoxyphenoxy substituted thiophenic precursor, which led to a soluble product with a good yield. The oligomer was fully characterized from a structural and chemical point of view and employed for the fabrication of small molecule organic solar cells exploiting the bulk heterojunction (BHJ) architecture. The presence of an UV-light sensitive group in the tetramer allowed the photocrosslinking of tetramer/PCBM blends, giving high values of photocurrent and conversion efficiency for the exposed samples. Moreover, the UV-treated devices showed improved stability, even upon heating for three days at 130 °C, thus confirming that photocrosslinking can strongly reduce phase segregation under severe operational conditions
ELETTRODEPOSIZIONE DI IDROSSIAPATITE NANOMETRICA SU IMPIANTI PROTESICI E PROCESSO ELETTROLITICO PER LA SUA REALIZZAZIONE
No full textLa presente invenzione riguarda un processo per
rivestire una superficie di un elemento metallico con un
coating a base di idrossiapatite biomimetica e
nanometrica, che comprende i seguenti passaggi:
a) predisporre un bagno elettrolitico comprendente
almeno ioni calcio e ioni fosfato ad una temperatura
compresa tra 5°C e 40°C; b) immergere in detto bagno elettrolitico almeno un catodo ed almeno un anodo, detto almeno un catodo
comprendendo l'elemento metallico da rivestire; c) far passare corrente elettrica continua attraverso detto bagno elettrolitico così da ottenere su detta superficie una deposizione elettrolitica di un composto calcio-fosfato comprendente cristalli nanometrici di
idrossiapatite; d) sottoporre l’elemento metallico rivestito del
composto calcio-fosfato ad un trattamento termico ad una
temperatura compresa tra 70°C e 800°C.
Tale processo consente di ottenere un dispositivo protesico ricoperto con un rivestimento a base di idrossiapatite che aderisce perfettamente alla superficie della protesi e ne permette una completa osteointegrazione.
Electrospun poly(3-hexylthiophene)/poly(ethylene oxide)/graphene oxide composite nanofibers: Effects of graphene oxide reduction
No full textIn this article, we report on the production by electrospinning of P3HT/PEO, P3HT/PEO/GO, and P3HT/PEO/rGO nanofibers in which the filler is homogeneously dispersed and parallel oriented along the fibers axis. The effect of nanofillers' presence inside nanofibers and GO reduction was studied, in order to reveal the influence of the new hierarchical structure on the electrical conductivity and mechanical properties. An in-depth characterization of the purity and regioregularity of the starting P3HT as well as the morphology and chemical structure of GO and rGO was carried out. The morphology of the electrospun nanofibers was examined by both scanning and transmission electron microscopy. The fibrous nanocomposites are also characterized by differential scanning calorimetry to investigate their chemical structure and polymer chains arrangements. Finally, the electrical conductivity of the electrospun fibers and the elastic modulus of the single fibers are evaluated using a four-point probe method and atomic force microscopy nanoindentation, respectively. The electrospun materials crystallinity as well as the elastic modulus increase with the addition of the nanofillers while the electrical conductivity is positively influenced by the GO reduction
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