1,721,025 research outputs found
High-Performance UV–Vis–NIR Phototransistors Based on Single-Crystalline Organic Semiconductor–Gold Hybrid Nanomaterials
No full textHybrid materials in optoelectronic devices can generate new functionality or provide synergistic effects that enhance the properties of each component. Here, high-performance phototransistors with broad spectral responsivity in UV-vis-near-infrared (NIR) regions, using gold nanorods (Au NRs)-decorated n-type organic semiconductor and N, N'-bis(2-phenylethyl)-perylene-3,4: 9,10-tetracarboxylic diimide (BPE-PTCDI) nanowires (NWs) are reported. By way of the synergistic effect of the excellent photo-conducting characteristics of single-crystalline BPE-PTCDI NW and the light scattering and localized surface plasmon resonances (LSPR) of Au NRs, the hybrid system provides new photodetectivity in the NIR spectral region. In the UV-vis region, hybrid nanomaterial- based phototransistors exhibit significantly enhanced photo-responsive properties with a photo-responsivity (R) of 7.70 x 10(5) A W-1 and external quantum efficiency (EQE) of 1.42 x 108% at the minimum light intensity of 2.5 mu W cm(-2), which are at least tenfold greater than those of pristine BPE-PTCDI NW-based ones and comparable to those of high-performance inorganic material-based devices. While a pristine BPE-PTCDI NW-based photodetector is insensitive to the NIR spectral region, the hybrid NW-based phototransistor shows an R of 10.7 A W-1 and EQE of 1.35 x 10(3)% under 980 nm wavelength-NIR illumination. This work demonstrates a viable approach to high-performance photo-detecting systems with broad spectral responsivity.112112sciescopu
Tuning polarity and improving charge transport in organic semiconductors
No full textAlthough state-of-the-art ambipolar polymer semiconductors have been extensively reported in recent years, high-performance ambipolar polymers with tunable dominant polarity are still required to realize on-demand, target-specific, high-performance organic circuitry. Herein, dithienyl-diketopyrrolopyrrole (TDPP)-based polymer semiconductors with engineered side-chains have been synthesized, characterized and employed in ambipolar organic field-effect transistors, in order to achieve controllable and improved electrical properties. Thermally removable tert-butoxycarbonyl (t-BOC) groups and hybrid siloxane-solubilizing groups are introduced as the solubilizing groups, and they are found to enable the tunable dominant polarity and the enhanced ambipolar performance, respectively. Such outstanding performance based on our molecular design strategies makes these ambipolar polymer semiconductors highly promising for low-cost, large-area, and flexible electronics.110sciescopu
A Role of Side-Chain Regiochemistry of Thienylene–Vinylene–Thienylene (TVT) in the Transistor Performance of Isomeric Polymers
No full textThe pi-extended (E)-2-(2-(thiophen-2-ye-vinyl)thiophene (TVT)-based polymers are an interesting class of semiconducting polymers because of their excellent mobilities and unique film microstructures. Despite these properties, the effect of the side-chain regiochemistry of TVT skeletons on the intrinsic properties of these polymers remains unclear. To investigate this, in this study, hexyl-substituted TVT subunits with a "tail in (TI)" or "tail out (TO)" regiosymmetrical arrangement were first introduced into diketo-pyrrolopyrrole (DPP) -based copolymer main chains to afford "isomeric" polymers PI and PO, respectively. By combining optical spectroscopy, atomic force microscopy (AFM), and grazing incidence X-ray diffraction (GIXD) data, we quantitatively characterized the aggregation, crystallization, and backbone orientation of both polymer films, which were then correlated to the charge carrier mobilities. The PI film exhibited a bimodal packing motif comprising a mixture of edge-on and face-on orientations, which was beneficial for three-dimensional (3D) charge transport and resulted in a hole mobility 2-fold larger than that in the PO film (mu(h) = 1.69 cm(2) V-1 s(-1)). This comparative study substantiates the important role of the regiochemistry of TVT in developing high-performance semiconducting polymers.11125sciescopu
Recent progress in large sized & high performance organic TFT array
No full textRecently, we have developed 15.0 inch XGA organic TFT array and its LCD module, which might be world-largest array size and highest resolution in organic based device. This achievement is to be combined with several technical breakthroughs include new organic gate dielectric material, novel ohmic contact technique, and well-optimized process-architectures. Base on the newly developed organic gate dielectric with pentacene, we have obtained world-record field effect TFT mobilities in excess of 7cm2/Vsec and excellent on/off ratios as ∼106. For jumping up the OTFT research activities from laboratory scale to real production line, we have developed two key technologies. One is the new ohmic contact process with very common materials in the current LCD manufacturing such as ITO; the bottom contact structured OTFT with ITO source-drain electrode shows much the same performances as that with gold source-drain electrode. The other key technology to realize the large size organic device is that of optimizing the array structure to minimize the OTFT performance degradations. By combining these novel technologies, a 15.0" XGA prototype LCD panel is fabricated and shows good display performance.11scopu
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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