196,698 research outputs found
FLEXIBLE THERMOELECTRIC MICROGENERATOR AND PRODUCTION METHOD THEREOF
No full textThe present invention relates to a thermoelectric microgenerator (1) and to a method for the production thereof, wherein said thermoelectric microgenerator (1) comprises a flexible supporting substrate (10) for a plurality of thermoelectric elements (20), perforated with a plurality of through holes (12) in the supporting substrate (10) filled with thermoelectric material (21)
Multi-length-scale relationships between the polymer molecular structure and charge transport: the case of poly-naphthalene diimide bithiophene
No full textCharge transport in organic polymer semiconductors is a complex phenomenon affected by structural and electronic properties ranging over different length scales, from the molecular one up to the macro-scale. Charge carriers show markers of spatial localization (polarons), and drift for distances from a few to 100 mm in typical field-effect devices. Being sensitive to such different length scales, field-effect mobility is evidently a figure of merit that averages local properties at the molecular scale, over distances orders of magnitude larger. Understanding charge transfer processes at each length scale is consequently of paramount importance. To fulfill this aim, a multi-length-scale approach, encompassing experimental and theoretical modeling investigations, has to be built. Here we critically revise a series of experimental and theoretical tools that can contribute to develop a consistent multi-scale investigation methodology. We consider them within the study of an exemplary, good electron transporting naphthalene-diimide bi-thiophene copolymer, which has represented a breakthrough for the class of n-type polymers since its disclosure in 2009
Charge Injection in Solution-Processed Organic Field-Effect Transistors: Physics, Models and Characterization Methods
No full textA high-mobility organic semiconductor employed as the active material in a field-effect transistor does not guarantee per se that expectations of high performance are fulfilled. This is even truer if a downscaled, short channel is adopted. Only if contacts are able to provide the device with as much charge as it needs, with a negligible voltage drop across them, then high expectations can turn into high performances. It is a fact that this is not always the case in the field of organic electronics.
In this review, we aim to offer a comprehensive overview on the subject of current injection in organic thin film transistors: physical principles concerning energy level (mis)alignment at interfaces, models describing charge injection, technologies for interface tuning, and techniques for characterizing devices. Finally, a survey of the most recent accomplishments in the field is given. Principles are described in general, but the technologies and survey emphasis is on solution processed transistors, because it is our opinion that scalable, roll-to-roll printing processing is one, if not the brightest, possible scenario for the future of organic electronics.
With the exception of electrolyte-gated organic transistors, where impressively low width normalized resistances were reported (in the range of 10 Ω·cm), to date the lowest values reported for devices where the semiconductor is solution-processed and where the most common architectures are adopted, are ∼10 kΩ·cm for transistors with a field effect mobility in the 0.1–1 cm2/Vs range. Although these values represent the best case, they still pose a severe limitation for downscaling the channel lengths below a few micrometers, necessary for increasing the device switching speed. Moreover, techniques to lower contact resistances have been often developed on a case-by-case basis, depending on the materials, architecture and processing techniques. The lack of a standard strategy has hampered the progress of the field for a long time. Only recently, as the understanding of the rather complex physical processes at the metal/semiconductor interfaces has improved, more general approaches, with a validity that extends to several materials, are being proposed and successfully tested in the literature. Only a combined scientific and technological effort, on the one side to fully understand contact phenomena and on the other to completely master the tailoring of interfaces, will enable the development of advanced organic electronics applications and their widespread adoption in low-cost, large-area printed circuits
MONOREDUCED [M(R,R’timdt)2]- DITHIOLENES (M = Ni, Pd, Pt; R,R’timdt = DISUBSTITUTED IMIDAZOLINE-2,4,5-TRITHIONE): SOLID STATE PHOTOCONDUCTING PROPERTIES IN THE THIRD OPTICAL FIBER WINDOW
No full textElectrochemically monoreduced [M(R,R’timdt)2] dithiolenes, showing unprecedented wavelength
selective photoconducting properties in the third optical fiber window (1500–1800 nm), finetunable through modifications in the chemical structure, allowed for the fabrication of a test photodetector with a bit rate of about 85 kbit s-1
Atomistic Simulations of P(NDI2OD-T2) Morphologies: From Single Chain to Condensed Phases
No full textWe investigate theoretically the structure, crystallinity, and solubility of a high-mobility n-type semiconducting copolymer, P(NDI2OD-T2), and we propose a set of new force field parameters. The force field is reparametrized against density functional theory (DFT) calculations, with the aim to reproduce the correct torsional angles that govern the polymer chain flexibility and morphology. We simulate P(NDI2OD-T2) oligomers in different environments, namely, in vacuo, in the bulk phase, and in liquid toluene and chloronaphthalene solution. The choice of these solvents is motivated by the fact that they induce different kinds of molecular preaggregates during the casting procedures, resulting in variable device performances. Our results are in good agreement with the available experimental data; the polymer bulk structure, in which the chains are quite planar, is correcly reproduced, yet the isolated chains are flexible enough to fold in vacuo. We also calculate the solubility of P(NDI2OD-T2) in toluene and chloronaphthalene, predicting a much better solubility of the polymer in the latter, also in accordance to experimental observations. Different morphologies and dynamics of the oligomers in the two solvents have been observed. The proposed parameters make it possible to obtain the description of P(NDI2OD-T2) in different environments and can serve as a basis for extensive studies of this polymer semiconductor, such as, for example, the dynamics of aggregation in solvent
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