4,366 research outputs found

    Inexpensive Measuring System for the Characterization of Organic Transistors

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    [EN] A measuring module has been specifically designed for the electrical characterization of organic semiconductor devices such as organic field effect transistors (OFETs) and organic electrochemical transistors (OECTs) according to the IEEE 1620-2008 standard. This device has been tested with OFETs based on 6,13-bis(triisopropylsilylethinyl) pentacene (TIPS-pentacene). The measuring system has been constructed using a NI-PXIe-1073 chassis with integrated controller and two NI-PXI-4132 programmable high-precision source measure units (SMUs) that offer a four-quadrant +/- 100V output, with resolution down to 10 pA. LabVIEW (TM) has been used to develop the appropriate program. Most of the main OFET parameters included in the IEEE 1620 standard can be measured by means of this device. Although nowadays expensive devices for the characterization of Si-based transistors are available, devices for the characterization of organic transistors are not yet widespread in the market. Fabrication of a specific and flexible module that can be used to characterize this type of transistors would provide a powerful tool to researchers.All financial support from the Spanish Government and FEDER funds (MAT2015-64139-C4-3-R (MINECO/FEDER)) and the Generalitat Valenciana (GVA funds) (AICO/2015/103) is gratefully acknowledged.Pérez Fuster, C.; Lidon-Roger, JV.; Contat-Rodrigo, L.; Garcia-Breijo, E. (2018). Inexpensive Measuring System for the Characterization of Organic Transistors. Journal of Sensors. 2018:1-9. https://doi.org/10.1155/2018/4286894S19201

    Organic small molecules semiconductors as direct X-ray detectors

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    Organic small molecules semiconductors are promising in the field of direct ionizing radiation detection. Unlike their inorganic counterpart, these molecules are easy to work with, since they are flexible, soluble and can be deposited on electronic devices with very simple processes, such as drop-casting and spin-casting. Moreover, these materials have good detection properties and very low working voltage. To this day, organic semiconductors have mainly been used in indirect radiation detection, employed both in scintillator and as photodetectors. However, direct detection of ionizing radiation is a far more effective method, since it is performed within a single material and a single conversion, directly from photons to electrical signal; furthermore, it provides a higher signal-to-noise ratio and a faster response time. In this experimental work, I fabricated four direct detectors based on transistors; two different organic solutions were drop-casted onto the transistors, creating a conduction channel between source and drain electrodes. Both these solutions had chlorobenzene as a solvent, with DiF-TES-ADT and DiF-TEG-ADT as solutes, respectively, in a 0.5% concentration. The purpose of this thesis is dual. Firstly, I want to study how the detectors’ sensitivity is influenced by semiconductor molecules with different Z-number; secondly, I want to test a new drop-casting method (SAC method) and compare it to results previously obtained with traditional deposition methods. The results are very promising, with very high values of sensitivity obtained with low voltages

    Value-added Synthesis of Graphene: Recycling Industrial Carbon Waste into Electrodes for High-Performance Electronic Devices

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    We have developed a simple, scalable, transfer-free, ecologically sustainable, value-added method to convert inexpensive coal tar pitch to patterned graphene films directly on device substrates. The method, which does not require an additional transfer process, enables direct growth of graphene films on device substrates in large area. To demonstrate the practical applications of the graphene films, we used the patterned graphene grown on a dielectric substrate directly as electrodes of bottom-contact pentacene field-effect transistors (max. field effect mobility similar to 0.36 cm(2).V-1.s(-1)), without using any physical transfer process. This use of a chemical waste product as a solid carbon source instead of commonly used explosive hydrocarbon gas sources for graphene synthesis has the dual benefits of converting the waste to a valuable product, and reducing pollution.111714Ysciescopu

    Charge-transfer induced surface conductivity for a copper based inorganic-organic hybrid

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    Inorganic-organic hybrids are receiving increasing attention as they offer the opportunity to combine the robust properties of inorganic materials with the versatility of organic compounds. We have studied the electric properties of an inorganic-organic hybrid with the chemical formula: CuCl4(C6H5CH2CH2NH3)2. This material is a ferromagnetic insulator that can easily be processed from solution. We show that the surface conductivity of the hybrid can be increased by five orders of magnitude by covering the surface with an organic electron donor. This constitutes a novel method to dope perovskite-based materials and study their charge transport properties.

    Advanced Materials for Organic Photonics

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    V oblasti nových nízkomolekulárních organických materiálů patří deriváty difenyldiketopyrrolopyrrolu (DPP), používané dříve jako barviva a pigmenty, k objektům vysokého zájmu pro jejich potencionální aplikace v moderních technologiích. Studium jejich optických vlastností ve vztahu k jejich chemické struktuře umožní využití jejich vysokého potenciálu ve vývoji pokročilých inteligentních materiálů. Přehled chemických a fyzikálních vlastností DPP derivátů a zhodnocení současného stavu řešené problematiky jsou uvedeny v teoretické části této práce. Tři hlavní procesy studované v této práci jsou: klasická absorpce a emise, dvoufotonová absorpce (TPA) a zesílená spontánní emise (ASE). Výsledky budou diskutovány a shrnuty ve dvou částech: první zahrnuje první dvě výše zmíněné oblasti a druhá problematiku zesílené spontánní emise.Among low molecular organic materials, diphenyl-diketo-pyrrolopyrrole (DPP) derivatives used earlier as dyes are of high interest in modern technologies. The study of their optical properties related to their chemical structure will provide more information on the later relationship and comfort the high potential of DPP derivatives in the making of more performant smart materials. An overview of their chemical and physical properties is described in the theoretical part and followed by the state of the art in the field of interest concerning this thesis. The three main processes studied in this work are: The classic absorption and emission, the two photon absorption (TPA) and the amplified spontaneous emission (ASE). The results will be discussed and summarized in two parts: The first concerning the one and the two photon absorption and the second the amplified spontaneous emission.

    Light Generation and Harvesting in a Van der Waals Heterostructure

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    Two-dimensional (2D) materials are a new type of materials under intense study because of their interesting physical properties and wide range of potential applications from nanoelectronics to sensing and photonics. Monolayers of semiconducting transition metal dichalcogenides MoS2 or WSe2 have been proposed as promising channel materials for field-effect transistors (FETs). Their high mechanical flexibility, stability and quality coupled with potentially inexpensive production methods offer potential advantages compared to organic and crystalline bulk semiconductors. Due to quantum mechanical confinement, the band gap in monolayer MoS2 is direct in nature, leading to a strong interaction with light that can be exploited for building phototransistors and ultrasensitive photodetectors. Here, we report on the realization of light-emitting diodes based on vertical heterojunctions composed of n-type monolayer MoS2 and p-type silicon. Careful interface engineering allows us to realize diodes showing rectification and light emission from the entire surface of the heterojunction. Electroluminescence spectra show clear signs of direct excitons related to the optical transitions between the conduction and valence bands. Our pn diodes can also operate as solar cells, with typical external quantum efficiency exceeding 4%. Our work opens up the way to more sophisticated optoelectronic devices such as lasers and heterostructure solar cells based on hybrids of two-dimensional (2D) semiconductors and silicon.Comment: Submitted versio

    Organic Single-Crystal Field-Effect Transistors

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    We present an overview of recent studies of the charge transport in the field effect transistors on the surface of single crystals of organic low-molecular-weight materials. We first discuss in detail the technological progress that has made these investigations possible. Particular attention is devoted to the growth and characterization of single crystals of organic materials and to different techniques that have been developed for device fabrication. We then concentrate on the measurements of the electrical characteristics. In most cases, these characteristics are highly reproducible and demonstrate the quality of the single crystal transistors. Particularly noticeable are the small sub-threshold slope, the non-monotonic temperature dependence of the mobility, and its weak dependence on the gate voltage. In the best rubrene transistors, room-temperature values of μ\mu as high as 15 cm2^2/Vs have been observed. This represents an order-of-magnitude increase with respect to the highest mobility previously reported for organic thin film transistors. In addition, the highest-quality single-crystal devices exhibit a significant anisotropy of the conduction properties with respect to the crystallographic direction. These observations indicate that the field effect transistors fabricated on single crystals are suitable for the study of the \textit{intrinsic} electronic properties of organic molecular semiconductors. We conclude by indicating some directions in which near-future work should focus to progress further in this rapidly evolving area of research.Comment: Review article, to appear in special issue of Phys. Stat. Sol. on organic semiconductor
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