Papers by Keyword: Organic Semiconductors

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Authors: Pejman Shabani, Farhad Akbari Boroumand, Faramarz Hossein-Babaei
Abstract: Poly [2-methoxy, 5-(2¢-ethyl-hexyloxy)-p-phenylene-vinylene] (MEH-PPV) is a well known hole-conducting semiconductor utilized in the fabrication of optoelectronic devices because of its interesting electroluminescence. However, both electroluminescence and electrical conduction in this material sharply deteriorate upon exposure to oxygen, necessitating fabrication and hermetic sealing of the MEH-PPV-based devices in oxygen-free environments. Same shortcoming has excluded the material from applications requiring air exposure. We have recently presented a model for the oxidation mechanism of an MEH-PPV layer and have shown that such layers, after oxidation at certain conditions, can support air-stable electrical conduction. Here, we describe the experimental conditions required for the preparation of an oxidized MEHPPV layer, and provide experimental data on the stability of such layers at different conditions. It is shown that the fabricated air-stable oxidized MEH-PPV layers are excellent for a number of chemical sensor applications.
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Authors: Jatinder V. Yakhmi, Vaishali Bambole
Abstract: The emergence of spintronics (spin-based electronics), which exploits electronic charge as well as the spin degree of freedom to store/process data has already seen some of its fundamental results turned into actual devices during the last decade. Information encoded in spins persists even when the device is switched off; it can be manipulated with and without using magnetic fields and can be written using little energy. Eventually, spintronics aims at spin control of electrical properties (I-V characteristics), contrary to the common process of controlling the magnetization (spins) via application of electrical field. In the meantime, another revolution in electronics appears to be unfolding, with the evolution of Molecular Spintronics which aims at manipulating spins and charges in electronic devices containing one or more molecules, because a long spin lifetime is expected from the very small spin-orbit coupling in organic semiconductors. This futuristic area is fascinating because it promises the integration of memory and logic functions,
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Authors: Gao Yu Zhong, Pei Yuan Fang, Yong Ming Cao
Abstract: A series of organic light-emitting diodes (OLEDs) with or without a bathocuproine (BCP) layer inserted in the control device indium-tin-oxide (ITO)\ N,N'-bis-(1-naphthl)-diphenyl-1,1'- biphenyl-4,4'-diamine (NPB)\ tris(8-quinolinolato) aluminum (Alq)\LiF\Al have been fabricated and measured. Different influences of the BCP layer on electroluminescence (EL) of the OLEDs have been investigated. It is found that the highest efficiency of the OLED with a 1-nm BCP layer inserted between NPB and Alq increases to 3.99 cd/A, ~48% higher than that of the control device, while the EL efficiencies of the devices with other structures are similar to the latter. This phenomenon is ascribed to the hole-blocking effect of the BCP layer and the resulting higher density of carriers in the emission zone of the OLED. The EL performances of the OLEDs with different thicknesses of BCP layer are also discussed in details.
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Authors: Beynor Antonio Paez-Sierra, Fredy Mesa, Anderson Dussan
Abstract: Engineering, stability and orientation of semiconducting molecules are necessary to achieve the high efficiency of multifunctional organic-based devices. Several conjugated molecules facilitate the use of external magnetic fields to tailor both their molecular orientation and electronic properties while being processed for bio or opto-electronic applications. In this work, molecular thin films of vanadyl phthalocynine (VOPc) layers forming conducting channels in organic field-effect transistors were investigated. Three systems based on 100 nm thick VOPc thin film were grown, one in absence of magnetic field, while the other two with parallel and perpendicular to the substrate plane, respectively. Devices were ex-situ investigated by electrical characterization and confocal scanning Raman spectroscopy (SRS). All molecular layers growth on Au electrodes presented enhancement of the Raman signal.
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Authors: Eun Hee Lim
Abstract: The effect of substitution pattern of the linear-type π-conjugated oligothiophenes is examined. The material solubility, thermal properties, and charge transport characteristics of two hexyl subsituted quinquethiophenes (DH5T) were determined along with the characteristics of an organic field-effect transistor (OFET). The solubility of 4,7-bis (3’-hexyl-2,2’-bithiophene-5-yl) thiophene (β-DH5T), which featured a lateral substitution, was significantly better than that of α,α’-dihexylquinquethiophene (α-DH5T) by altering the directional position of the alkyl group, which makes it a good candidate for solution-processed OFETs. Despite the well-defined vertical alignment of α-DH5T, the hole mobility of the β-DH5T film (3.02 × 103 cm2 V–1 s–1) was one order of magnitude higher than the hole mobility of the α-DH5T film (2.47 × 104 cm2 V–1 s–1) prepared by solution processing.
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