Current Issue : July - September Volume : 2014 Issue Number : 3 Articles : 4 Articles
Carrier transport properties of organic field effect transistors in\ndinaphtho[2,3-b:2'',3''-f]thieno[3,2-b]thiophene single crystals have been investigated under\nhigh pressure. In contrast to the typical pressure effect of monotonic increase in charge\ntransfer rates according to the application of external hydrostatic pressure, it is clarified\nthat the present organic semiconductor devices exhibit nonmonotonic pressure response,\nsuch as negative pressure effect. X-ray diffraction analysis under high pressure reveals that\non-site molecular orientation and displacement in the heteroacene molecule is assumed to\nbe the origin for the anomalous pressure effects....
Organic light emitting diodes (OLEDs) have attracted much attention in recent\nyears as next generation lighting and displays, due to their many advantages, including\nsuperb performance, mechanical flexibility, ease of fabrication, chemical versatility, etc.\nIn order to fully realize the highly flexible features, reduce the cost and further improve the\nperformance of OLED devices, replacing the conventional indium tin oxide with better\nalternative transparent conducting electrodes (TCEs) is a crucial step. In this review, we\nfocus on the emerging alternative TCE materials for OLED applications, including carbon\nnanotubes (CNTs), metallic nanowires, conductive polymers and graphene. These\nmaterials are selected, because they have been applied as transparent electrodes for OLED\ndevices and achieved reasonably good performance or even higher device performance\nthan that of indium tin oxide (ITO) glass. Various electrode modification techniques and\ntheir effects on the device performance are presented. The effects of new TCEs on light\nextraction, device performance and reliability are discussed. Highly flexible, stretchable\nand efficient OLED devices are achieved based on these alternative TCEs. These results\nare summarized for each material. The advantages and current challenges of these TCE\nmaterials are also identified....
Aminiaturized bandpass filter (BPF) using defected ground structure (DGS) resonatorwith the characteristic of harmonic rejection\nis developed in this paper. The second and third harmonics of the proposed BPF are rejected by the characteristic of steppedimpedance\nDGS resonator. Moreover, open stubs are established so that two adjustable transmission zeros can independently be\ncreated to extend the stopband and improve the rejection level. Finally, a second-order BPF, centered at 1.62GHz with a stopband\nextended up to 5.6GHz and a rejection level better than 20 dB, is designed and implemented for GPS application. A good agreement\nbetween simulation and measurement verifies the validity of this design methodology....
This study proposes three new sinusoidal oscillators based on an operational transresistance amplifier (OTRA). Each of the\nproposed oscillator circuits consists of one OTRA combined with a few passive components. The first circuit is an OTRA-based\nminimum RC oscillator. The second circuit is capable of providing independent control on the condition of oscillation without\naffecting the oscillation frequency. The third circuit exhibits independent control of oscillation frequency through a capacitor. This\nstudy first introduces the OTRA and the related formulations of the proposed oscillator circuits, and then discusses the nonideal\neffects, sensitivity analyses, and frequency stability of the presented circuits. The proposed oscillators exhibit low sensitivities and\ngood frequency stability. Because the presented circuits feature low impedance output, they can be connected directly to the next\nstage without cascading additional voltage buffers. HSPICE simulations and experimental results confirm the feasibility of the new\noscillator circuits....
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