Space Charge–Limited Current Model for Polymers

Polymers have exceptional charge transport mechanism as a combination of delocalization and localization of charge carriers with intramolecular and intermolecular charge interaction, respectively, and most of the time, it is interpreted with Mott-Gurney space charge–limited current model. As polymers are full of traps, therefore, Mott-Gurney space charge–limited model is modified with various trap distributions as trapped space charge–limited model. The most crucial parameter affected by the nature and distribution of traps is the carrier mobility, and it is argued that space charge–limited model is an acceptable choice for the mobility measurement for polymer. Similarly, in order to account the commonly observed lowering of trap barrier height at higher electric field, the Mott-Gurney space charge–limited current is further modified with little variations, which are evaluated and discussed in detail

Advances in Smart Materials and Applications

This is one of a series of special issues published in Advances in Materials Science and Engineering, focusing on the latest advances of smart materials and their applications. Evolution of engineering materials is strongly depending on the growing transformation of complexity in engineering products. New materials being designed are required to provide specific properties and demonstrate certain functional characteristics by manipulating their dimension, chemistry, and structure through various advanced technologies.Therefore, “smartness” of a material has become the topic of interest. Properties of smart materials may change accordingly to the applied external stimuli. Under the direction of the editorial team, we showcase advances of organic and inorganic based smart materials and their applications in areas of specific interest such as energy, environment, and health. A total of 9 articles are published in this special issue. Six articles are focused on production, synthesis, and optimization of smart materials; and the remaining are dedicated to application of smart materials

Development of Semitransparent UV Photodetector Based on PTB7-Th:PCBM Composite Using the Cost-effective Fabrication Method

This article presents a semitransparent ultraviolet (UV) sandwich-surface type sensor based on PTB7-Th: PCBM composite. The ultraviolet (UV) transparency of 29% was achieved through a cost-effective drop-cast fabrication method. The variation in UV intensity (0 to 20,000 pW/cm2) and frequency (100 Hz, 1 kHz, 10 kHz, 100 kHz, and 200 kHz) was carried out, and variation of impedance and capacitance has been studied. After a comprehensive analysis under specific UV strength and frequency, a considerable increase in capacitance and a significant decrease in impedance were observed. The generation of electron-hole pair relates such findings by increasing the concentration of charges, combined potential, and possible frequency dependence of charge mobility under UV-irradiation. The UV sensor can be used for measuring the UV and visible light intensities. They have applications in the field of electronics and photonics.The authors would like to acknowledge the support of the Higher Education Commission Pakistan, Pakistan Science Foundation, GIK Institute of Engineering Sciences and Technology of Pakistan for providing the necessary research facilities. The authors acknowledge the support of Dr. Rashid Ali for XRD patterns and Dr. Imran Khan for AFM images

Solar Biogas Digester with Built-In Reverse Absorber Heater

In this work the design, fabrication and investigation of a solar biogas digester with built-in RAH (Reverse Absorber Heater) is presented. The maximum temperature (50 o C) inside of the methane tank was taken as a main parameter at the design of the digester. Using energy balance equation for the case of a static mass of fluid being heated; the parameters of thermal insulation of the methane tank were counted. The biogas digester is consisting of methane tank with built-in solar RAH to utilize solar energy for the heating of the slurry prepared from the different organic wastes (dung, sewage, food wastes etc). The methane tank was filled up to 70% of volume by organic wastes of the GIK Institute sewage, firstly, and secondly, by sewage and cow dung as well. During three months (October-December, 2009) and two months (February-March, 2010) the digester was investigated. The solar irradiance incident to the absorber, slurry's temperature and ambient temperature were measured. It was found that using sewage only and sewage with cow dung the retention times was 4 weeks and two weeks respectively and biogas quantity produced was 0.4 and 8.0 m 3 respectively. In addition, biogas upgradation scheme for removal of carbon dioxide, hydrogen sulphide and water vapor from biogas and conversion of biogas energy conversion into electric power is also discussed

A Novel Poly-N-Epoxy Propyl Carbazole Based Memory Device

Generally, polymer-based memory devices store information in a manner distinct from that of silicon-based memory devices. Conventional silicon memory devices store charges as either zero or one for digital information, whereas most polymers store charges by the switching of electrical resistance. For the first time, this study reports that the novel conducting polymer Poly-N-Epoxy-Propyl Carbazole (PEPC) can offer effective memory storage behavior. In the current research, the electrical characterization of a single layer memory device (metal/polymer/metal) using PEPC, with or without doping of charge transfer complexes 7,7,8,8-tetra-cyanoquino-dimethane (TCNQ), was investigated. From the current–voltage characteristics, it was found that PEPC shows memory switching effects in both cases (with or without the TCNQ complex). However, in the presence of TCNQ, the PEPC performs faster memory switching at relatively lower voltage and, therefore, a higher ON and OFF ratio (ION/IOFF ~ 100) was observed. The outcome of this study may help to further understand the memory switching effects of conducting polymer

Flexible organic photo-thermogalvanic cell for low power applications

In this paper, we report an organic semiconductor based flexible thermogalvanic cell for conversion of heat and light energy into electric power. This thermogalvanic cell has been fabricated using a eco-friendly, affordable and commercially available organic material known as an orange dye (C17H17N5O2), which is soluble in water. The thermogalvanic cell consists of a Carbon/aqueous solution of orange dye/Carbon structure. The cell contains a flexible polymer tube casing, filled with a 5 wt% organic semiconductor orange dye aqueous solution and carbon-electrodes. Gradient of temperature (ΔT) up to 28 K was created by low power electric heater and up to 6 K by illumination. It was found that at ΔT = 8 K, the open-circuit voltage (V oc ), short-circuit current (I sc ) and Seebeck coefficient were in the range of −(31–32) mV, −(2.6–2.7) µA and −(3.8–3.9) mV/K, respectively. The thermogalvanic cell holds the promise of potential use in low-power applications (e.g. medical) and temperature gradient measurement.This publication was made possible by PDRA Grant No. PDRA1-0117-14109 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.Scopu

Fabrication and Investigation of Graphite-Flake-Composite-Based Non-Invasive Flex Multi-Functional Force, Acceleration, and Thermal Sensor

This work examines the physics of a non-invasive multi-functional elastic thin-film graphite flake–isoprene sulfone composite sensor. The strain design and electrical characterization of the stretching force, acceleration, and temperature were performed. The rub-in technique was used to fabricate graphite flakes and isoprene sulfone into sensors, which were then analyzed for their morphology using methods such as SEM, AFM, X-ray diffraction, and Fourier transform infrared spectroscopy to examine the device’s surface and structure. Sensor impedance was measured from DC to 200 kHz at up to 20 gf, 20 m/s2, and 26–60 °C. Sensor resistance and impedance to stretching force and acceleration at DC and 200 Hz rose 2.4- and 2.6-fold and 2.01- and 2.06-fold, respectively. Temperature-measuring devices demonstrated 2.65- and 2.8-fold decreases in resistance and impedance at DC and 200 kHz, respectively. First, altering the graphite flake composite particle spacing may modify electronic parameters in the suggested multi-functional sensors under stress and acceleration. Second, the temperature impacts particle and isoprene sulfone properties. Due to their fabrication using an inexpensive deposition technique, these devices are environmentally friendly, are simple to build, and may be used in university research in international poverty-line nations. In scientific laboratories, such devices can be used to teach students how various materials respond to varying environmental circumstances. They may also monitor individuals undergoing physiotherapy and vibrating surfaces in a controlled setting to prevent public health risks.The authors are grateful to UCSI Universiti for funding this research

Fabrication of flexible conductive films by rubbing in technology for application in elastic thermo-electric cells

This method solves the problem of fabrication of flexible elastic conductive thin film samples for thermoelectric applications. For this purpose, rubbing in technology at room temperature condition has been used which is simple, economical and reliable. As a result, elastic thermo-electric cells have been fabricated that can be used for low power applications and for measurement of the gradient of temperature in industry, medicine and in instrumentation as well. The elastic nature of the thermo-electric cells allows us to place the ''hot'' and ''cold'' points of the thermo-electric cells in different planes that make these thermo-electric cells useful for different kind of applications without limitation to place them in a line or in a plane. - 2019 The AuthorsThis work was made possible by PDRA grant # PDRA1-0117-14109 from the Qatar national research fund (a member of Qatar foundation). The findings achieved herein are solely the responsibility of the author(s).Scopu