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PublicationCharacterization of doped ZnO thin film for Ammonia gas sensing application(Institute of Physics, Polish Academy of Sciences, 2023)This paper reports on the characterization of Sn- and Al-doped zinc oxide thin film for potential ammonia gas detection. The sol–gel method has been used to deposit the dopant onto the glass substrate at an annealing temperature of 500◦C for three different doping concentrations, which are 0.5, 1.0, and 1.5 at.%. The method used to produce this thin film is sol–gel, as it is cheap, easy, and can be employed at low temperatures. The studies involve the investigation of the morphological structures and electrical and optical properties of doped ZnO. In terms of structural properties, scanning electron microscope images of Sn- and Al-doped ZnO change as the dopant concentration is increased. The doped thin film response and recovery towards 200 ppm of ammonia were observed and recorded. Both dopants show good gas sensing response. The recorded resistance reading suggests that Al is the superior dopant in gas sensing as it produces a low resistance reading of 230 Ω as opposed to 140 kΩ produced by Sn-doped ZnO thin film.
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PublicationA sight of view on electrical impacts, structural properties and surface roughness of tungsten trioxide thin film: effect of substrate temperatures in WO₃/Si device fabrication(IOP Publishing, 2023)Monoclinic WO₃ thin films have been effectively deposited by a simple spray pyrolysis technique at a molar concentration of 0.01 M on a glass substrate in the temperature range of 473 to 673 K. These WO₃ films were used as an interlayer between the metal and the semiconductor, which formed the basic structure of the photodetector. Effect of substrate temperature on WO₃ films during the process of the deposition was systematically interpreted with respect to the structural, morphological, optical and electrical properties of the WO₃ films. The x-ray diffraction pattern revealed the polycrystalline nature of the prepared films with monoclinic phases. At the substrate temperature of 623 K, the nano-thin films were strongly bonded to each other as observed from the FE-SEM images. Visible and ultraviolet spectroscopies indicated the band gap (Eg) of the WO₃ thin film is 3.30 eV. The dc electrical study recorded a sharp increase in the electrical conductivity of the prepared film at substrate temperature of 623 K for tungsten trioxide. It is worth noting that all diodes showed a positive photoresponse under illumination. In particular, the photodetector with the thickness of 300 nm showed higher responsivity 0.02 A/W and detection specificity 8.29 × 1010 Jones.
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PublicationReview—Charge carrier mobility of organic thin film transistor: intrinsic and extrinsic influencing factors based on organic semiconducting materials(IOP Publishing, 2023)The use of organic thin film transistors (OTFTs) is growing rapidly as an alternative to their inorganic counterparts due to their advantageous properties, such as easy processing and flexibility. The performance of OTFTs is still undergoing improvement and taking this as a recognition, this paper reviews various factors that influence the performance of the OTFTs, primarily in terms of field-effect mobility. The influencing factors reviewed in this article are divided into intrinsic and extrinsic factors for different organic semiconducting materials (OSMs). The intrinsic factors include the OSMs’ molecular orientation, OSM/dielectric interaction, and OSM/electrode interaction. The extrinsic factors are basically related to the OSM processing and OTFTs fabrication. For example, the article discusses how mixing, blending, and annealing affect the properties of the OSMs. The effect of the ambient atmosphere on OTFTs’ performance is also discussed. The aim of this article is to discuss the current trends related to one of the critical figures of merit of OTFTs, which is the mobility of charge carriers.
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PublicationSynergistic impact of magnesium compound as a potential dye additive for organic-based sensitizer in DSSCs(Elsevier, 2023)This study investigates the MgSO4 salt compound as the dye additive for dye treatment in dye-sensitized solar cells (DSSCs). The properties of the chlorophyll-based dye molecule sensitizer extracted from Mitragyna speciosa (MS) under the treatment of MgSO4 additive that contributed to the highest power conversion efficiency, PCE were examined. Field emission scanning electron micrograph, FESEM, X-ray diffraction, XRD, Fourier transform-IR, FTIR, UV-Vis spectroscopy, current to voltage characteristics, I-V and incidence photon to current efficiency, IPCE were used to investigate the structural, optical, chemical and also the electrical properties of the DSSC cells and their components. It was discovered that the extracted MS dye contained chlorophyll pigment, a powerful light-harvesting pigment required for the production of charge transfer and electricity. The MgSO4-treated dye provides stable pH conditions, faster electron injection due to higher band energy, Eg position, higher dye molecules adsorption, and reduced back recombination of electrons in the fabricated DSSC. As a result, all of the treated MgSO4 dye cell DSSCs outperformed the untreated dye cell, and at their optimal dye additive of 0.3 g (3-TM), the DSSC's current density, JSC, and associated PCE were higher at 2.08 mA/cm2 and 0.39%, respectively. Thus, using MS as a dye sensitizer in conjunction with an optimized MgSO4 compound as an additive resulted in improved photovoltaic effects, increased solar light absorption, and improved photon energy utilization.
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PublicationModeling of satellite-to-underwater integrated FSO-PON system using NOMA-VLC(MDPI, 2023)In recent years, optical wireless communication has promised several benefits over radio frequency communication in atmospheric, deep space and underwater communications. Satellite-to-underwater communication technology can be applied to commercial, naval, scientific and engineering operations because of its high data rate, high security, long-reach and low cost. In this paper, a high-speed, long-reach integrated free space optics (FSO)-passive optical network (PON) system using non-orthogonal multiple access visible light communication (NOMA-VLC) is proposed. It poses a 10/2.5 Gbps per channel bit rate for satellite-to-underwater applications. Numerically calculated results provide the splitter power budget of −35 dBm in the downlink and −32 dBm in the uplink. Additionally, a receiver sensitivity of 23 dB in the downlink and 10 dB in the uplink direction can be obtained in the system using a modified new zero cross-correlation (MNZCC) code under clear environment conditions. Again, the simulative analyses indicate that the suggested system supports 290 underwater devices successfully and offers a high 10 dBm signal-to-noise ratio over 10 km FSO, 100 km fiber and 5 m VLC range. Moreover, it provides a signal-to-noise ratio of 39 dB, with −9 dBm received optical power at 300 fields of view under fiber-wireless channels’ impairments. We argue that the suggested system is a symmetric system adapted to different link distances and which offers improved receiver sensitivity and high received optical power at a 10−9 bit error rate (BER). The comparative analysis shows the advantages of the suggested system over previously reported works.