Results 1 - 10 of 11
Results 1 - 10 of 11. Search took: 0.024 seconds
|Sort by: date | relevance|
[en] We have explored structural, electronic, optical and thermoelectric properties of cubic phase CH3NH3PbI3 hybrid organic-inorganic perovskite by the first principles calculation based on density functional theory. Density of States (DOS) and band structure calculations shows that CH3NH3PbI3 has direct band gap in R symmetry point (0.5 0.5 0.5) about 1.601 eV. A previous experimental and theoretical result agrees well with structural and electronic parameters. The optical properties such as dielectric constant, dispersion and absorption parameter have also been calculated. We have also performed thermoelectric properties like as Seeback coefficient, electrical conductivity, power factor, thermal conductivity and figure of merits at different temperature. The observed result shows that this material is optically active in the visible and ultraviolet regions, and therefore can be successfully used for optoelectronic devices. (paper)
[en] In this work, device modeling and simulation studies have been carried out with a variety of buffer layers over CIGS absorption layer. The band diagram, electric field variation and I/V curves are analyzed and device performance parameters i.e. efficiency, open circuit voltage, short circuit current, quantum efficiency are calculated. The efficiency of CIGS solar cell with ZnSe buffer layer is found comparable with that of CdS layer. The highest short circuit current is found for solar cell with ZnSe buffer layer, whereas the ZnS/CIGS heterojunction provides the highest quantum efficiency in the structures considered. The device physics is discussed and the effect of thickness of buffer layers and absorption layer is studied in order to find a more efficient and stable solar cell. (papers)
[en] Zinc chalcogenides (ZnX, X = S, Se and Te) have been increasing attention as wide and direct band gap semiconductor for blue and ultraviolet optical devices. This paper analyzes electronic and mechanical properties of these materials by ab initio pseudo-potential method that uses non conserving pseudopotentials in fully nonlocal form, as implemented in SIESTA code. In this approach the local density approximation (LDA) is used for the exchange-correlation (XC) potential. The calculations are given for band gap, elastic constants (C11, C12 and C44), shear modulus, and Young's modulus. The results are in very good agreement with previous theoretical calculations and available experimental data.
[en] Herein, we have measured the mobility of Hole’s for the configuration FTO/TiO2/CH3NH3PbBr3/PEDOT:PSS/Al by the SCLC regime. The current–voltage (I–V) characteristics of the CH3NH3PbBr3 perovskite based device shows the rectifying behavior as Schottky diode. Different parameters of the proposed device such as saturation current, ideality factor, barrier height have been taken out from I–V characteristics. The highest Hole’s mobility from TiO2 thin film through the perovskite and PEDOT:PSS film to the top aluminum electrode has of order 1.59 × 10–4 cm2 V–1 s–1. Moreover, the proposed device shows the TFSCLC regime at lower voltage while, at higher voltages it shows the TCLC regime. In addition to this, some important parameters like junction resistance, capacitance and carrier lifetime of device can be measured by the spectroscopy analysis of impedance.
[en] The present paper reports on the synthesis and characterization of methylammonium lead iodide perovskite thin film and its applications in heterojunction devices. Perovskite thin films were deposited by a simple spin-coating method using a precursor solution including methyl ammonium iodide and lead iodide onto a glass substrate. The surface morphology study via field emission scanning electron microscopy of the perovskite thin film shows complete surface coverage on glass substrate with negligible pin-holes. UV–visible spectroscopy study revealed a broad absorption range and the exhibition of a band-gap of 1.6 eV. The dark current-voltage (I–V) characteristics of all the devices under study show rectifying behaviour similar to the Schottky diode. Various device parameters such as ideality factor and barrier height are extracted from the I–V curve. At low voltages the devices exhibit Ohmic behaviour, trap free space charge limited conduction governs the charge transport at an intermediate voltage range, while at much higher voltages the devices show trap controlled space charge limited conduction. Furthermore, impedance spectroscopy measurements enable us to extract the various internal parameters of the devices. Correlations between these parameters and I–V characteristics are discussed. The different capacitive process arising in the devices was discussed using the capacitance versus frequency curve. (paper)
[en] Bauxite residue (BR) is the waste generated from alumina processing industries, which is considered as an environmental problem throughout world. Hence, utilization of BR is the need of the hour. In the present investigation, vacuum type bottom pouring mechanism is introduced in stir casting process to fabricate a low-cost particulate metal matrix composite (PMMC) using Al–Mg–Si alloy with BR as reinforcement. Controlled process parameters in terms of stirring speed and particle percentage were chosen in development of Al–Mg–Si/BR PMMC. The result of the microstructural study reveals uniform distribution of particles with 350 and 450 rpm of stirring speed. In this study, it was observed that increased BR weight fraction resulted in increased porosity content of the developed PMMC. Porosity content was found to have major impact on the microhardness of developed Al–Mg–Si/BR PMMC. The microhardness behavior of the developed PMMC was also predicted at different indentation loads. Microstructure was examined at both stirring speeds at different cross sections of the cylindrical samples. The reinforcement content was varied in a percentage range of 2–8% by weight. Beyond the limit of 8-wt% reinforcement concentration, defects like voids, local clustering, and agglomeration of particles were seen in the developed Al–Mg–Si/BR PMMC.
[en] In this paper the thermal variation of volume for NaCl, KCl, MgO and CaO has been investigated on the basis of Anderson model. We have evaluated the values of elastic constants C11, C44 and KT at different temperature on the basis of Murnaghan and Tallon models. Tallon's model with second approximation presents slightly better agreement with experimental results which shows that the Anderson-Grueneisen parameter is directly proportional to the volume ratio. Tallon's model can be used to evaluate the values of elastic constants for solids at different temperatures.
[en] Devices comprised of solution-processed poly (3-hexylthiophene) (P3HT)/multiwall carbon nanotubes (MWCNTs), with various concentrations of MWCNTs, were fabricated and characterized. The morphology of the P3HT: MWCNT nanocomposite was characterized by using field emission scanning electron microscopy (FESEM). The optical characteristics of the nanocomposite were studied by UV/VIS/NIR spectroscopy and Raman spectroscopy. The electrical properties of the fabricated devices were characterized by measuring the current density–voltage ( J – V ) characteristics. While the J – V characteristics of a pristine P3HT device reveal thermal injection limited charge transport, the P3HT: MWCNT nanocomposite-based devices exhibit three distinct voltage-dependent conduction regimes. The fitting curve with measured data reveals Ohmic conduction for a low voltage range, a trap-charge limited conduction (TCLC) process at an intermediate voltage range followed by a trap free space-charge limited conduction (SCLC) process at much higher voltages. A fundamental understanding of this work can assist in creating new charge transport pathways which will provide new avenues for the development of highly efficient polymer-based optoelectronic devices. (paper)
[en] Bismuth telluride (Bi2Te3) has myriad applications in the field of topological insulators and thermoelectrics. In the present work, Bi2Te3 nanostructures with two different morphologies were synthesized by wet chemical method. Prepared nanostructures were found to be polycrystalline with rhombohedral crystal structure and r3m space group. Formation of oxides along with Bi2Te3 was observed in the X-ray diffraction pattern and was further confirmed using Fourier transform infrared spectroscopy. Oxidation is an important parameter that affects the properties of the nanostructured materials. The morphological investigation done using transmission electron microscopy indicates the formation of nanoparticles and nanorod-like structures. Studies related to their thermal stability were performed using thermogravimetric analysis and differential scanning calorimetry. Thermal properties of nanostructures were further compared with bulk single crystals of Bi2Te3. Among the synthesized morphologies, nanoparticles showed highest thermal stability. Overall weight loss of nanoparticles was found to be 21% as compared to 55% for bulk Bi2Te3. High thermal stability of nanoparticles indicates that they may be more suitable as compared to their bulk counterparts for thermoelectric applications. (orig.)
[en] Economic growth is increasing the threat of climate change. It is triggering growth in global energy demand, which increased by 2.1% in 2017, (compared with 0.9% the previous year). This has made it difficult for countries to achieve the Paris 2015 Climate Accord objective to keep the global temperature rise below 2 degrees Celsius in 2050. It is now unclear how governments will be able to announce increased ambitions in line with the goal of holding global warming at 1.5 degrees Celsius in 2050. World Energy Markets Observatory (WEMO) is Capgemini's annual thought leadership and research report that includes useful insights and trends that every energy and utility player should know about as they plan for the future of their business. This 20. edition is drafted mainly from public data combined with Capgemini's expertise in the energy sector. Special expertise on regulation, climate challenges, and customer behavior has been provided by research teams at De Pardieu Brocas Maffei and VaasaETT. The current edition monitors the main indicators of the electricity and gas markets in Europe, North America, Australia, and South-east Asia and reports on developments and transformations in these sectors and addresses six main topics that include: Climate change and regulatory policies, Energy transition, Infrastructure and adequacy of supply, Supply and final customer, Transformation, Financials, Key Findings. Oil prices rose as high as US$80/barrel for the first time since 2014; this represents an increase of nearly 100% since January 2016. Global natural gas demand grew by 3%, thanks in large part to abundant and relatively low-cost supplies. China alone accounted for almost 30% of growth globally. Gas prices rose in Europe, Asia and North America in 2017, but remained below the 10-year average. Despite being the major commodity least loved by analysts, global coal demand rose about 1% in 2017, reversing the trend seen over the last two years. This growth was mainly due to demand in Asia, almost entirely driven by an increase in coal-fired electricity generation. Digital adoption has huge potential to decrease costs in the industry and service sector - among others, IoT and Blockchain witnessed progressive adoption. Grids are strongly impacted by the increased share of intermittent renewables and grid operators will strongly benefit from digitization. However, cyber security still remains a big concern, but this will not prevent utilities from deploying their digital transformation plans.