Kodakkal Kannan Viswanathan

Abstract: We have presented a detailed analysis of the phase transition kinetics and binding energy states of solution processed methylammonium lead iodide (MAPbI3) thin films prepared at ambient conditions and annealed at different elevated temperatures. It is the processing temperature and environmental conditions that predominantly control the crystal structure and surface morphology of MAPbI3 thin films. The structural transformation from tetragonal to cubic occurs at 60 °C with a 30 minute annealing time while the 10 minute annealed films posses a tetragonal crystal structure. The transformed phase is greatly intact even at the higher annealing temperature of 150 °C and after a time of 2 hours. The charge transfer interaction between the Pb 4f and I 3d oxidation states is quantified using XPS.

Abstract: Knit-coir-mat-like structured CuS thin films prepared by chemical bath deposition with different time duration were used as counter electrode in qunatum dot sensitized solar cells. The film deposited at 4 h exhibited better electrochemical and photovoltaic performance with JSC, VOC, and FF values of 14.584 mA cm–2, 0.566 V, and 54.57% and efficiency of 4.53%. From the UV–vis absorption spectra, it is observed that CuS thin film exhibits free carrier intraband absorption in the longer wavelengh region. The enhanced performance of CuS counter electrodes is due to Cu vacancies with increased S composition, and the quasi-Fermi energy level in semiconductors with respect to electrolyte redox potential is one of the causes that affects the electrocatalytic activity of counter electrodes.

Abstract: A facile chemical bath deposited (CBD) CuS nanoflakes and nano platelets are used as an effective counter electrode (CE) for quantum dot sensitized solar cells (QDSSC) and the effect of seed layer assistance has been discussed. The CuS thin films used as CE exhibit intraband transitions in the longer wavelength region with direct band gap and the surface exhibits unique morphology depending upon the seed layer. The photovoltaic performance of TiO2/CdS/CdSe/ZnS cascade QDSSC with CuS as CE prepared at 60 °C shows increased electrocatalytic activity in polysulfide electrolyte with higher short- circuit current density, open circuit voltage, fill factor and a conversion efficiency of 4.02%.

Abstract: The energy dependence of efficiency and resolution of HPGe and NaI(Tl) detectors using gamma-ray spectroscopy were investigated in this paper. It was found that the resolution of the detector was directly proportional to the energy of gamma-ray and its efficiency was exponentially proportional to the gamma-ray energy. The resolution of HPGe detector (GC2018, diameter 60.5 mm and length 31.5 mm) is better than NaI(Tl) detector (ORTEC 905-3, size 2’’ × 2’’) and efficiency of NaI(Tl) is larger than HPGe detector. Key words: HPGe, NaI(Tl), gamma ray, resolution, efficiency.

Abstract: Spline function approximation technique is used to analyze the free vibration of symmetric and anti-symmetric cross-ply plates under shear deformation theory. The equations of motion of the plate are derived using YNS theory. A system of coupled differential equations in terms of displacement and rotational functions are obtained by assuming the solution in a separable form. These functions are approximated using Bickley-type splines of suitable orders. A generalized eigenvalue problem is obtained on applying the process of point collocation with suitable boundary conditions. Parametric studies have been made to investigate the frequency response of the plates with reference to the material properties, number of layers, fiber orientation, side-to-thickness ratio, aspect ratio and relative layer thickness. Some results are compared with existing solution obtained by FEM.

Abstract: Adopted values for the reduced electric quadrupole transition probability, B(E2)↑, from the ground state to the first-excited 2+ state of even–even nuclides are given in Table I. Values of τ, the mean life of the 2+ state; E, the energy; and β, the quadrupole deformation parameter, are also listed there. The ratio of β to the value expected from the single-particle model is presented. The intrinsic quadrupole moment, Q0, is deduced from the B(E2)↑ value. The product E×B(E2)↑ is expressed as a percentage of the energy-weighted total and isoscalar E2 sum-rule strengths. Table II presents the data on which Table I is based, namely the experimental results for B(E2)↑ values with quoted uncertainties. Information is also given on the quantity measured and the method used. The literature has been covered to November 2000. The adopted B(E2)↑ values are compared in Table III with the values given by systematics and by various theoretical models. Predictions of unmeasured B(E2)↑ values are also given in Table III.

Abstract: This review captures the synthesis, assembly, properties, and applications of copper chalcogenide NCs, which have achieved significant research interest in the last decade due to their compositional and structural versatility. The outstanding functional properties of these materials stems from the relationship between their band structure and defect concentration, including charge carrier concentration and electronic conductivity character, which consequently affects their optoelectronic, optical, and plasmonic properties. This, combined with several metastable crystal phases and stoichiometries and the low energy of formation of defects, makes the reproducible synthesis of these materials, with tunable parameters, remarkable. Further to this, the review captures the progress of the hierarchical assembly of these NCs, which bridges the link between their discrete and collective properties. Their ubiquitous application set has cross-cut energy conversion (photovoltaics, photocatalysis, thermoelectrics), en...

Abstract: Perovskite solar cells have shown unprecedent performance increase up to 22% efficiency. However, their photovoltaic performance has shown fast deterioration under light illumination in the presence of humid air even with encapulation. The stability of perovskite materials has been unsolved and its mechanism has been elusive. Here we uncover a mechanism for irreversible degradation of perovskite materials in which trapped charges, regardless of the polarity, play a decisive role. An experimental setup using different polarity ions revealed that the moisture-induced irreversible dissociation of perovskite materials is triggered by charges trapped along grain boundaries. We also identified the synergetic effect of oxygen on the process of moisture-induced degradation. The deprotonation of organic cations by trapped charge-induced local electric field would be attributed to the initiation of irreversible decomposition.

Abstract: Thank you for reading physical and computational aspects of convective heat transfer. Maybe you have knowledge that, people have search hundreds times for their chosen readings like this physical and computational aspects of convective heat transfer, but end up in malicious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they are facing with some harmful virus inside their computer.

Abstract: Quantum dot-sensitized solar cells (QDSCs) have emerged as a promising candidate for next-generation solar cells due to the distinct optoelectronic features of quantum dot (QD) light-harvesting materials, such as high light, thermal, and moisture stability, facilely tunable absorption range, high absorption coefficient, multiple exciton generation possibility, and solution processability as well as their facile fabrication and low-cost availability. In recent years, we have witnessed a dramatic boost in the power conversion efficiency (PCE) of QDSCs from 5% to nearly 13%, which is comparable to other kinds of emerging solar cells. Both the exploration of new QD light-harvesting materials and interface engineering have contributed to this fantastically fast improvement. The outstanding development trend of QDSCs indicates their great potential as a promising candidate for next-generation photovoltaic cells. In this review article, we present a comprehensive overview of the development of QDSCs, including: (1) the fundamental principles, (2) a history of the brief evolution of QDSCs, (3) the key materials in QDSCs, (4) recombination control, and (5) stability issues. Finally, some directions that can further promote the development of QDSCs in the future are proposed to help readers grasp the challenges and opportunities for obtaining high-efficiency QDSCs.