Physics

In optical imaging, the resolution of the imaging system is not only limited by the aperture and imperfection of the lens, but also by the CCD nonzero pixel size and separation between the two consecutive pixels. We deal only with the geometric superresolution and assume that the size of the CCD pixels is much smaller in comparison with the separation between the pixels. The separation between the pixels limits the resolution of the CCD camera. Our object is to address this problem. In the proposal, we focus on exceeding the geometric resolution with a new approach in which no moving element of the imaging system is used, but only a mask is placed at the Fourier transform plane. This mask encodes the input data. The encoded image is captured by the CCD. The captured image is then Fourier transformed and a decoding mask is used to nullify the effect of undersampling by the CCD. Mathematical modeling and simulation in one dimension are presented.

In optical imaging, the resolution of the imaging system is not only limited by the aperture and imperfection of the lens, but also by the CCD nonzero pixel size and separation between the two consecutive pixels. We deal only with the geometric superresolution and assume that the size of the CCD pixels is much smaller in comparison with the separation between the pixels. The separation between the pixels limits the resolution of the CCD camera. Our object is to address this problem. In the proposal, we focus on exceeding the geometric resolution with a new approach in which no moving element of the imaging system is used, but only a mask is placed at the Fourier transform plane. This mask encodes the input data. The encoded image is captured by the CCD. The captured image is then Fourier transformed and a decoding mask is used to nullify the effect of undersampling by the CCD. Mathematical modeling and simulation in one dimension are presented.

The technology of liquid crystal panels (LCP) is very mature and can be applied in many different areas in which the
modulation of an input light beam is needed. LCP can be used to modulate amplitude, phase or polarization state of the
input beam, being the phase modulation the most important. For this reason parallel aligned LCP are the most
recommended for most applications. In this paper we review a method for the characterization of these devices,
especially when temporal fluctuations are present. Next we revise several applications in different fields: a) A point
diffraction interferometer with phase shifting capabilities isdemonstrated and applied to the recording of digital
holograms that can focus, digitally, the different planes of a 3D object; b) Different techniques to obtain superresolution
imaging beyond the diffraction limit of the aperture, or the geometrical limitation imposed by the pixilation of the CCD
device are shown, and c) the construction of Stokes and Mueller polarimeters with different types of LCP are also
shown.

The resolution of any imaging system is limited by many factors, as by the diffraction resolution limit
of the system or by resolution limitations related to the geometry of the optical elements. One of the
main geometrical limitations in optical systems is due to CCD cameras used for the image acquisition.
In  particular,  pixel  size,  shape  and  pixel  pitch  of  the  used  CCD  camera  always  impose  a  limit  in
resolution. This paper faces the problem of the geometric super-resolution limitation, providing an
approach  free  of  mechanical  movements,  which  helps  to  overcome  the  problems  related  to  CCD
pixels pitch. To this aim, a parallel aligned (PA) liquid crystal on silicon (LCoS) display is placed at the
Fourier plane of a transparent object, and different linear phases are addressed to it. Afterwards, an
image-forming  optical  system  provides  the  final  image  of  the  object  at  the  CCD  camera  plane.  By
addressing  different  linear  phases  to  the  LCoS  display,  object  images  with  different  sub-pixel
displacements  in  1-D  are  acquired  by  the  CCD  camera.  Afterwards,  all  the  shifted  images  are
combined,  leading  to  a  final  super-resolved  image  with  larger  dimension  than  the  original  object
image. In addition, an inverse filtering process is also included into the proposed method,  leading to
certain extent, to a decrease of the blurring effect. The experimental comparison of the object images
obtained  with  and  without  using  the  proposed  technique  provides  the  improvement,  in  terms  of
resolution, achieved by applying our technique.

A molecular model of the human A 2B adenosine receptor containing seven transmembrane R helices connected by three intracellular and three extracellular hydrophilic loops had been constructed. A molecular docking of seven structurally diverse xanthine antagonists of the A 2B receptor was performed, and the differences in their binding modes were investigated. The 1 ns molecular dynamics (MD) simulations of several obtained ligand-receptor complexes inserted into the phospholipid bilayer were carried out. The conformational changes of the A 2B receptor occurring during MD simulations were explored, and the stable binding modes of the studied antagonists were determined. According to the models presented in this work, the involvement of the His251, Asn282, Ser92, Thr89, and some aromatic residues in ligand recognition was determined. The obtained binding modes of the A 2B antagonists demonstrate good agreement with the site-directed mutagenesis data. Figure 2. Binding modes of the A2B receptor antagonists.

The Ag/PTCDA/PEDOT:PSS/p-Si Schottky diode has been fabricated by adding a layer of organic
compound 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) on top of the p-Si for which the
junction characteristics have been investigated. The electronic properties of the device have been
studied by the conventional I–Vand the Norde’s methods. For conventionalI–Vmeasurements the
rectifying behavior has been observed with a rectification ratio of 236. The barrier height and ideality
factor values of 0.81 eV and 3.5, respectively, for the structure have been obtained from the forward
bias I–V characteristics. Various electrical parameters such as reverse saturation current, series
resistance and shunt resistance have been calculated from the analysis of experimental I–Vresults
and discussed in detail. The barrier height and the series resistance determined by the Norde’s function
are found in good agreement with the values calculated from conventionalI–Vmeasurements. The
charge conduction mechanism has also been discussed.

Three 3,6-di(4-methoxyphenyl)amino N-alkylated carbazoles were synthesized, characterizeda nd incorporated in solid state dye-sensitized solar cells. Devices using these compoundsa ss olid hole conductors showedr elative high V oc thanks to good energy level matching betweent hem and D102 dye. However,t hey yield relativelyl ow J sc and FF compared to spiro-OMeTAD-based control devices, which is due to an order of magnitude lower mobility and conductivity with respect to spiro-OMeTAD. Maximum PCEs for Nethyl and N-hexyl 3,6-di(4-methoxyphenyl)amino carbazoles (2a, 2b) are 1.6 %, and 1.8 %r espectively,w hereas spiro-OMeTAD devices gave 4.4 %. Stability tests in air under continuousillumination have been reported.

Electro-spray deposition (ESD) was applied to fabricate solution processed donor-acceptor bulk heterojunction organic photovoltaic devices with multi-layer structure. Solvent effect was observed when using different organic solvents. Power conversion efficiency (PCE) of the devices prepared from dichlorobenzene increased dramatically comparing to the ones from chloroform, owing to improved homogeneity of the films. ESD enabled us to fabricate solution processed multi-layer (donor/donor:acceptor/acceptor) devices with simple successive deposition steps. Energy Dispersive X-ray Reflectometry analysis confirmed distinct three layered structure of the active layers. Solar cell device parameters of the trilayer devices were compared to single layer devices and those of spin coated devices with the same donor:acceptor ratio and film thickness. Post-thermal treatment results showed that after annealing at 125°C, trilayer devices exhibited best performance with the maximum PCE of 2.17%.

A detailed investigation of the optimal set of parameters employed in multilayer device fabrication obtained through successive electrospray deposited layers is reported. In this scheme, the donor/acceptor (D/A) bulk heterojunction layer is sandwiched between two thin stacked layers of individual donor and acceptor materials. The stacked layers geometry with optimal thicknesses plays a decisive role in improving operation characteristics. Among the parameters of the multilayer organic photovoltaics device, the D/A concentration ratio, blend thickness and stacking layers thicknesses are optimized. Other parameters, such as thermal annealing and the role of top metal contacts, are also discussed. Internal photon to current efficiency is found to attain a strong response in the 500 nm optical region for the most efficient device architectures. Such an observation indicates a clear interplay between photon harvesting of active layers and transport by ancillary stacking layers, opening up the possibility to engineer both the material fine structure and the device architecture to obtain the best photovoltaic response from a complex organic heterostructure.

We used the electrospray deposition (ESD) method to fabricate organic photovoltaic devices with poly (3-hexyl-thiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) blends of different composition ratios and different organic solvent solution, namely chloroform (CLF) and dichlorobenzene (DCB). The morphology and crystallinity of the active layers were investigated by means of atomic force microscopy (AFM), two-dimensional X-ray diffraction (XRD 2 ) and optical absorption, spreading light on the peculiarities of the present growth technique, involving much faster solvent evaporation and film forming processes, and comparatively much more ordered strutures with less need of thermal annealing processes. The power conversion efficiency (PCE) under AM 1.5G solar simulation obtained for devices deposited from DCB as compared to those deposited from CLF, showed significant improvement, in fair agreement with what was found by the overall characterization of the physical properties.

In this article, we study the phase-field model of solidification for numerical simulation of dendritic crystal growth that occurs during the casting of metals and alloys. Phase-field model of solidification describes the physics of dendritic growth in any material during the process of under cooling. The numerical procedure in this work is based on finite difference scheme for space and the 4th-order Runge-Kutta method for time discretization. The effect of each physical parameter on the shape and growth of dendritic crystal is studied and visualized in detail.

The physicochemical properties of eumelanin thin films realized by spray and electrospray deposition methods were investigated. We find a consistent improvement above the film quality reached from liquid solution, minimizing the detrimental effect of the solvent in the final morphology of the films. Furthermore a clear trend towards specific aggregation modalities made us able to significantly unveil some of the cumbersome physical mechanisms at the basis of the various properties that are often invoked for this important functional biomaterial. In particular, temperature dependent electrical resistance evidenced a semiconductor-like character, with peculiar features of melanin organization explicated through crosslinked secondary structure as emerged from many observations obtained by different spectroscopic and microscopic techniques. and is currently working on graphene, organic/inorganic semiconductors and their composites for energy-related applications. University Mardan,

Organic solar cells, processed from solution at various optimizing device parameters, were investigated. The device's active-layer film-thicknesses were optimized while depositing at different spin speeds where 120-nm-thick layer (D2) gives maximum power conversion efficiency of 2.9%, annealed at 165 °C. The reason is ascribed as sufficient light absorption, excitons dissociation/diffusion and carriers transportation. In the case of Ca/Al, being as a top electrode rather than LiF/Al and Al, substantial efficiency enhancement, from 1.70% to 2.78%, was obtained at low temperature, 130 °C, providing ease for charge collection and pertaining conductive nature of increased resistivity at high temperature.

The photoconversion efficiency of dye sensitized solar cells can be enhanced by the incorporation of light management nanostructures such as photonic crystals. Here, we present a facile route to incorporate titania inverse opals into solid state dye sensitized solar cells and report photoconversion efficiency enhancements of up to 56% compared with a model system without the inverse opal. Our approach is based on the precise design of titania inverse opals with a predetermined thickness that can be controlled at the individual layer level. By choosing an inverse opal exhibiting a photonic bandgap which overlaps the absorption bands of the dye, our results show that there is an optimal thickness of the inverse opal structure for maximum efficiency enhancement of the cell. This is the first experimental proof that the thickness of a titania inverse opal plays a pivotal role in cell efficiency enhancement in solid state dye sensitized solar cells.

Inverted organic solar cells by bulk-heterojunctions were fabricated using TiO 2 and ZnO as electron extraction layers. Electrospray deposition was applied to fabricate trilayer structures with thin donor and acceptor layers sandwiching bulk-heterojunction layers. Comparing to single layer devices, trilayer devices show significantly enhanced stability in device performances under continuous illumination in air. Conventional structure devices with Al as electron extraction layer were also compared showing how the improvement achieved with the inverted architecture is surprisingly higher. Our results, on a basis of 4 h of continuous operations, show how combining inverted device architecture with trilayer configuration is a viable approach in achieving highly stable organic solar cells with 70% retainment of the initial PCE to be compared to the 13% in the case of direct trilayer BHJ.

Structural and electronic properties of homogeneous poly(3-Hexylthiophene) (P3HT) films obtained from the electro-spray method were presented by means of grazing incidence x-ray diffraction, atomic force microscopy, optical absorption, photoelectron spectroscopy and (photo)electrical conductivity. Different structural conformations were obtained starting from different solution concentrations and flow rate conditions. The electro-spray method was shown to effectively expand the control of the conformation and assembling of the polymers films, opening the way to the possibility of tailoring film characteristics according to device specifications.

Electro-spray deposition (ESD) was applied to fabricate solution processed donor-acceptor bulk heterojunction organic photovoltaic devices with multi-layer structure. Solvent effect was observed when using different organic solvents. Power conversion efficiency (PCE) of the devices prepared from dichlorobenzene increased dramatically comparing to the ones from chloroform, owing to improved homogeneity of the films. ESD enabled us to fabricate solution processed multi-layer (donor/donor:acceptor/acceptor) devices with simple successive deposition steps. Energy Dispersive X-ray Reflectometry analysis confirmed distinct three layered structure of the active layers. Solar cell device parameters of the trilayer devices were compared to single layer devices and those of spin coated devices with the same donor:acceptor ratio and film thickness. Post-thermal treatment results showed that after annealing at 125°C, trilayer devices exhibited best performance with the maximum PCE of 2.17%.