Chemical synthesis and compositional analysis of mixed [Mo(S1 − x Se x )2] semiconductor thin films

The synthesis of binary MoS₂, MoSe₂ and mixed [Mo(S_{1 – x} Sex)₂] thin films onto a glass substrates using arrested precipitation technique (APT) is presented in this investigation. Growth kinetics and mechanism of film formation were studied for these films and are explained in brief. The stoichiometry of the film is confirmed by analyzing films using Extractive spectrophotometric (ESP), atomic absorption spectroscopic (AAS) and electron difftraction X-ray microanalysis (EDAX) techniques. The semiconductor solution containing Mo(VI) and Se(IV) is extracted with N-n-octylaniline in xylene and determined by ESP, AAS and EDAX techniques. Further these films are characterized for its semiconducting behavior to test the suitability of molybdenum chalcogenides as a photoelectrode to convert radiant energy into electricity. It is found that stoichiometry of the film formed by our recently developed arrested precipitation technique (APT) has strong influence on photoconduction in molybdenum chalcogenide photoelectrodes.     

A piezoelectric model based multi-objective optimization of robot gripper design

The field of robotics is evolving at a very high pace and with its increasing applicability in varied fields, the need to incorporate optimization analysis in robot system design is becoming more prominent. The present work deals with the optimization of the design of a 7-link gripper. As actuators play a crucial role in functioning of the gripper, the actuation system (piezoelectric (PZ), in this case) is also taken into consideration while performing the optimization study. A minimalistic model of PZ actuator, consisting different series and parallel assembly arrangements for both mechanical and electrical parts of the PZ actuators, is proposed. To include the effects of connector spring, the relationship of force with actuator displacement is replaced by the relation between force and the displacement of point of actuation at the physical system. The design optimization problem of the gripper is a non-linear, multi modal optimization problem, which was originally formulated by Osyczka (2002). In the original work, however, the actuator was a ‘constant output-force actuator model’ providing a constant output without describing the internal structure. Thus, the actuator model was not integrated in the optimization study. Four different cases of the PZ modelling have been solved using multi-objective evolutionary algorithm (MOEA). Relationship between force and actuator displacement is obtained using each set of non-dominated solutions. These relationships can provide a better insight to the end user to select the appropriate voltage and gripper design for specific application.     

Phosphorus- and silicon-containing amino curing agent for epoxy resin

Iranian Polymer Journal - Current research work focuses on the synthesis of phosphorus- and silicon-containing amine curing agent (PSA) for epoxy resins. PSA was synthesized using phenyl phosphonic...     

(Photo) electrochemical investigations on spray deposited n-CdIn 2Se4 thin film/polysulphide/c photoelectrochemical solar cell1

Cadmium indium selenide (n-CdIn ₂Se₄) thin films have been synthesized by spraying the mixture of an equimolar solutions of cadmium chloride [CdCl₂], indium trichloride [InCl₃] and selenourea [(NH₂)₂CSe] in aqueous media onto preheated fluorine doped tin oxide (FTO) coated glass substrates at optimized parameters of substrate temperature and solution concentration. The photoelectrochemical (PEC) cell configuration of n-CdIn₂Se/(l MNaOH + 1 MNa₂S + 1 M S)/C has been used for investigating the current—voltage (I–V) characteristics under dark and white light illumination, photovoltaic output, spectral response, photovoltaic rise and decay characteristics. The PEC study reveals the thin film of CdIn₂Se₄ exhibits n-type conductivity. The junction quality factor in dark (n _d) and light (n _l), series and shunt resistance (R _s and R _sh), fill factor (FF) and efficiency (η) for the cell have been estimated. The observed efficiency and FF of PEC solar cell is found to be 1.95 and 0.37% respectively. Mott-Schottky plot shows the flat-band potential (V _fb) of n-CdIn₂Se₄/(l M NaOH + 1 M Na₂S + 1 M S)/C cell to be—0.655 V/SCE.     

Studies on morphological and electrical properties of Al incorporated combusted iron oxide

The aluminium incorporated iron oxide samples were prepared by combustion route using aluminium nitrate and ferric trichloride as precursors. The samples were characterized for their morphological, dielectrical, impedance and thermal conductivity properties as a function of temperature. A strong low frequency dielectric dispersion is found to exist in these samples; this is ascribed to the presence of the ionized space charge carriers such as oxygen ion vacancies and interfacial polarization. The room temperature dielectric constant and the loss tangent (tan δ) at 1 kHz are 315 and 0.0855 for optimized 10 at.% Al:Fe₂O₃ sample, respectively. The frequency analysis of dielectric and ac conduction properties of these samples suggests the conduction process in these samples to be via oxygen ion vacancy motion through various defect sites. Impedance spectroscopy is used to characterize the electrical behavior. Results indicate that the relaxation mechanism of the material is temperature and frequency dependent and has dominant bulk contribution in different temperature ranges.     

Sensitized monomer fluorescence and excitation energy transfer in perylene-doped phenanthrene in crystalline and in polymer matrix

Sensitized monomer fluorescence and excitation energy transfer in crystalline and spin cast polymer films was investigated at room temperature. The fluorescence spectra of perylene doped phenanthrene reveals the characteristic monomeric emission of perylene and partial quenching of phenanthrene emission. The excimer formation of perylene is not observed in mixed crystalline luminophors and in spin cast films of the phenanthrene luminophors. The observed quenching of phenanthrene emission indicates the excitation energy transfer from phenanthrene to perylene in crystalline as well as in polymer matrix. Energy transfer is not observed in the experiments when phenanthrene and perylene were physically mixed where the components exist separately. The overlap between the excitation spectrum of perylene and emission spectrum of the phenanthrene supports the fact that the perylene molecules accept the excitation energy from phenanthrene. The energy transfer was found to depend upon the perylene concentration.     

Novel hybrid solar cells based on α-copper phthalocyanine–cadmium sulfide planar heterojunction

Cadmium sulfide (CdS) has been employed as an alternative acceptor for planar heterojunction solar cell based on copper phthalocyanine (CuPc). Spin-coated poly-3,4-ethylenedioxythiophene:polystyrenesulfonate (PEDOT:PSS) on indium tin oxide (ITO)-coated glass substrates was used for the vacuum deposition of CuPc and CdS planar heterojunction. In the present study, we have fabricated two different architectures of CuPc/CdS devices: (1) ITO/PEDOT:PSS/CuPc/CdS/Al and (2) ITO/PEDOT:PSS/CuPc/CdS/LiF/Al. Our results indicate that the CdS could effectively facilitate charge transport in the nanostructured network, and be a good acceptor. The fabricated bare CuPc/CdS device shows 0.13 % conversion efficiency while incorporation of LiF layer between CuPc/CdS and Al contact facilitates low-recombination rate results ~43 % enhancement in efficiency. The ITO/PEDOT:PSS/CuPc/CdS/LiF/Al device shows 0.30 % power conversion efficiency.