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The power conversion efficiency of all-inorganic Sb 2 S 3 -on-Si two-terminal (2-T) monolithically integrated and four-terminal (4-T) mechanically stacked tandem solar cells are investigated. A one-dimensional solar cell capacitance simulator (SCAPS-1D) has been used to simulate the stand-alone antimony trisulfide (Sb 2 S 3 ) top sub-cell, silicon (Si) bottom sub-cell, 2-T monolithic, and 4-T mechanically stacked tandem solar cells. The stand-alone sub-cells are optimized by extensive studies, including interface defects density, bulk defects density, absorber layer thickness, and series resistance. The power conversion efficiency (PCE) of simulated stand-alone sub-cells is compared and verified with the existing literature. A current matching condition is established to characterize the 2-T monolithic Sb 2 S 3 -on-Si tandem cell. A filtered spectrum has been utilized for bottom sub-cell measurement in the tandem solar cells. The best-simulated PCE of Sb 2 S 3 -on-Si 2-T monolithic and 4-T tandem cells is 30.22% and 29.30%, respectively. The simulation results presented in this paper open an opportunity for the scientific community to consider Sb 2 S 3 as a potential top sub-cell material in Sb 2 S 3 -on-Si tandem solar cells with high PCE.

In this study, pristine MoS2 and MoS2/reduced graphene oxide (rGO) nanocomposites were synthesized using hydrothermal process. Different concentrations of graphene oxide (GO) precursor were used during the synthesis process. The electrochemical performance of the prepared composites was investigated in 1 M solution of H2SO4 on copper foil. The physico-chemical analysis affirms the systematic growth of MoS2 nanoflowers on rGO nanosheets. Furthermore, the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurement of MoS2 and MoS2/rGO nanocomposites were carried out. The CV and EIS measurements indicate that the charge transfer and specific capacitance (Csp) initially deteriorated slightly with low concentration of GO during synthesis, but with further increase in GO concentration, both parameters showed significant improvement compared to pristine MoS2. The MP demonstrated Csp of 193.50 Fg−1 at 5 mVs−1, whereas MG100 nanocomposite demonstrates higher Csp of 587.2 Fg−1 at same scan rate.

The Delhi Light source is a pre-bunched Free Electron Laser facility to generate coherent THz radiation. The electron beam is generated from a normal conducting 2.6 cell RF photocathode (PC) gun operated at 2860 MHz. The RF gun is powered by a high power RF source for a duration of 4 μs at 10 Hz repetition rate. The dark current during the operation of the RF gun has been found to be substantially high with increasing forward powers (above 3 MW) even after prolonged RF conditioning. Dark current measurements has been done with an in-house developed faraday cup with an objective to understand the possible primary dark current source from locations at the PC that witnesses high accelerating fields. The measurements include the study of solenoid field variation to understand the dark current energies and effect of its steering to understand the possible dark current locations. Simulations to make inference from the measurements has been done assuming different radial position of dark current emitters at the PC surface. The details of the measurements, simulation results and the inference drawn are discussed in the paper.

We successfully grew single crystals of Cs 2 AgFeCl 6 double perovskite measuring ~ 12 mm×01 mm using the acid precipitation method. The dielectric relaxation and charge conduction mechanism has been investigated using temperature-dependent impedance spectroscopy correlated with modulus spectroscopy. We observed the temperature-dependent transition relaxation mechanism from non-Debye-type to Debye-type and the negative temperature coefficient of resistance (NTCR)-type characteristics in Cs 2 AgFeCl 6 single crystals. Moreover, a significant change in dielectric properties, loss factor, electric modulus, and conductivity with temperature has been observed. This investigation provides essential insights into dielectric relaxation behaviour. It elucidates the carrier conduction mechanisms in Cs 2 AgFeCl 6 lead-free double perovskite single crystals that will help design a new optoelectronic device class.

The solid solution of multiferroic BiFeO 3 with antiferroelectric NaNbO 3 [i.e., Bi 1− x Na x Fe 1− x Nb x O 3 ] for x  = 0.20, 0.25, 0.30, 0.32, 0.38 and 0.40 prepared by means of high temperature solid state ceramic method are presented. X-ray diffraction analysis confirms the single-phase formation. Structural transformation in solid solution from rhombohedral to cubic phase has been observed with increasing NaNbO 3 concentration. The field emission scanning electron microscopy shows the formation of dense ceramic with a non-uniform grain size. Room temperature Raman studies also confirms a structural transformation in solid solution with increase in NaNbO 3 concentration. The structural transformation in solid solution has been explained on the basis of lattice strain induced by doping.

Microstructural and surface morphological studies of Co (2.5%) doped ZnS thin films deposited at different substrate temperatures ( T S ) of 200, 400 and 600 °C by means of pulsed laser deposition are presented. The deposited films are in wurtzite-hexagonal crystal structure as confirmed by X-ray diffraction and Raman spectroscopy techniques. The films deposited at higher T S show columnar morphology, as evidence by transmission electron microscopy measurements. Images of the surface topography have been taken by atomic force microscopy (AFM) for the film deposited at different T S . The film deposited at T S of 200 °C shows cone-like structures while deposited at T S of 400 and 600 °C show columnar structures. A fractal analysis has been performed on AFM images to understand the microstructure and surface morphology of thin film at different T S . Fractal analysis also reveals the morphological changes in the film with increasing T S . The observed ferromagnetism is correlated with columnar growth of the film which can be used as diluted magnetic semiconductor for spintronic applications.

The difference in the defect structures produced by different ion masses in a tungsten lattice is investigated using 80 MeV Au 7+ ions and 10 MeV B 3+ ions. The details of the defects produced by ions in recrystallized tungsten foil samples are studied using transmission electron microscopy. Dislocations of type b = 1/2[111] and [001] were observed in the analysis. While highly energetic gold ion produced small clusters of defects with very few dislocation lines, boron has produced large and sparse clusters with numerous dislocation lines. The difference in the defect structures could be due to the difference in separation between primary knock-on atoms produced by gold and boron ions.

Fabrications of ZnS nanocrystalline thin films at different substrate temperatures (T S ) of 200, 300 and 400 °C by means of pulsed laser deposition are presented. Thin film deposited at T S of 200 °C is in cubic zinc-blende (ZB) structure while those deposited at T S of 300 and 400 °C are in hexagonal wurtzite (W) phase. The grain size, surface roughness and bandgap of the films increases with increasing T S . The zinc vacancies and interstitials in the films increases while sulfur vacancies decreases with increasing T S . The variation of zinc and sulfur vacancies in ZnS films with T S is responsible for structural phase transition from ZB to W which causes the change in energy bandgap.

In this study, pristine MoS 2 and MoS 2 /reduced graphene oxide (rGO) nanocomposites were synthesized using hydrothermal process. Different concentrations of graphene oxide (GO) precursor were used during the synthesis process. The electrochemical performance of the prepared composites was investigated in 1 M solution of H 2 SO 4 on copper foil. The physico-chemical analysis affirms the systematic growth of MoS 2 nanoflowers on rGO nanosheets. Furthermore, the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurement of MoS 2 and MoS 2 /rGO nanocomposites were carried out. The CV and EIS measurements indicate that the charge transfer and specific capacitance ( C sp ) initially deteriorated slightly with low concentration of GO during synthesis, but with further increase in GO concentration, both parameters showed significant improvement compared to pristine MoS 2 . The MP demonstrated C sp of 193.50 Fg −1 at 5 mVs −1 , whereas MG100 nanocomposite demonstrates higher C sp of 587.2 Fg −1 at same scan rate.

We successfully grew single crystals of Cs2AgFeCl6 double perovskite measuring ~ 12 mm×01 mm using the acid precipitation method. The dielectric relaxation and charge conduction mechanism has been investigated using temperature-dependent impedance spectroscopy correlated with modulus spectroscopy. We observed the temperature-dependent transition relaxation mechanism from non-Debye-type to Debye-type and the negative temperature coefficient of resistance (NTCR)-type characteristics in Cs2AgFeCl6 single crystals. Moreover, a significant change in dielectric properties, loss factor, electric modulus, and conductivity with temperature has been observed. This investigation provides essential insights into dielectric relaxation behaviour. It elucidates the carrier conduction mechanisms in Cs 2 AgFeCl 6 lead-free double perovskite single crystals that will help design a new optoelectronic device class. KCI Citation Count: 0