Single-Source Vapor-Deposited Cs2AgBiBr6 Thin Films for Lead-Free Perovskite Solar Cells

Lead-free double perovskites have been considered as a potential environmentally friendly photovoltaic material for substituting the hybrid lead halide perovskites due to their high stability and nontoxicity. Here, lead-free double perovskite Cs2AgBiBr6 films are initially fabricated by single-source evaporation deposition under high vacuum condition. X-ray diffraction and scanning electron microscopy characterization show that the high crystallinity, flat, and pinhole-free double perovskite Cs2AgBiBr6 films were obtained after post-annealing at 300 °C for 15 min. By changing the annealing temperature, annealing time, and film thickness, perovskite Cs2AgBiBr6 solar cells with planar heterojunction structure of FTO/TiO2/Cs2AgBiBr6/Spiro-OMeTAD/Ag achieve an encouraging power conversion efficiency of 0.70%. Our preliminary work opens a feasible approach for preparing high-quality double perovskite Cs2AgBiBr6 films wielding considerable potential for photovoltaic application.

BaTiO3 FILMS DEPOSITED ONTO TiNb AND Ti SUBSTRATES - AMOUNT AND STABILITY OF BARIUM

BaTiO₃ films deposited onto TiNb and Ti substrates using hydrothermal synthesis method were studied in the presented work. These films are supposed to improve properties of bone implants due to their ferroelectric behaviour, because ferroelectrics induce improved bone formation. A great question is the chemical stability of the used material. It can be crucial for its biocompatibility and possible in vivo application. We studied chemical composition of prepared samples, especially concentration of Ba and Ti and trends of these concentrations stimulated by a solution saline action. The Ba and Ti concentrations were determined by XPS under ultra - high vacuum condition. The BaTiO₃ films were investigated as received after the preparation procedure as well as after a long - time treatment in solution saline. Every sample was introduced to the solution saline at first for 1 and later for 3 weeks. Ti concentration almost does not change during our experiments while a meaningful Ba decrease is observed. Nevertheless, barium release seems to slow down with respect to the time of solution saline action. Stability of barium titanate films in a period of several months and an absolute amount of the released barium will be a subject of the next research.

Structure-property Characterisation at Nanoscale using In-situ TEM and SEM

<p>In-situ electron microscopy is an emerging technique for real time visualisation of micro-structural changes of a specimen under some applied constraints inside microscope. In this study, in-situ nanoindentation experimentation on a carbon nanocoil inside transmission electron microscope has been reported. The elastic modulus of the carbon nanocoil is found to be 177 GPa. Similar experiments are also carried out on carbon nanotubes, but force response of carbon nanotubes is beyond the limit of sensors presently available. The present study also reports the in-situ dissolution behavior of the secondary phases of a 7xxx series aluminum alloy under high vacuum condition in scanning electron microscope (SEM) in the temperature range of 350 °C to 400 °C. We report for the first time using in-situ SEM technique that dissolution of the MgZn2-base phase present as eutectic and divorced eutectic forms could start at a temperature as low as 300 °C, although the usual homogenisation temperature of such alloys is always &gt; 450 °C. Furthermore, the kinetics of dissolution of such phases, particularly when present in fine eutectic phase mixture, is significantly faster than what is observed under atmospheric pressure. It has been found that modification of surface composition under high vacuum condition plays a key role in the low temperature dissolution processes. It has further been found that the dissolution process does not start with the thinning of the IDC phase as proposed for Al-Zn-Mg-Cu alloys, rather it occurs by a combination of ‘spheroidisation’ and thinning process called ‘the thinning, discontinuation, and full dissolution’ (TDFD) mechanism. Results of the in-stu experiments under high vacuum are compared with the ex-situ dissolution experiments under normal atmospheric pressure.</p>

A new method for titania thin film production

In this research, transparent titania (TiO2) thin films were deposited on a glass microscope slide and on a flexible polyethylene terephthalate (PET) substrate under a high vacuum condition by means of the thermionic vacuum arc (TVA) method in a very short period of time (60 s). Optical properties and surface properties of the coated TiO2 surfaces are related to the structural changes of the coated layers due to ion energies and substrate effect. But obtained results are closely linked to literature values. Our analysis showed that the TVA method is an alternative method for low-temperature coatings and the produced films present important advantages for optical and industrial applications.

Effect of Varying Process Parameters on the Microstructure and Mechanical Properties of Cu-Cr-Zr-Ti Alloy Brazed Using Cu-Mn-Ni-Sn-Fe Foil

Cu-Cr-Zr-Ti alloy is being used widely in aerospace engines, due to its synergetic combination of high strength and thermal conductivity. Brazing is the preferred process being adopted to realize intricate shapes and complex dimensions. In the present work, Cu-Cr-Zr-Ti alloy was brazed using Cu-Mn-Ni-Sn-Fe base brazing foil. This braze foil exhibits liquidus temperature of ~980°C. Brazing experiments were carried out at 1030°C under high vacuum condition. The effect of varying load (0.5-2 kg) has been studied in the current experiment. Microstructural study of the parent materials and joints were carried out using optical microscope (OM). Lap shear testing (1T configuration) of the brazed joints was evaluated to obtain shear strength values. Also, micro-hardness traverse has been carried out across the brazed joint. Applied load plays a significant role in obtaining defect free braze joint.