The Shift in Bandgap and Dielectric Constant Due to lattice Expansion in CH3NH3SnI3 Using FHI-aims

Although methyl ammonium lead iodide, (CH3NH3PbI3) has proven to be an effective photovoltaic material, there remains a main concern about the toxicity of lead, therefore determination of a lead free halide perovskite is of outstanding interest.  Sn2+ metal cations are the most obvious substitute for Pb2+ in the perovskite structure because of the similar s2 valence electronic configuration to Pb2+. Sn2+ can form a perovskite with a basic formula ASnX3 (A= CH3NH3 and X = halide) because the ionic radius of Sn2+ is similar to that of Pb2+. With the above similarity, methyl ammonium tin iodide CH3NH3SnI3 is one of the common replacement for CH3NH3PbI3 in the fabrication of organic-inorganic perovskite solar cells. FHI-aims code was used to perform the simulation of CH3NH3SnI3 in this work. Geometry building, parameter optimization, determination of the best exchange functional, k-grid convergence test along with determination of equilibrium lattice constant and geometry relaxation for CH3NH3SnI3 were carried out. An energy direct band gap of 1.051 eV was obtained, with an underestimation of 0.249 eV which amount to 19.2% when compared with experimental value. The lattice constant obtained using phonopy with ZPE is close to experimental reported values with an underestimation of 3.01%. The temperature dependent of lattice constant was studied in the temperature range of 0 to 318 K. At the same temperature range, shift in energy bandgap and dielectric constant due to lattice expansion was also investigated

First Principle Study on Lead-Free CH3NH3GeI3 and CH3NH3GeBr3 Perovskite solar cell using FHI-aims Code

An Ab-initio calculation in the framework of Density Functional Theory (DFT), as implemented in the FHI-aims package within Generalized Gradient Approximation (GGA) with the pbe parameterization was carried out in this work. Although methyl ammonium lead iodide (CH3NH3PbI3) has proven to be an effective photovoltaic material, there remains a main concern about the toxicity of lead.  An investigation into the possible replacement of CH3NH3PbI3 with CH3NH3GeI3 and CH3NH3GeBr3 as the active layer in perovskite solar cell was carried out. The electronic band structure, band gap energy and dielectric constants were calculated for CH3NH3GeI3 and CH3NH3GeBr3. The effect of temperature on linear thermal expansion coefficient and temperature dependence of lattice constant were studied in the temperature range of 273 to 318 K. Band gap shift due to lattice expansion was also studied. The dielectric constants of these materials were also determined. The energy band gap calculated for CH3NH3GeI3 and CH3NH3GeBr3 at their respective equilibrium lattice constant are 1.606 and 1.925eV respectively. A numerical simulation with some of these materials as the active layer in a perovskite solar cell was performed using General-purpose Photovoltaic Device Model (GPVDM) and the conversion efficiency of the resulting solar cell was obtained. Conversion efficiency of 10% and 8.4% were obtained for CH3NH3GeI3 and CH3NH3GeBr3 respectively

Photovoltaic conversion of laser energy

The Schottky barrier photovoltaic converter is suggested as an alternative to the p/n junction photovoltaic devices for the conversion of laser energy to electrical energy. The structure, current, output, and voltage output of the Schottky device are summarized. The more advanced concepts of the multilayer Schottky barrier cell and the AMOS solar cell are briefly considered

Visual Analytics to Support Atomistic Simulations Design

Nowadays, complex simulations of a variety of processes are extensively used in academia and industry. Particularly in academia, powerful scientific software tools are constantly developed to simulate complex systems; for instance, simulations of quantum transport using the non-equilibrium greens Function formalism. The potential impact of these scientific tools in industry is huge, but it is hindered by the lack of usability of the software by those who are not deeply familiar with it. Visual analytics is a new field that has shown the positive impact of interactive visualizations in software usability and the cognitive process of the user. This research investigates whether the implementation of interactive visual aids also improves the usability and the cognitive processes of research codes users, particularly those used for simulation design. To accomplish this goal, this study defines a framework for simulation design in scientific research, identifies the stages in which visual aids can be implemented to increase usability, and implements an interactive visualization system (NemoViz). NEMO5, a tool for designing atomistic simulation, is used as a case study to measure the effectiveness, efficiency, and user satisfaction of the use of visual aids in scientific simulation design. The results from this research provide a framework of reference for development of user-friendly simulation design tools, and will shed light on strategies that scientific developers might implement to broaden the impact of their simulation codes

Data availability and the need for research to localize, quantify and recycle critical metals in information technology, telecommunication and consumer equipment

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The supply of critical metals like gallium, germanium, indium and rare earths elements (REE) is of technological, economic and strategic relevance in the manufacturing of electrical and electronic equipment (EEE). Recycling is one of the key strategies to secure the long-term supply of these metals. The dissipation of the metals related to the low concentrations in the products and to the configuration of the life cycle (short use time, insufficient collection, treatment focusing on the recovery of other materials) creates challenges to achieve efficient recycling. This article assesses the available data and sets priorities for further research aimed at developing solutions to improve the recycling of seven critical metals or metal families (antimony, cobalt, gallium, germanium, indium, REE and tantalum). Twenty-six metal applications were identified for those six metals and the REE family. The criteria used for the assessment are (i) the metal criticality related to strategic and economic issues; (ii) the share of the worldwide mine or refinery production going to EEE manufacturing; (iii) rough estimates of the concentration and the content of the metals in the products; (iv) the accuracy of the data already available; and (v) the occurrence of the application in specific WEEE groups. Eight applications were classified as relevant for further research, including the use of antimony as a flame retardant, gallium and germanium in integrated circuits, rare earths in phosphors and permanent magnets, cobalt in batteries, tantalum capacitors and indium as an indium–tin-oxide transparent conductive layer in flat displays.BMBF, 033R087A, r³ - Strategische Metalle, Verbundvorhaben: UPGRADE - Integrierte Ansätze zur Rückgewinnung von Spurenmetallen und zur Verbesserung der Wertschöpfung aus Elektro- und Elektronikaltgeräten, TP1: Übergreifendes Stoffstrommanagement und Design für Recyclin

Fault isolation detection expert (FIDEX). Part 1: Expert system diagnostics for a 30/20 Gigahertz satellite transponder

LeRC has recently completed the design of a Ka-band satellite transponder system, as part of the Advanced Communication Technology Satellite (ACTS) System. To enhance the reliability of this satellite, NASA funded the University of Akron to explore the application of an expert system to provide the transponder with an autonomous diagnosis capability. The results of this research was the development of a prototype diagnosis expert system called FIDEX (fault-isolation and diagnosis expert). FIDEX is a frame-based expert system that was developed in the NEXPERT Object development environment by Neuron Data, Inc. It is a MicroSoft Windows version 3.0 application, and was designed to operate on an Intel i80386 based personal computer system

A BiCMOS current carrier transceiver on low voltage power lines

This paper presents a BiCMOS technology project of a Current Carrier Transceiver (CCT) for data and digital broadcasting on Low Voltage (LV) power lines (230-240~Vac). The CCT is the central piece in using the LV power lines network as communication channel for various "intelligent" sensors, actuators, monitors, and remote control for domotic or industrial purpose

A BiCMOS current carrier transceiver on low voltage power lines

This paper presents a BiCMOS technology project of a Current Carrier Transceiver (CCT) for data and digital broadcasting on Low Voltage (LV) power lines (230-240~Vac). The CCT is the central piece in using the LV power lines network as communication channel for various "intelligent" sensors, actuators, monitors, and remote control for domotic or industrial purpose