Findings and reports in the field of perovskite solar cells (PSCs) have been phenomenal and embrace diverse perspectives such as technical issues, yielding, marketing, and environmental concerns. Bottlenecks in the structure, manufacturing, and operation of PSCs have been frequently addressed; the use of various means including crystallography and kinetics studies, simulation, material, solution, and surface/interface engineering, as well as their outcomes, have yielded certified efficiency of 23.7%. However, the short lifecycle, large waste-to-harvest ratio, functional failure during bending and in the dark mode, environmental and stability issues, and lack of power storage hinder their commercial viability. As a remedy, PSCs can be teamed up with one or multiple mechanical or thermal energy-harvesting or electrochemical power storage devices that can fully or partially overcome these nonidealities. Here, the means of integrating different devices with PSCs to form hybrid packs are discussed. The factors contributing toward the efficiency and mechanical robustness of PSCs and their hybrid devices upon integration are investigated. As an essential bridging component, carbon electrodes are also considered. Furthermore, due to the pressing standards in the energy sector, hybrid devices with nontoxic lead (Pb)-free perovskites should form ideal power packs. Therefore, with reference to their lattice model, optical characteristics, and resulting photovoltaic (PV) performance, they have also been briefly highlighted.

Perovskite solar cell-hybrid devices: thermoelectrically, electrochemically, and piezoelectrically connected power packs

This paper presents a comprehensive TCAD based assessment to evaluate the intrinsic gain and minimum noise figure metrics of the T – Gate, and the π – Gate AlGaN/AlN/GaN HEMTs along with their recessed architectures. The work presented in this paper, to the best of author’s knowledge, is first in its attempt to systematically bring out both the effect of minimum noise figure metrics and intrinsic gain at the device level for the π – Gate architecture and their recessed counterparts whilst evaluating its stability for high frequency operations. Comparison demonstrates an enhancement in intrinsic gain by 64.5% in case of asymmetric π – Gate and 77% for asymmetric recessed π – Gate in comparison to their T – Gate counterparts. Further, the said architectures possess a wider range of flat gain operation with suppressed values of minimum noise figure metrics. These modifications result in a modest trade off in the minimum noise figures when best case is considered and compared with their T – Gate counterparts. Additionally, it is also demonstrated that such device architectures demonstrate much stable high frequency operation in comparison to their primer. The results so presented establish the superiority of the π – Gate AlGaN/AlN/GaN HEMTs for low noise and high gain applications.

Optimization of π – Gate AlGaN/AlN/GaN HEMTs for Low Noise and High Gain Applications

Gallium nitride (GaN)-based high-electron mobility transistors (HEMTs) are widely used in high power and high frequency application fields, due to the outstanding physical and chemical properties of the GaN material. However, GaN HEMTs suffer from degradations and even failures during practical applications, making physical analyses of post-failure devices extremely significant for reliability improvements and further device optimizations. In this paper, common physical characterization techniques for post failure analyses are introduced, several failure mechanisms and corresponding failure phenomena are reviewed and summarized, and finally device optimization methods are discussed.

Recent progress of physical failure analysis of GaN HEMTs

Modelling of InAs nanowire and MOSFET under phonon emission and absorption by using NEGF formalism

Nowadays, the increasing intention in the research community on small sized electrical energy generators due to the wide use of wireless sensor networks and the drawbacks of conventional chemical batteries, such as their limited lifespan and large physical dimensions. Therefore, the principle of harvesting energy from solar power, electromagnetic fields, wind and the human body have been introduced as alternatives. Among these energy resources, wind energy is clean, renewable and can be easily turned into mechanical vibrations that can be used to generate electrical energy via vibration-to-electrical energy conversion mechanisms using electromagnetic, electrostatic and piezoelectric transducers. From these transducers, piezoelectric materials have received the most attention because of their higher conversion efficiency. Therefore, flexible piezoelectric cantilever was tested for characterized cantilever in vibration energy harvesting. The parameters of the cantilever such as length, width and thickness were varied and investigated for energy conversion and performance. The piezoelectric cantilever was designed and simulated using COMSOL Multiphysics 5.5 tool. The simulation result and performance of each design was compared. Performances were plot based on generated voltage vs applied vibration frequency. Result shows that generated voltage of 4.3V at applied vibration frequency of 155Hz was the most optimal result compared to the rest of the design for a piezoelectric cantilever with the width, length and height of 30mm, 20mm and 0.2mm respectively. This was ideal as most of the devices nowadays uses 5V supply and the small design allows the piezoelectric cantilever to be portable or even easily installed in projects that utilizes it.

Sanam Kala

Papers

Nanocrack formation due to inverse piezoelectric effect in AlGaN/GaN HEMT