The electronic properties of ABX3 type compounds in the cubic phase are systematically studied using the first-principles calculations. The chemical trend of their properties as A or B or X varies is ...fully investigated. The optical properties of the ABX3 compounds are also investigated. Our calculations show that taking into account the spin–orbit coupling effect is crucial for predicting the accurate band gap of these halide perovskites. We predict that CH3NH3SnBr3 is a promising material for solar cells absorber with a perfect band gap and good optical absorption.
•Electronic and optical properties of ABX3 type compounds are investigated.•Chemical trend of their properties as A or B or X varies is presented.•Spin–orbit coupling effect is found to be crucial in this system.•CH3NH3SnBr3 is predicted to be a promising material for solar cells absorber.
To All Readers of IEEE Transactions on Consumer Electronics (TCE): I am pleased to announce that IEEE TCE will publish the first issue in 2024, i.e., Vol. 70, No. 1, as a special one to address the ...backlog of early access papers. This decision aligns with IEEE's publication policies, aiming to maintain the journal's commitment to timely scholarly communication.
This Communication describes polarity inversion in molecular rectification and the related mechanism. Using a supramolecular engineered, ultrastable, binary-mixed self-assembled monolayer (SAM) ...composed of an organic molecular diode (SC
BIPY) and an inert reinforcement molecule (SC
), we probed a rectification ratio (
)-voltage relationship over an unprecedentedly wide voltage range (up to |3.5 V|) with statistical significance. We observed positive polarity in rectification at |1.0 V| (
= 107), followed by disappearance of rectification at ∼|2.25 V|, and then eventual emergence of new rectification with the opposite polarity at ∼|3.5 V| (
= 0.006; 1/
= 162). The polarity inversion occurred with a span over 4 orders of magnitude in
. Low-temperature experiments, electronic structure analysis, and theoretical calculations revealed that the unusually wide voltage range permits access to molecular orbital energy levels that are inaccessible in the traditional narrow voltage regime, inducing the unprecedented
inversion of polarity.
This open access book provides practicing electrical engineers and students a practical – and mathematically sound – introduction to the topic of electromagnetic compatibility (EMC). The author ...enables readers to understand better how to overcome commonly failed EMC tests for radiated emission, radiated immunity, and electrostatic discharge (ESD), while providing concrete EMC design guidelines. The book also presents an overview of EMC standards and regulations and how to test for a global market access.
A synchronverter is an inverter that mimics synchronous generators, which offers a mechanism for power systems to control grid-connected renewable energy and facilitates smart grid integration. ...Similar to other grid-connected inverters, it needs a dedicated synchronization unit, e.g., a phase-locked loop (PLL), to provide the phase, frequency, and amplitude of the grid voltage as references. In this paper, a radical step is taken to improve the synchronverter as a self-synchronized synchronverter by removing the dedicated synchronization unit. It can automatically synchronize itself with the grid before connection and track the grid frequency after connection. This considerably improves the performance, reduces the complexity, and computational burden of the controller. All the functions of the original synchronverter, such as frequency and voltage regulation, real power, and reactive power control, are maintained. Both simulation and experimental results are presented to validate the control strategy. Experimental results have shown that the proposed control strategy can improve the performance of frequency tracking by more than 65%, the performance of real power control by 83%, and the performance of reactive power control by about 70%.
This paper investigates the capacitor-current-feedback active damping for the digitally controlled LCL-type grid-connected inverter. It turns out that proportional feedback of the capacitor current ...is equivalent to virtual impedance connected in parallel with the filter capacitor due to the computation and pulse width modulation (PWM) delays. The LCL-filter resonance frequency is changed by this virtual impedance. If the actual resonance frequency is higher than one-sixth of the sampling frequency (f s /6), where the virtual impedance contains a negative resistor component, a pair of open-loop unstable poles will be generated. As a result, the LCL-type grid-connected inverter becomes much easier to be unstable if the resonance frequency is moved closer to f s /6 due to the variation of grid impedance. To address this issue, this paper proposes a capacitor-current-feedback active damping with reduced computation delay, which is achieved by shifting the capacitor current sampling instant towards the PWM reference update instant. With this method, the virtual impedance exhibits more like a resistor in a wider frequency range, and the open-loop unstable poles are removed; thus, high robustness against the grid-impedance variation is acquired. Experimental results from a 6-kW prototype confirm the theoretical expectations.
Organohalide lead perovskites have revolutionized the scenario of emerging photovoltaic technologies. The prototype MAPbI3 perovskite (MA = CH3NH3 +) has dominated the field, despite only harvesting ...photons above 750 nm (∼1.6 eV). Intensive research efforts are being devoted to find new perovskites with red-shifted absorption onset, along with good charge transport properties. Recently, a new perovskite based on the formamidinium cation ((NH2)2CH+ = FA) has shown potentially superior properties in terms of band gap and charge transport compared to MAPbI3. The results have been interpreted in terms of the cation size, with the larger FA cation expectedly delivering reduced band-gaps in Pb-based perovskites. To provide a full understanding of the interplay among size, structure, and organic/inorganic interactions in determining the properties of APbI3 perovskites, in view of designing new materials and fully exploiting them for solar cells applications, we report a fully first-principles investigation on APbI3 perovskites with A = Cs+, MA, and FA. Our results evidence that the tetragonal-to-quasi cubic structural evolution observed when moving from MA to FA is due to the interplay of size effects and enhanced hydrogen bonding between the FA cations and the inorganic matrix altering the covalent/ionic character of Pb–I bonds. Most notably, the observed cation-induced structural variability promotes markedly different electronic and optical properties in the MAPbI3 and FAPbI3 perovskites, mediated by the different spin–orbit coupling, leading to improved charge transport and red-shifted absorption in FAPbI3 and in general in pseudocubic structures. Our theoretical model constitutes the basis for the rationale design of new and more efficient organohalide perovskites for solar cells applications.
In this paper, we propose the application of a dual material gate (DMG) in a tunnel field-effect transistor (TFET) to simultaneously optimize the on-current, the off-current, and the threshold ...voltage and also improve the average subthreshold slope, the nature of the output characteristics, and immunity against the drain-induced barrier lowering effects. We demonstrate that, if appropriate work functions are chosen for the gate materials on the source side and the drain side, the TFET shows a significantly improved performance. We apply the technique of DMG in a strained double-gate TFET with a high- k gate dielectric to show an overall improvement in the characteristics of the device, along with achieving a good on-current and an excellent average subthreshold slope. The results show that the DMG technique can be applied to TFETs with different channel materials, channel lengths, gate-oxide materials, gate-oxide thicknesses, and power supply levels to achieve significant gains in the overall device characteristics.
This work introduces the use of compressed sensing (CS) algorithms for data compression in wireless sensors to address the energy and telemetry bandwidth constraints common to wireless sensor nodes. ...Circuit models of both analog and digital implementations of the CS system are presented that enable analysis of the power/performance costs associated with the design space for any potential CS application, including analog-to-information converters (AIC). Results of the analysis show that a digital implementation is significantly more energy-efficient for the wireless sensor space where signals require high gain and medium to high resolutions. The resulting circuit architecture is implemented in a 90 nm CMOS process. Measured power results correlate well with the circuit models, and the test system demonstrates continuous, on-the-fly data processing, resulting in more than an order of magnitude compression for electroencephalography (EEG) signals while consuming only 1.9 μW at 0.6 V for sub-20 kS/s sampling rates. The design and measurement of the proposed architecture is presented in the context of medical sensors, however the tools and insights are generally applicable to any sparse data acquisition.
Resistive switching memory (RRAM) devices generally rely on the formation/dissolution of conductive filaments through insulating materials, such as metal oxides and chalcogenide glasses. ...Understanding the mechanisms for filament formation and disruption in resistive switching materials is a critical step toward the development of reliable and controllable RRAM for future-generation storage. In particular, the capability to control the filament resistance and the reset current through the compliance current during filament formation may provide a key signature to clarify the switching mechanism. This paper provides a physically based explanation for the universal resistance switching in bipolar RRAM devices. A numerical model of filament growth based on thermally activated ion migration accounts for the resistance switching characteristics. The same physical picture is extended to numerically model the reset transition. The impact of migration parameters and experimental setup on the set/reset characteristics is discussed through numerical simulations.
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