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[IEEE 2018 IEEE International Electron Devices Meeting (IEDM) - San Francisco, CA, USA (2018.12.1-2018.12.5)] 2018 IEEE International Electron Devices Meeting (IEDM) - Demonstration of High-speed Hysteresis-free Negative Capacitance in Ferroelectric Hf<inf>0.5</inf>Zr<inf>0.5</inf>O<inf>2</inf>
摘要： We report the experimental observation of hysteresis-free negative capacitance (NC) in thin ferroelectric Hf0.5Zr0.5O2 (HZO) films through high-speed pulsed charge-voltage measurements. Hysteretic switching is suppressed by the addition of thin Al2O3 layers on top of the HZO to prevent the screening of the polarization. We observe an S-shaped polarization-electric field dependence without hysteresis in agreement with Landau theory, which enables direct extraction of NC modeling parameters for ferroelectric HZO. Hysteresis-free NC is demonstrated down to 100 ns pulse widths limited only by our measurement setup. These results give critical insights into the physics of ferroelectric NC and practical NC device design using ferroelectric HZO.
关键词： hysteresis-free,Hf0.5Zr0.5O2,ferroelectric,negative capacitance,pulsed measurements,Landau theory
更新于2025-09-19 17:15:36
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Halide perovskites for resistive random-access memories
摘要： Halide perovskite based resistive random-access memory (ReRAM) devices are emerging as a new class of revolutionary data storage devices because their switching material—halide perovskite—has received considerable attention in recent years. Among the electrical characteristics of the material, its current–voltage (I–V) hysteresis, which may occur due to defect formation and migration, means that ReRAM can employ halide perovskites as a resistive switching material. Many studies have been conducted on resistive switching materials; however, the investigation of halide perovskites for ReRAM devices is still in the early research stages; therefore, the application of halide perovskites in ReRAM devices is a topic worth studying. Herein, we introduce halide perovskites and their operating mechanism within a ReRAM device. Moreover, recent notable achievements along with future challenges have been reviewed.
关键词： Halide perovskites,ion migration,hysteresis,resistive random-access memories,switching materials,ReRAM
更新于2025-09-19 17:15:36
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Fixed frequency integral sliding-mode current-controlled MPPT boost converter for two-stage PV generation system
摘要： In two-stage grid-integrated photovoltaic (PV) system, usually a DC–DC converter is employed between the PV modules and the inverter. The dynamic interactions between the DC–DC converter, inverter, and the maximum power point tracking (MPPT) controller may affect the system performances. This study gives an integral procedure to design a stable sliding-mode controller (SMC) based on fixed frequency equivalent control approach to improve the transient response of PV system and to track the reference voltage supplied by the voltage-oriented MPPT controller in the presence of environmental and load perturbations and converter output sinusoidal perturbations imposed by the second harmonic of the grid frequency. The controller consists of fast current tracking inner current loop based on SMC law whose sliding surface is defined by the input capacitor and inductor current and outer PI controller maintains required PV voltage regulation. The superiority of the controller is validated at different operating conditions through PSIM software and its performance is compared with variable frequency hysteresis-based SMC. To check the static and transient performances of the system, various experiments are conducted. The results obtained show very fast transient response in settling time and alleviation of chattering magnitude at various operating conditions.
关键词： maximum power point tracking (MPPT),DC–DC converter,transient response,PSIM software,settling time,chattering magnitude,voltage regulation,photovoltaic (PV) system,fixed frequency,sliding-mode controller (SMC),hysteresis-based SMC
更新于2025-09-19 17:13:59
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Wideband Hybrid Envelope Tracking Modulator With Hysteretic-Controlled Three-Level Switching Converter and Slew-Rate Enhanced Linear Amplifier
摘要： A wideband hybrid Envelope tracking (ET) modulator utilizing a hysteretic-controlled three-level switching converter (3L-SWC) and a slew-rate enhanced linear ampli?er (LA) are presented. In addition to smaller ripple and lower losses of 3L-SWCs, employing the proposed hysteresis control results in a higher speed loop and wider bandwidth converter, enabling over 80 MHz of switching frequency. A concurrent sensor circuit monitors and regulates the ?ying capacitor voltage VCF and eliminates the conventionally required calibration loop to control it. The hysteretic-controlled 3L-SWC provides a high percentage of power ampli?er (PA) supply load current with lower ripple, reducing the LA high-frequency current and ripple cancellation current, improving the overall system ef?ciency. A slew-rate enhancement (SRE) circuit is employed in the LA, resulting in slew rate of over 307 V/μs and bandwidth of over 275 MHz for the LA. The SRE circuit provides a parallel auxiliary current path directly to the gate of the class-AB output stage transistors, speeding-up the charging or discharging of output without modifying the operating point of the remaining LA, while maintaining the quiescent current of the class-AB stage. The supply modulator is fabricated in a 65-nm CMOS process. The measurement results show the tracking of long-term evolution (LTE)-40-MHz envelope with 93% peak ef?ciency at 1-W output power, while the SRE is disabled. Enabling the SRE, it can track LTE-80-MHz envelope with peak ef?ciency of 91%.
关键词： long-term evolution (LTE),LTE-advanced,hysteresis control,Envelope tracking (ET),supply modulator,power ampli?er (PA),three-level switching converter (3L-SWC),slew-rate enhancement (SRE),hybrid
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Highly Accelerated Thermal Cycling Test for New Type of Crystalline Silicon Photovoltaic Modules
摘要： We present the main results of the performance test campaign of the Mid-Infrared European Extremely Large Telescope Imager and Spectrograph (METIS) Cold Chopper Demonstrator (MCCD). This tip/tilt mirror, which operates at a temperature of 77 K, is one of the critical components in the METIS for the European Extremely Large Telescope. The performance requirements of the MCCD relate to the field of fast and very accurate reference tracking. We discuss the applicability of different high-performance motion control strategies and describe the control synthesis of a repetitive and of a novel hybrid controller. We identified the presence of nonlinearities in the plant, which limits the performance of the hybrid controller. The repetitive controller shows very promising results and can handle the nonlinearities in the system. This experimental phase concludes the MCCD program, which was initiated to verify the feasibility of a high-performance cryogenic tip/tilt mirror at an early stage in the METIS development. Because of the very promising test results, no significant changes to the hardware will be implemented. We believe that minor adjustments will suffice to meet all requirements of the final hardware after integration with the METIS instrument.
关键词： motion control,repetitive control,hysteresis,hybrid control,control synthesis,high-performance,tip/tilt mechanism
更新于2025-09-19 17:13:59
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Enhanced Interfacial Binding and Electron Extraction Using Boron‐Doped TiO <sub/>2</sub> for Highly Efficient Hysteresis‐Free Perovskite Solar Cells
摘要： Perovskite solar cells (PSCs) have witnessed astonishing improvement in power conversion efficiency (PCE), more recently, with advances in long-term stability and scalable fabrication. However, the presence of an anomalous hysteresis behavior in the current density–voltage characteristic of these devices remains a key obstacle on the road to commercialization. Herein, sol–gel-processed mesoporous boron-doped TiO2 (B-TiO2) is demonstrated as an improved electron transport layer (ETL) for PSCs for the reduction of hysteresis. The incorporation of boron dopant in TiO2 ETL not only reduces the hysteresis behavior but also improves PCE of the perovskite device. The simultaneous improvements are mainly ascribed to the following two reasons. First, the substitution of under-coordinated titanium atom by boron species effectively passivates oxygen vacancy defects in the TiO2 ETL, leading to increased electron mobility and conductivity, thereby greatly facilitating electron transport. Second, the boron dopant upshifts the conduction band edge of TiO2, resulting in more efficient electron extraction with suppressed charge recombination. Consequently, a methylammonium lead iodide (MAPbI3) photovoltaic device based on B-TiO2 ETL achieves a higher efficiency of 20.51% than the 19.06% of the pure TiO2 ETL based device, and the hysteresis is reduced from 0.13% to 0.01% with the B-TiO2 based device showing negligible hysteresis behavior.
关键词： perovskite solar cells,hysteresis,interfacial binding,charge transport,titanium dioxide
更新于2025-09-19 17:13:59
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Unusual Bimodal Photovoltaic Performance of Perovskite Solar Cells at Real-World Operating Temperatures
摘要： A deep understanding of environmental effects on perovskite solar cell (PSC) performance is highly desirable for further progress towards large-scale deployment of this technology. We investigate the operation of PSCs in the temperature range (15?50 C) and report an unusual bimodal behavior in photovoltaic (PV) performance, with positive and negative temperature coefficients (TCs) below and above room temperature (RT), respectively. Furthermore, the performance metrics exhibit hysteresis, as their values depend on whether the measurements are made during the heating or cooling stages of the experiment. Conventional semiconductor solar cells, in contrast, exhibit a monotonic and non-hysteretic performance decline in this temperature range. The variations in power conversion efficiency primarily follow changes in open-circuit voltage and fill factor. Photoluminescence data suggest that the performance variations below RT are accompanied by a reduction in defect-related traps in the perovskite absorber and a drop in interfacial built-in potential at the perovskite/transport layer interface. The behavior above RT follows the conventional trend and can hence be explained by charge-phonon interactions. Our findings offer significant insight into the salient PV properties and photophysics of perovskite materials that define their performance in the real-world operating temperature range.
关键词： charge-phonon coupling,temperature-dependent hysteresis,Perovskite solar cells,Temperature coefficient
更新于2025-09-19 17:13:59
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A universal strategy combining interface and grain boundary engineering for negligible hysteresis and high efficiency (21.41%) planar perovskite solar cells
摘要： Planar perovskite solar cells (PSCs) release the potential to compete with mesoporous PSCs because of comparable power conversion efficiency (PCE) and compatible with the preparation of flexible or tandem PSCs. However, the severe current-voltage hysteresis occurring in PSCs is still a big issue, attributable to the trap-induced charge recombination and ion migration. Herein, we develop a universal strategy combining interface (PMMA:C60) and grain boundary (PTABr) engineeing to effectively eliminate hysteresis of planar PSCs by finely tuning the electron transport layer/perovskite interface and perovskite film morphology (grain size and grain boundary). Microstructure and spectra characterizations, density functional theory (DFT) calculations and photoelectric measurements reveal that this ingenious combination of the two engineering approaches effectively reduce the trap sites and enlarge perovskite grain size, hence leading to negligible hysteresis and high performance PSCs based on various compositional perovskites including MAPbI3, Cs0.15FA0.85PbI3 and Cs0.15FA0.75MA0.1PbI3, with PCE of 18.99%, 19.82%, 21.41% and extra-low hysteresis index of 0.011, 0.007, 0.005, respectively. This work demonstrates a universal strategy to fabricate high efficiency and negligible hysteresis PSCs regardless of perovskite composition.
关键词： hysteresis,power conversion efficiency,grain boundary engineering,interface engineering,perovskite solar cells
更新于2025-09-19 17:13:59
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[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Aperture-coupled Plasmonic Voltage Tunable Filter Based on Asymmetric Micro-ring Resonators
摘要： This paper presents a novel mixed-signal low-power dual-band square/triangular waveform generator (WFG) chip with a wide low-frequency tuning range for medical bio-electric stimulation therapy. It consists of a relaxation oscillator comprising a hysteresis Schmitt trigger and a timing integrator, along with frequency divider (FD) stages and path selector output for driving an electrode from 16 selectable channels. It was fabricated using Global Foundries 8RF-DM 130-nm CMOS process with a supply voltage of ±1 V for the oscillator and +1 V for logic circuits. The WFG provides an output of around 1.5 Vp–p at a nominal low oscillation frequency of 17 kHz using small-size on-chip passive components of values 10 kΩ and 10 pF. The WFG core (band I) can be tuned in the range 6.44–1003 kHz through bias current adjustment, while a lower frequency (band II) in the range 0.1 Hz–502 kHz can be provided digitally through a ÷2 stage. The power consumption was only 0.457 mW for the WFG and 2.1 mW for the FD circuit while occupying a total silicon area of only 18 426 μm2.
关键词： hysteresis Schmitt trigger,low-frequency,multiplexer,path selector,frequency divider,low-power,Waveform generator
更新于2025-09-19 17:13:59
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Correlating Hysteresis and Stability with Organic Cation Composition in the Two-Step Solution-Processed Perovskite Solar Cells
摘要： The two-step solution-based process has demonstrated substantial success in fabricating high-efficiency perovskite solar cells in recent years. Despite the high performance, the underlying mechanisms that govern the formation of perovskite films and corresponding device performance are yet to be fully understood. Particularly, organic cation composition used in the two-step solution processing of mixed-cation lead halide perovskite solar cells plays a critical role in the perovskite film formation and the resultant device performance. However, little is understood about the impacts of organic cation composition on the current density-voltage (J-V) hysteretic behavior and stability of perovskite solar cells. To address this need, here, we study the effect of mixed organic cations, i.e., the fraction of formamidinium (FA) and methylammonium (MA) contents, used for the two-step solution-processed perovskite thin films on solar cell performance, including efficiency, J-V hysteresis, and stability. In addition to the efficiency variations, we find that perovskite solar cells based on FA-rich and MA-rich stoichiometries show distinct characteristics in J-V hysteresis and stability. The origins of such a discrepancy are attributed to the thermodynamically driven conversion from lead iodide to perovskites, which is determined by the combination of organic cations. The perovskite solar cells based on the mixed cation FA0.6MA0.4PbI3 composition show a champion power conversion efficiency of over 21% and robust stability (retaining more than 90% of initial efficiency) under maximum power point tracking in dry nitrogen for more than 500 hours. Our work provides insights on understanding the formation of perovskite films in the two-step process, which may benefit further investigation on perovskite solar cells.
关键词： stability,Perovskite solar cells,two-step process,J-V hysteresis,organic cation composition
更新于2025-09-19 17:13:59