There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

The photovoltaics of organic–inorganic lead halide perovskite materials have shown rapid improvements in solar cell performance, surpassing the top efficiency of semiconductor compounds such as CdTe and CIGS (copper indium gallium selenide) used in solar cells in just about a decade. Perovskite preparation via simple and inexpensive solution processes demonstrates the immense potential of this thin-film solar cell technology to become a low-cost alternative to the presently commercially available photovoltaic technologies. Significant developments in almost all aspects of perovskite solar cells and discoveries of some fascinating properties of such hybrid perovskites have been made recently. This Review describes the fundamentals, recent research progress, present status, and our views on future prospects of perovskite-based photovoltaics, with discussions focused on strategies to improve both intrinsic and extrinsic (environmental) stabilities of high-efficiency devices. Strategies and challenges regardi...

Halide Perovskite Photovoltaics: Background, Status, and Future Prospects

This review article attempts to provide a comprehensive review of the recent progress in the so-called resistive random access memories (RRAMs) First, a brief introduction is presented to describe the construction and development of RRAMs, their potential for broad applications in the fields of nonvolatile memory, unconventional computing and logic devices, and the focus of research concerning RRAMs over the past decade Second, both inorganic and organic materials used in RRAMs are summarized, and their respective advantages and shortcomings are discussed Third, the important switching mechanisms are discussed in depth and are classified into ion migration, charge trapping/de-trapping, thermochemical reaction, exclusive mechanisms in inorganics, and exclusive mechanisms in organics Fourth, attention is given to the application of RRAMs for data storage, including their current performance, methods for performance enhancement, sneak-path issue and possible solutions, and demonstrations of 2-D and 3-D crossbar arrays Fifth, prospective applications of RRAMs in unconventional computing, as well as logic devices and multi-functionalization of RRAMs, are comprehensively summarized and thoroughly discussed The present review article ends with a short discussion concerning the challenges and future prospects of the RRAMs

Recent progress in resistive random access memories: Materials, switching mechanisms, and performance

A Review of Perovskites Solar Cell Stability

High‐Performance Planar Perovskite Solar Cells Using Low Temperature, Solution–Combustion‐Based Nickel Oxide Hole Transporting Layer with Efficiency Exceeding 20%

In this work, a simple and efficient method for the extraction of all the parameters of a solar cell from a single current-voltage (I-V) curve under the constant illumination level is proposed. With the help of the Lambert W function, the explicit analytic expression for I is obtained. By reducing the number of the parameters, the expression for I only depends on the ideality factor n, the series resistance Rs, and the shunt resistance Rsh. This analytic expression is directly used to fit the experimental data and extract the device parameters. This simple solar cell parameter extraction method can be directly applied for all kinds of solar cells whose I-V characteristics follow the single-diode model. The parameters of various solar devices including silicon solar cells, silicon solar modules, dye-sensitized solar cells, and organic solar cells with standalone, tandem, and multi-junction structures have been successfully extracted by using our proposed method.

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A simple and efficient solar cell parameter extraction method from a single current-voltage curve

Intermolecular Exchange Boosts Efficiency of Air-Stable, Carbon-Based All-Inorganic Planar CsPbIBr2 Perovskite Solar Cells to Over 9%

We report the first ferroelectric (FE) HfZrO x (HZO) Ge and GeSn pMOSFETs with sub-60 mV/decade subthreshold swing (SS) (40∼43 mV/decade), negligible hysteresis, and enhanced Ids. With a RTA at 450 oC, FE devices with reduced hysteresis of 40∼60 mV demonstrate the significantly improved SS and I ds characteristics compared to control devices without FE, owing to the negative capacitance (NC) effect induced by HZO. FE Ge and GeSn pFETs achieve 22% and 20% I ds enhancement than control devices, respectively, at the drive voltage of 1.0 V. NC effect in FE devices is proved by the gate leakage and inversion capacitance characteristics.

Ferroelectric HfZrO x Ge and GeSn PMOSFETs with Sub-60 mV/decade subthreshold swing, negligible hysteresis, and improved I ds

Perovskite solar cells (PSCs) have attracted much attention due to their impressive photovoltaic performance and low fabrication cost. The perovskite layer plays a critical role in light-to-electricity conversion. Here we study the effects of alkali metal ion dopants on the growth, structure and properties of perovskite films and the photovoltaic performance of PSCs. At a low doping level, the alkali metal ions can significantly affect the formation and properties of the perovskite films. They can enhance the short-circuit current density (Jsc) and power conversion efficiency (PCE) significantly. The Jsc increases significantly from 19.2 mA cm−2 to 21.0 mA cm−2 and 20.3 mA cm−2 for the PSCs with a methylammonium lead triode layer doped with 0.5 mol% K+ and 0.25 mol% Na+, respectively, and the fill factor (FF) increases from 0.74 to 0.79 for the devices with both doping ions. Correspondingly, the PCE increases from 13.7% to 15.3% and 14.6% for the PSCs, respectively. The efficiency improvement by K+ or Na+ doping is attributed to their effect in increasing the crystallinity and crystallite size of the perovskite films.

Chunfu Zhang

Papers

High‐Performance Planar Perovskite Solar Cells Using Low Temperature, Solution–Combustion‐Based Nickel Oxide Hole Transporting Layer with Efficiency Exceeding 20%

A simple and efficient solar cell parameter extraction method from a single current-voltage curve

Intermolecular Exchange Boosts Efficiency of Air-Stable, Carbon-Based All-Inorganic Planar CsPbIBr2 Perovskite Solar Cells to Over 9%

Ferroelectric HfZrO x Ge and GeSn PMOSFETs with Sub-60 mV/decade subthreshold swing, negligible hysteresis, and improved I ds

Enhancing the photovoltaic performance of planar heterojunction perovskite solar cells by doping the perovskite layer with alkali metal ions