scholarly journals Dark exciton anti-funneling in atomically thin semiconductors

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Roberto Rosati ◽  
Robert Schmidt ◽  
Samuel Brem ◽  
Raül Perea-Causín ◽  
Iris Niehues ◽  
...  
Keyword(s):  
Electric Fields ◽  
Microscopic Theory ◽  
Strain Engineering ◽  
Charge Carriers ◽  
Major Advance ◽  
Electron Hole ◽  
Electrical Fields ◽  
Exciton Transport ◽  
Time Space ◽  
Dark Exciton

AbstractTransport of charge carriers is at the heart of current nanoelectronics. In conventional materials, electronic transport can be controlled by applying electric fields. Atomically thin semiconductors, however, are governed by excitons, which are neutral electron-hole pairs and as such cannot be controlled by electrical fields. Recently, strain engineering has been introduced to manipulate exciton propagation. Strain-induced energy gradients give rise to exciton funneling up to a micrometer range. Here, we combine spatiotemporal photoluminescence measurements with microscopic theory to track the way of excitons in time, space and energy. We find that excitons surprisingly move away from high-strain regions. This anti-funneling behavior can be ascribed to dark excitons which possess an opposite strain-induced energy variation compared to bright excitons. Our findings open new possibilities to control transport in exciton-dominated materials. Overall, our work represents a major advance in understanding exciton transport that is crucial for technological applications of atomically thin materials.

Nanostructured Organic–Inorganic Hybrid Solar Cells

MRS Bulletin ◽  
2009 ◽  
Vol 34 (2) ◽  
pp. 95-100 ◽  
Author(s):  
Michael D. McGehee
Keyword(s):  
Solar Cells ◽  
Organic Semiconductors ◽  
Charge Carriers ◽  
Hybrid Solar Cells ◽  
Electron Hole ◽  
Inorganic Hybrid ◽  
Oxide Electrodes ◽  
Exciton Transport ◽  
Ordered Nanostructures ◽  
Bound Electron

AbstractWhen light is absorbed in organic semiconductors, bound electron–hole pairs known as excitons are generated. The electrons and holes separate from each other at an interface between two semiconductors by electron transfer. It is advantageous to form well-ordered nanostructures so that all of the excitons can reach the interface between the two semiconductors and all of the charge carriers have a pathway to the appropriate electrode. This article discusses charge and exciton transport in organic semiconductors, as well as the opportunities for making highly efficient solar cells and for using carbon nanotubes to replace metal oxide electrodes.

Current Status of Solid-State X-Ray Systems

1985 ◽  
Vol 43 ◽  
pp. 158-161
Author(s):  
Martin Peckerar ◽  
Anastasios Tousimis
Keyword(s):  
Solid State ◽  
Electric Fields ◽  
Spectral Lines ◽  
Current Status ◽  
Mobile Charge ◽  
Electron Hole ◽  
X Ray ◽  
Sensing Systems ◽  
Transmission Electron ◽  
Electron Microscopes

Solid state x-ray sensing systems have been used for many years in conjunction with scanning and transmission electron microscopes. Such systems conveniently provide users with elemental area maps and quantitative chemical analyses of samples. Improvements on these tools are currently sought in the following areas: sensitivity at longer and shorter x-ray wavelengths and minimization of noise-broadening of spectral lines. In this paper, we review basic limitations and recent advances in each of these areas. Throughout the review, we emphasize the systems nature of the problem. That is. limitations exist not only in the sensor elements but also in the preamplifier/amplifier chain and in the interfaces between these components.Solid state x-ray sensors usually function by way of incident photons creating electron-hole pairs in semiconductor material. This radiation-produced mobile charge is swept into external circuitry by electric fields in the semiconductor bulk.

scholarly journals Visible emission from Er-doped SnO2 thin films deposited by sol-gel

Cerâmica ◽  
2007 ◽  
Vol 53 (326) ◽  
pp. 187-191 ◽  
Author(s):  
L. P. Ravaro ◽  
E. A. Morais ◽  
L. V. A. Scalvi ◽  
M. Siu Li
Keyword(s):  
Thin Film ◽  
Electric Fields ◽  
Tin Dioxide ◽  
Sol Gel ◽  
Precursor Solution ◽  
Dip Coating ◽  
Sno2 Thin Film ◽  
Rare Earth Ion ◽  
Electron Hole ◽  
Er Doped

Emission from Er-doped SnO2 thin film deposited via sol-gel by the dip coating technique is obtained in the range 500-700 nm with peak at 530 nm (green). Electron-hole generation in the tin dioxide matrix is used to promote the rare-earth ion excitation. Evaluation of crystallite dimensions through X-ray diffraction results leads to nanoscopic size, what could play a relevant role in the emission spectra. The electron-hole mechanism is also responsible for the excitation of the transition in the 1540 nm range in powders obtained from the same precursor solution of films. The thin film matrix presents a very useful shape for technological application, since it allows integration in optical devices and the application of electric fields to operate electroluminescent devices.

Strain-engineering the in-plane electrical anisotropy of GeSe monolayers

2020 ◽  
Vol 22 (2) ◽  
pp. 914-918 ◽  
Author(s):  
Zongbao Li ◽  
Xinsheng Liu ◽  
Xia Wang ◽  
Yusi Yang ◽  
Shun-Chang Liu ◽  
...  
Keyword(s):  
Effective Mass ◽  
Strain Engineering ◽  
Charge Carriers ◽  
Electrical Anisotropy ◽  
Mobility Of Charge Carriers

The anisotropic ratio of the effective mass and mobility of charge carriers of GeSe monolayer along two principle axes can be controlled by using simple strain conditions.

scholarly journals Semicircular Patch-Embedded Vivaldi Antenna for Miniaturized UWB Radar Sensors

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 5988
Author(s):  
Jungwoo Seo ◽  
Jae Hee Kim ◽  
Jungsuek Oh
Keyword(s):  
Electric Fields ◽  
Impedance Matching ◽  
Low Frequency ◽  
Electrical Fields ◽  
Radar Sensors ◽  
Gain Enhancement ◽  
Uwb Radar ◽  
Vivaldi Antenna ◽  
Matching Techniques ◽  
Good Agreement

A microstrip-to-slot line-fed miniaturized Vivaldi antenna using semicircular patch embedment is proposed in this study. The conventional Vivaldi antenna has ultrawide bandwidth, but suffers from low gain in the low-frequency band. The proposed antenna topology incorporates the embedment of semicircular patch elements into the side edge of the antenna. This enables the phases of electric fields at both ends of the antenna to be out of phase. Since the distance between the two ends are λL/2 where λL is the wavelength at a low operating frequency, this antenna topology can achieve the constructive addition of electrical fields at the radiating end, leading to gain enhancement at the chosen low frequency. In comparison with the conventional Vivaldi antenna, the proposed antenna has a wider bandwidth from 2.84 to 9.83 GHz. Moreover, the simulated result shows a gain enhancement of 5 dB at low frequency. This cannot be realized by the conventional low-band impedance matching techniques only relying on slotted topologies. The measured results of this proposed antenna with a size of 45 × 40 × 0.8 mm3 are in good agreement with the simulated results.

scholarly journals Plasmon-Induced Electrocatalysis with Multi-Component Nanostructures

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 43 ◽  
Author(s):  
Palaniappan Subramanian ◽  
Dalila Meziane ◽  
Robert Wojcieszak ◽  
Franck Dumeignil ◽  
Rabah Boukherroub ◽  
...  
Keyword(s):  
Heterogeneous Catalysts ◽  
Charge Carriers ◽  
Catalytic Reactions ◽  
Synthetic Methods ◽  
Metal Nanostructures ◽  
Electron Hole ◽  
Catalytic Systems ◽  
Electrochemical Catalysis ◽  
Electrochemically Active ◽  
Shed Light

Noble metal nanostructures are exceptional light absorbing systems, in which electron–hole pairs can be formed and used as “hot” charge carriers for catalytic applications. The main goal of the emerging field of plasmon-induced catalysis is to design a novel way of finely tuning the activity and selectivity of heterogeneous catalysts. The designed strategies for the preparation of plasmonic nanomaterials for catalytic systems are highly crucial to achieve improvement in the performance of targeted catalytic reactions and processes. While there is a growing number of composite materials for photochemical processes-mediated by hot charge carriers, the reports on plasmon-enhanced electrochemical catalysis and their investigated reactions are still scarce. This review provides a brief overview of the current understanding of the charge flow within plasmon-enhanced electrochemically active nanostructures and their synthetic methods. It is intended to shed light on the recent progress achieved in the synthesis of multi-component nanostructures, in particular for the plasmon-mediated electrocatalysis of major fuel-forming and fuel cell reactions.

scholarly journals Upgrade of the YerPhI polarization Lidar System for using Polarization of the Elastic and Raman Backscattered Beams

2019 ◽  
Vol 197 ◽  
pp. 03005
Author(s):  
A. Ghalumyan ◽  
K. Apresyan ◽  
A. Chilingaryan ◽  
V. Ghazaryan
Keyword(s):  
Electric Fields ◽  
Gamma Ray ◽  
Beam Polarization ◽  
Lidar System ◽  
Density Profiles ◽  
Electrical Fields ◽  
Polarized Beams ◽  
Electrical State ◽  
Atmospheric Backscatter ◽  
Telescope System

A powerful two-frequency lidar system using polarized beams has been developed at YerPhI. The system is completed with laser beam polarization changers and nitrogen and water Raman channels for investigation of the influence of atmospheric electric fields on the elastic and Raman backscattered beams polarization. At present, the system is being tuned for measuring vertical atmospheric backscatter profiles of aerosols and hydrometeors, analyze the depolarization ratio of elastic backscattered laser beams and investigate the influence of external factors on the beam polarization. Laser light that is reflected from the air and from clouds carries information on density profiles, aerosols and electrical fields. Applications of this system will be the investigation of the electrical state of the atmosphere during thunderstorms [1-3] on Mt Aragats, and, possibly the monitoring of the atmosphere at the site of the upcoming Cherenkov Telescope Array (CTA). CTA is expected to provide unprecedented sensitivity for gamma ray detection in the energy range of 30 GeV to 300 TeV. To fully exploit the potential of the telescope system it is important to characterize the optical and electrical properties of the atmosphere. A lidar system for the continuous monitoring of the atmosphere is the tool of choice.

scholarly journals Photocatalytic water splitting by N-TiO2 on MgO (111) with exceptional quantum efficiencies at elevated temperatures

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Yiyang Li ◽  
Yung-Kang Peng ◽  
Liangsheng Hu ◽  
Jianwei Zheng ◽  
Dharmalingam Prabhakaran ◽  
...  
Keyword(s):  
Water Splitting ◽  
Elevated Temperatures ◽  
Practical Method ◽  
Charge Carriers ◽  
Molar Ratio ◽  
Electron Hole ◽  
Photocatalytic Water Splitting ◽  
The Past ◽  
Electron Hole Pair ◽  
Electric Field Polarization

Abstract Photocatalytic water splitting is attracting enormous interest for the storage of solar energy but no practical method has yet been identified. In the past decades, various systems have been developed but most of them suffer from low activities, a narrow range of absorption and poor quantum efficiencies (Q.E.) due to fast recombination of charge carriers. Here we report a dramatic suppression of electron-hole pair recombination on the surface of N-doped TiO2 based nanocatalysts under enhanced concentrations of H+ and OH−, and local electric field polarization of a MgO (111) support during photolysis of water at elevated temperatures. Thus, a broad optical absorption is seen, producing O2 and H2 in a 1:2 molar ratio with a H2 evolution rate of over 11,000 μmol g−1 h−1 without any sacrificial reagents at 270 °C. An exceptional range of Q.E. from 81.8% at 437 nm to 3.2% at 1000 nm is also reported.

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