About twenty years ago, in the autumn of 1996, the first white light-emitting diodes (LEDs) were offered for sale. These then-new devices ushered in a new era in lighting by displacing lower-efficiency conventional light sources including Edison's venerable incandescent lamp as well as the Hg-discharge-based fluorescent lamp. We review the history of the conception, improvement, and commercialization of the white LED. Early models of white LEDs already exceeded the efficiency of low-wattage incandescent lamps, and extraordinary progress has been made during the last 20 years. The review also includes a discussion of advances in blue LED chips, device architecture, light extraction, and phosphors. Finally, we offer a brief outlook on opportunities provided by smart LED technology.

White light-emitting diodes: History, progress, and future

Silicon wafer solar cells continue to be the leading photovoltaic technology, and in many places are now providing a substantial portion of electricity generation. Further adoption of this technology will require processing that minimises losses in device performance. A fundamental mechanism for efficiency loss is the recombination of photo-generated charge carriers at the unavoidable cell surfaces. Dielectric coatings have been shown to largely prevent these losses through a combination of different passivation mechanisms. This review aims to provide an overview of the dielectric passivation coatings developed in the past two decades using a standardised methodology to characterise the metrics of surface recombination across all techniques and materials. The efficacy of a large set of materials and methods has been evaluated using such metrics and a discussion on the current state and prospects for further surface passivation improvements is provided.

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Dielectric surface passivation for silicon solar cells: A review

Article History: Purpose: The present study aims to investigate the level of teachers' organizational citizenship behaviors and counter-productive work behaviors (CWBs) based on public primary school administrators’ and teachers' perceptions and the relationship between these two variables. Research Methods: This study was conducted in a correlational survey model. The sample of this study was formed in the 2018-2019 academic year, consisted of public primary school administrators and teachers who worked in nine different districts Received: 18 Jun., 2019 Received in revised form: 22 Sept. 2019 Accepted: 14 Oct. 2019 DOI: 10.14689/ejer.2019.84.1

Eurasian Journal of Educational Research

Nanoparticles-based magnetic and photo induced hyperthermia for cancer treatment

We report on spin Hall magnetoresistance (SMR) measurements of Pt Hall bars on antiferromagnetic NiO(111) single crystals. An SMR with a sign opposite to conventional SMR is observed over a wide range of temperatures as well as magnetic fields stronger than 0.25 T. The negative sign of the SMR can be explained by the alignment of magnetic moments being almost perpendicular to the external magnetic field within the easy plane (111) of the antiferromagnet. This correlation of magnetic moment alignment and the external magnetic field direction is realized just by the easy-plane nature of the material without the need of any exchange coupling to an additional ferromagnet. The SMR signal strength decreases with increasing temperature, primarily due to the decrease in Neel order by including fluctuations. An increasing magnetic field increases the SMR signal strength as there are fewer domains, and the magnetic moments are more strongly manipulated at high magnetic fields. The SMR is saturated at an applied magnetic field of 6 T, resulting in a spin-mixing conductance of similar to 10(18) Omega(-1) m(-2), which is comparable to that of Pt on insulating ferrimagnets such as yttrium iron garnet. An argon plasma treatment doubles the spin-mixing conductance. Published by AIP Publishing.

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Negative spin Hall magnetoresistance of Pt on the bulk easy-plane antiferromagnet NiO

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/pdf/seoul-sojae-7gae-jonghabbyeongweon-amhwanjadeulyi-2y5bbrkske.pdf

김순덕 ( Soon Duck Kim )

Papers

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