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RISS 인기검색어
- 검색키워드
- 주제어 : Lifetime of excitons (검색결과 8 건)
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Charge Carriers and Excitons Transport in an Organic Solar Cell-Theory and Simulation
Ali. Shahini,Karim. Abbasian 대한금속·재료학회 2012 ELECTRONIC MATERIALS LETTERS Vol.8 No.4
An organic solar cell model is developed that consists of both excitonic and classical bipolar aspects of solar cells. In order to achieve this goal, the photon recycling term is imported into the equations to connect the Shockley-Queisser theory and the classical diode theory. This model for excitonic and classical bipolar solar cells can describe the combined transport and interaction of electrons, holes and excitons. For high mobilities this model reproduces the Shockley Queisser efficiency limit. We show how varying the respective mobilities of the different species changes the operation mode of the solar cell path between excitonic and bipolar. Then, the effect of conduction band offset on transport will be described in this paper. Finally, validity of reciprocity theorem between quantum efficiency and electroluminescence in this model will be discussed.
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Calculation of the radiative lifetime of Wannier-Mott excitons in nanoclusters
Kukushkin, Vladimir A. Techno-Press 2013 Advances in nano research Vol.1 No.3
This study is aimed to calculate the radiative lifetime of Wannier-Mott excitons in nanoclusters of a narrow-bandgap semiconductor embedded in a wide-bandgap one. The nanocluster linear dimensions are assumed to be much larger than the radius of the exciton so that the latter is not destructed by the confinement potential as it takes place in small quantum dots. The calculations were carried out for an example of InAs nanoclusters put into the GaAs matrix. It is shown that the radiative lifetime of Wannier-Mott excitons in such clusters increases with the decrease of the cluster dimensions, this tendency being more pronounced at low temperatures. So, the creation of excitons in nanoclusters of a narrow-bandgap material embedded in a wide-bandgap one can be used to significantly prolong their radiative lifetime in comparison with that of excitons in a bulk semiconductor.
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Jeon, S.K.,Lee, J.Y. Elsevier Science 2015 ORGANIC ELECTRONICS Vol.27 No.-
Lifetime of blue phosphorescent organic light-emitting diodes (OLEDs) was improved by suppressing a recombination zone shift using a high triplet energy exciton blocking layer. Host material of the emitting layer was inserted as the exciton blocking layer between a hole transport layer and an emitting layer, and the exciton blocking layer kept the recombination zone near hole transport layer side without significant emission zone change during lifetime test. The suppressed recombination zone shift improved the lifetime of the blue phosphorescent OLED by four times.
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최정민,이준엽 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0
Blue phosphorescent organic light-emitting diodes (PHOLEDs) with high efficiency and lifetime were developed by exciton harvesting layer at electron transport layer. A green emitter doped electron transport layer was able to harvest the triplet exciton in the blue PHOLEDs, which improved the lifetime and the efficiency of the blue PHOLEDs compared with a common electron transport layer. The exciton harvesting layer blocked blue triplet emitter from triplet exciton quenching.
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The electrical and valley properties of monolayer MoSe2
김동학,임대영 한국물리학회 2017 Current Applied Physics Vol.17 No.2
We studied the electrical, optical and valley properties of monolayer MoSe2. The measured PL circular polarization of monolayer MoSe2 was negligibly small, compared with the more-than 60% circular polarization of monolayer MoS2. Doping-dependent PL measurement and Kelvin probe microscopy show that the small circular polarization because of its longer exciton lifetime in monolayer MoSe2. Furthermore, it is found that the longer exciton lifetime is due to the nearly intrinsic electrical property of monolayer MoSe2, where non-radiative trion decay, which is the dominant exciton decay mechanism in n-type monolayer MoS2, is minimized due to the low density of excess electrons (holes). We believe that S and Se vacancies play an important role in determining the Fermi level position for these materials. Our experimental results show that monolayer MoSe2 can be a better valleytronics material than monolayer MoS2 in spite of its small circular polarization.
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The electrical and valley properties of monolayer MoSe<sub>2</sub>
Kim, Dong Hak,Lim, D. Elsevier 2017 Current Applied Physics Vol.17 No.2
<P>We studied the electrical, optical and valley properties of monolayer MoSe2. The measured PL circular polarization of monolayer MoSe2 was negligibly small, compared with the more-than 60% circular polarization of monolayer MoSe2. Doping-dependent PL measurement and Kelvin probe microscopy show that the small circular polarization because of its longer exciton lifetime in monolayer MoSe2. Furthermore, it is found that the longer exciton lifetime is due to the nearly intrinsic electrical property of monolayer MoSe2, where non-radiative trion decay, which is the dominant exciton decay mechanism in n-type monolayer MoSe2, is minimized due to the low density of excess electrons (holes). We believe that S and Se vacancies play an important role in determining the Fermi level position for these materials. Our experimental results show that monolayer MoSe2 can be a better valleytronics material than monolayer MoSe2 in spite of its small circular polarization. (C) 2016 Elsevier B.V. All rights reserved.</P>
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Self-Assembled InGaAs Quantum Dot Clusters with Controlled Spatial and Spectral Properties
Creasey, Megan,Lee, Ji-Hoon,Wang, Zhiming,Salamo, Gregory J.,Li, Xiaoqin American Chemical Society 2012 Nano letters Vol.12 No.10
<P>Planar quantum dot clusters (QDCs) consisting of six InGaAs quantum dots (QDs) formed around a GaAs nanomound are the most sophisticated self-assembled QDCs grown by molecular beam epitaxy thus far. We present the first photoluminescence measurements on individual hexa-QDCs with high spatial, spectral, and temporal resolution. In the best QDCs, the excitons confined in individual QDs are remarkably close in energy, exhibiting only a 10 meV spread. In addition, a biexponential decay profile and small variation in decay rates for different QDs was observed. The homogeneous energetics and dynamics suggest that the sizes, shapes, and composition of the QDs within these clusters are highly uniform.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2012/nalefd.2012.12.issue-10/nl3021736/production/images/medium/nl-2012-021736_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl3021736'>ACS Electronic Supporting Info</A></P>
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Optical Properties of a Quantum Dot-Ring System Grown Using Droplet Epitaxy
Linares-Garcí,a, Gabriel,Meza-Montes, Lilia,Stinaff, Eric,Alsolamy, S. M.,Ware, M. E.,Mazur, Y. I.,Wang, Z. M.,Lee, Jihoon,Salamo, G. J. Springer US 2016 NANOSCALE RESEARCH LETTERS Vol.11 No.1
<P>Electronic and optical properties of InAs/GaAs nanostructures grown by the droplet epitaxy method are studied. Carrier states were determined by <B>k</B><B>·</B><B>p</B> theory including effects of strain and In gradient concentration for a model geometry. Wavefunctions are highly localized in the dots. Coulomb and exchange interactions are studied and we found the system is in the strong confinement regime. Microphotoluminescence spectra and lifetimes were calculated and compared with measurements performed on a set of quantum rings in a single sample. Some features of spectra are in good agreement.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1186/s11671-016-1518-2) contains supplementary material, which is available to authorized users.</P>
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