http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Efficiency limit of InAs/GaAs quantum dot solar cells attributed to quantum dot size effects
Han, Im Sik,Smith, Ryan P.,Kim, Jong Su,Noh, Sam Kyu,Lee, Sang Jun,Lee, Chang-Lyoul,Leem, Jae-Young Elsevier 2016 Solar energy materials and solar cells Vol.155 No.-
<P><B>Abstract</B></P> <P>The effects of quantum dot (QD) size on the optical and electrical properties of InAs/GaAs QD solar cells (QDSCs) were investigated. QDSCs with varying InAs QD size were fabricated by controlling the total InAs deposition thickness (<I>θ</I>) from 0 to 3.0 mono-layers (ML). The optical and electrical properties of the QDSCs were investigated using photoluminescence (PL), time-resolved PL (TRPL), photoreflectance (PR) spectroscopy, capacitance-voltage (<I>C</I>-<I>V</I>), and current-voltage (<I>J-V</I>) measurements. The QD size effects on the p-n junction electric fields (<I> <B>F</B> </I> <SUB> <I> <B>pn</B> </I> </SUB>) and the efficiencies (<I>η</I>) of the QDSCs were revealed. The QDSCs had a maximum <I>η</I> of 21.17% for <I>θ</I>=2.0ML (the efficiency is enhanced by 17.4% over the reference GaAs-SC) and minimized <I> <B>F</B> </I> <SUB> <I> <B>pn</B> </I> </SUB> (113kV/cm) by an enhanced photovoltaic effect caused by improved carrier generation. We find that these optimal properties result from a balance between carrier generation and exhaustion processes through trapping and re-capturing by defects and relatively large QDs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The effect of quantum dot (QD) size on the optical and electrical properties of InAs/GaAs QD solar cells (QDSCs) was investigated. </LI> <LI> The QD size effects on the p-n junction electric fields (<I>F</I> <SUB> <I>pn</I> </SUB>) and the efficiencies (<I>η</I>) of the QDSCs were revealed. </LI> <LI> The QD size affects <I>η</I> and <I>F</I> <SUB> <I>pn</I> </SUB> due to the balance between the carrier generation and exhaustion processes through trapping and re-capturing. </LI> </UL> </P>
손창원,한임식,Ryan P. Smith,김종수,노삼규,최현광,임재영 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.7
We investigated the optical and the electrical properties of GaAs solar cells (SCs) by usingphotoreflectance (PR) spectroscopy and current-voltage (J-V) measurements. The electric fields(Fj) in p-n junctions were evaluated through an analysis of the Franz-Keldysh oscillations (FKOs)of the PR spectra. From the excitation light intensity (Iex) dependence of the PR, we found thatthe photovoltaic effect resulted in a reduction of the Fj . The Fj was gradually reduced by up to37% from the dark built-in electric field when the Iex was increased (Iex = 2.3 181 mW/cm2). We evaluated the ideality factor (n) of the SC via PR spectroscopy, and the results matched theresults of the J-V measurements well. From these results, we demonstrate that the Fj and the n ofthe SCs can be evaluated by using PR spectroscopy.
Mazzucato, E.,Bell, R.E.,Ethier, S.,Hosea, J.C.,Kaye, S.M.,LeBlanc, B.P.,Lee, W.W.,Ryan, P.M.,Smith, D.R.,Wang, W.X.,Wilson, J.R.,Yuh, H. International Atomic Energy Agency 2009 Nuclear fusion Vol.49 No.5
<P>Various theories and numerical simulations support the conjecture that the ubiquitous problem of anomalous electron transport in tokamaks may arise from a short-scale turbulence driven by the electron temperature gradient. To check whether this turbulence is present in plasmas of the National Spherical Torus Experiment, measurements of turbulent fluctuations were performed with coherent scattering of electromagnetic waves. Results from plasmas heated by high harmonic fast waves show the existence of density fluctuations in the range of wave numbers <I>k</I><SUB>⊥</SUB>ρ<SUB>e</SUB> = 0.1–0.4, corresponding to a turbulence scale length of the order of the collisionless skin depth. Experimental observations and agreement with numerical results from the linear gyro-kinetic GS2 code indicate that the observed turbulence is driven by the electron temperature gradient. These turbulent fluctuations were not observed at the location of an internal transport barrier driven by a negative magnetic shear.</P>
Optical and Electrical Properties of InAs/GaAs Quantum-dot Solar Cells
Ryan P. Smith,한임식,김종수,노삼규,임재영 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.6
We investigated the optical and the electrical properties of InAs quantum-dot solar cells (QDSCs)with various InAs deposition thicknesses () via photoluminescence (PL), spectral response (SR),and current density-voltage (J-V) measurements. We fabricated three QDSCs with thicknesses of2.0, 2.5, and 3.0 monolayers (MLs). Our measurements revealed the effects of the QD size onthe spectral response, the conversion efficiency (η) and the device parameters. The QDSCs had amaximum η of 17% for = 2.0 ML under AM1.5G conditions. The change of device parameters invarious QDSCs could be explained by the effects of the balance between enhanced carrier productionfrom the QD layers and carrier trapping/re-capturing by strain-induced defect/QD states.
Temperature Dependence of the Optical Properties of High-density GaAs Quantum Dots
Ryan P. Smith,김종수,이상준,노삼규,김진수,임재영,송진동 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.9
We investigate the effect of the quantum dot (QD) density on the thermal escape and the retrapping processes of carriers for unstrained GaAs/AlGaAs QDs through temperature-dependent photoluminescence measurements. We fabricated high-density GaAs QDs (8.4 ?10<sup>10</sup>/cm<sup>2</sup>, dot-dot distance ∼34 nm) on an Al<sub>0.3</sub>Ga<sub>0.7</sub>As/GaAs (111)A surface by using droplet epitaxy. The average lateral size and height of the GaAs QDs are 24 and 6 nm, respectively. Temperature-dependent photoluminescence (PL) studies show that high-density GaAs QDs undergo a sigmoidal-shape energy shift. The sigmoidal dependence of the PL peak energy can be explained by thermal escaping of carriers followed by re-trapping by QDs. Our analysis indicates that the re-trapping probability of thermally-escaped carriers increases with decreasing dot-to-dot distance (corresponding to an increase in the QD density).
Cytokine profiles in intensive care unit delirium
Ryan J. Smith,Christian Lachner,Vijay P. Singh,Shubham Trivedi,Biswajit Khatua,Rodrigo Cartin-Ceba 대한중환자의학회 2022 Acute and Critical Care Vol.37 No.3
Background: Neuroinflammation causing disruption of the blood-brain barrier and immune cell extravasation into the brain parenchyma may cause delirium; however, knowledge of the exact pathophysiologic mechanism remains incomplete. The purpose of our study was to determine whether cytokine profiles differ depending on whether delirium occurs in the setting of sepsis, coronavirus disease 2019 (COVID-19), or recent surgery.Methods: This prospective observational cohort study involved 119 critically ill patients admitted to a multidisciplinary intensive care unit (ICU) during 2019 and 2020. Delirium was identified using the validated confusion assessment method for the ICU. Multiple delirium risk factors were collected daily including clinical characteristics, hospital course, lab values, vital signs, surgical exposure, drug exposure, and COVID-19 characteristics. Serums samples were collected within 12 hours of ICU admission and cytokine levels were measured.Results: The following proinflammatory cytokines were elevated in our delirium population: tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-18, C-C motif ligand (CCL) 2, CCL3, C-X-C motif chemokine ligand (CXCL)1, CXCL10, IL-8, IL-1 receptor antagonist, and IL-10. Analysis of relative cytokine levels in those patients that developed delirium in the setting of sepsis, COVID-19, and recent surgery showed elevations of CCL2, CXCL10, and TNF-α in both the sepsis and COVID-19 group in comparison to the postsurgical population. In the postsurgical group, granulocyte colony-stimulating factor was elevated and CXCL10 was decreased relative to the opposing groups.Conclusions: We identify several cytokines and precipitating factors known to be associated with delirium. However, our study suggests that the cytokine profile associated with delirium is variable and contingent upon delirium precipitating factors.
Photoreflectance을 이용한 InAs/GaAs 양자점 국소전기장 분포에 관한 연구
한임식,조현준,이상조,손창원,Ryan P. Smith,하재두,박동욱,배인호,김종수,이상준,노삼규 한국물리학회 2012 새물리 Vol.62 No.2
Using photoreflectance spectroscopy(PR), we investigated the optical properties of InAs/GaAs quantum dots (QDs) grown by using molecular beam epitaxy. In the PR spectra of the InAs QD sample, we observed the Franz-Keldysh oscillation (FKO) and determined the localized electric field distribution of the InAs QD sample from the period of the FKO by using the fast Fourier transform (FFT) method. Two components of the FKO frequency due to the heavy-hole and the light-hole transitions existed at a given localized electric field. We suggest that the localized electric fields are strongly correlated to the quantum dot strain field distribution on the GaAs interface. 본 연구에서는 분자선박막성장 장치로 제작된 InAs/GaAs 양자점의 광학적특성을 photoreflectance spectroscopy(PR)를 이용하여 연구하였다. InAs 양자점이 삽입된 시료의 PR 신호에서 시료내부의 전기장에 의한Franz-Keldysh oscillation(FKO)이 관측되었다. 관측된 FKO 신호로부터fast Fourier 변환 (FFT)을 이용하여 InAs 양자점에 의해 형성된국소화된 전기장을 측정하였다. 주어진 전기장에 의해 나타나는 FKO의주파수는 전자-무거운 정공 (e-hh)과 전자-가벼운 정공 (e-lh)간의전이에 의해 두 가지 성분으로 나타난다. 연구결과로부터 InAs 양자점과GaAs 계면에서 양자점에 의한 응력 분포에 의해 국소화된 전기장이형성됨을 제안하였다.