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RISS 인기검색어
- 검색키워드
- 저자 : Garcia-Belmonte, Germà (검색결과 4 건)
- 무료
- 기관 내 무료
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Perimeter leakage current in polymer light emitting diodes
Germà Garcia-Belmonte,José M. Montero,Yassid Ayyad-Limonge,Eva M. Barea,Juan Bisquert,Henk J. Bolink 한국물리학회 2009 Current Applied Physics Vol.9 No.3
Observation of leakage current paths through the device perimeter in standard poly(phenylene vinylene)-based light-emitting devices is reported. Perimeter leakage currents govern the diode performance in reverse and low positive bias and exhibit an ohmic character. Current density correlates with the perimeter-to-area ratio thus indicating that leakage currents are mainly confined on polymer regions in the vicinity of metallic contact limits (device perimeter). Observation of leakage current paths through the device perimeter in standard poly(phenylene vinylene)-based light-emitting devices is reported. Perimeter leakage currents govern the diode performance in reverse and low positive bias and exhibit an ohmic character. Current density correlates with the perimeter-to-area ratio thus indicating that leakage currents are mainly confined on polymer regions in the vicinity of metallic contact limits (device perimeter).
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Guerrero, Antonio,Garcia-Belmonte, Germà,Mora-Sero, Ivan,Bisquert, Juan,Kang, Yong Soo,Jacobsson, T. Jesper,Correa-Baena, Juan-Pablo,Hagfeldt, Anders American Chemical Society 2016 The Journal of Physical Chemistry Part C Vol.120 No.15
<P>Impedance spectroscopy offers access to all the different electronic and ionic processes taking place simultaneously in an operating solar cell. To date, its use on perovskite solar cells has been challenging because of the richness of the physical processes occurring within similar time domains. The aim of this work is to understand the general impedance response and propose a general equivalent circuit model that accounts for the different processes and gives access to quantitative analysis. When the electron-selective contacts and the thickness of the perovskite film are systematically modified, it is possible to distinguish between the characteristic impedance signals of the perovskite layer and those arising from the contacts. The study is carried out using mixed organic lead halogen perovskite (FA(0.85)MA(0.15)Pb(I0.85Br0.15)(3)) solar cells with three different electron-selective contacts: SnO2, TiO2, and Nb2O5. The contacts have been deposited by atomic layer deposition (ALD), which provides pinhole-free films and excellent thickness control in the absence of a mesoporous layer to simplify the impedance analysis. It was found that the interfacial impedance has a rich structure that reveals different capacitive processes, serial steps for electron extraction, and a prominent inductive loop related to negative capacitance at intermediate frequencies. Overall, the present report provides insights into the impedance response of perovskite solar cells which enable an understanding of the different electronic and ionic processes taking place during device operation.</P>
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Germanium coating boosts lithium uptake in Si nanotube battery anodes
Haro, Marta,Song, Taeseup,Guerrero, Antonio,Bertoluzzi, Luca,Bisquert, Juan,Paik, Ungyu,Garcia-Belmonte, Germà The Royal Society of Chemistry 2014 Physical chemistry chemical physics Vol.16 No.33
<P>Si nanotubes for reversible alloying reaction with lithium are able to accommodate large volume changes and offer improved cycle retention and reliable response when incorporated into battery anodes. However, Si nanotube electrodes exhibit poor rate capability because of their inherently low electron conductivity and Li ion diffusivity. Si/Ge double-layered nanotube electrodes show promise to improve structural stability and electrochemical kinetics, as compared to homogeneous Si nanotube arrays. The mechanism explaining the enhancement in the rate capabilities is revealed here by means of electrochemical impedance methods. The Ge shell efficiently provides electrons to the active materials, which increase the semiconductor conductivity thereby assisting Li<SUP>+</SUP> ion incorporation. The charge transfer resistance which accounts for the interfacial Li<SUP>+</SUP> ion intake from the electrolyte is reduced by two orders of magnitude, indicating the key role of the Ge layer as an electron supplier. Other resistive processes hindering the electrode charge–discharge process are observed to show comparable values for Si and Si/Ge array electrodes.</P> <P>Graphic Abstract</P><P>Interfacial charge transfer resistance accounting for Li intake extremely reduced by conductive germanium coating of Si nanotubes. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4cp02377c'> </P>
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Park, Kang-Joon,Lim, Byung-Beom,Choi, Moon-Ho,Jung, Hun-Gi,Sun, Yang-Kook,Haro, Marta,Vicente, Nuria,Bisquert, Juan,Garcia-Belmonte, Germà The Royal Society of Chemistry 2015 Journal of Materials Chemistry A Vol.3 No.44
<P>To increase the reversible capacity of layered lithium nickel-cobalt-manganese oxide, a Li[Ni0.8Co0.06Mn0.14]O2positive electrode with a two-sloped full concentration gradient (TSFCG) was successfully synthesized<I>via</I>co-precipitation. The TSFCG maximizes the Ni concentration in the particle core and the Mn concentration on the particle surface. The TSFCG Li[Ni0.8Co0.06Mn0.14]O2positive electrode showed improved overall electrochemical properties (<I>i.e.</I>, reversible capacity, cycle life, and rate capability) and thermal stability compared to a conventional positive electrode (CC) Li[Ni0.8Co0.06Mn0.14]O2without a concentration gradient. Electrochemical impedance spectroscopy showed that the high stability of the outer surface composition of Li[Ni0.64Co0.06Mn0.30]O2is responsible for reduction in surface resistance and charge transfer resistance by decreasing the parasitic reaction with the electrolyte. These reduced resistances explain the superior rate capability of TSFCG positive electrodes.</P>
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