Home About us Contact
|
Home About us Contact | ||
|
|
||
Diode Characteristics (diode + characteristic)
Selected AbstractsSHORT COMMUNICATION: ACCELERATED PUBLICATION: Diode characteristics in state-of-the-art ZnO/CdS/Cu(In1,xGax)Se2 solar cells,PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 3 2005Miguel A. Contreras Abstract We report a new state of the art in thin-film polycrystalline Cu(In,Ga)Se2 -based solar cells with the attainment of energy conversion efficiencies of 19·5%. An analysis of the performance of Cu(In,Ga)Se2 solar cells in terms of some absorber properties and other derived diode parameters is presented. The analysis reveals that the highest-performance cells can be associated with absorber bandgap values of ,1·14,eV, resulting in devices with the lowest values of diode saturation current density (,3×10,8,mA/cm2) and diode quality factors in the range 1·30,<,A,<,1·35. The data presented also support arguments of a reduced space charge region recombination as the reason for the improvement in the performance of such devices. In addition, a discussion is presented regarding the dependence of performance on energy bandgap, with an emphasis on wide-bandgap Cu(In,Ga)Se2 materials and views toward improving efficiency to >,1;20% in thin-film polycrystalline Cu(In,Ga)Se2 solar cells. Published in 2005 John Wiley & Sons, Ltd. [source] ta-C/Si heterojunction diodes with apparently giant ideality factorsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2010Marc Brötzmann Abstract A common feature of many wide band gap heterojunction diodes is an unexplained large ideality factor n > 2. In this context we investigate the diode characteristics of heterojunction diodes consisting of a crystalline semiconductor material such as Si covered with a thin semiconducting film of amorphous or disordered material. As thin amorphous film we use tetrahedral amorphous carbon (ta-C). These heterojunctions exhibit a pronounced rectifying behavior, low saturation current and low parasitic currents. Moreover, we observe an apparently giant ideality factor reaching values of n > 75. As a consequence, the turn on voltage is around 3 , 10 V and the I-V curves can be measured for bias up to 40 V without reaching saturation or electrical breakdown. We present a quantitative model for the unusual diode characteristics of these Metal , Amorphous Semiconductor , Semiconductor diodes (MASS-diodes). We demonstrate that the I-V characteristics of the heterojunctions are well described by a serial arrangement of an ideal Schottky-diode, a Frenkel-Poole type resistance and an Ohmic contact resistance, emulating a p-n- or Schottky diode characteristic with giant ideality factor and referred to as the FPID-model. We propose that heterojunctions exhibiting apparently large ideality factors n , 2 may possess an interfacial disordered or amorphous layer with Frenkel-Poole conduction properties. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Alkyl-Chain-Length-Independent Hole Mobility via Morphological Control with Poly(3-alkylthiophene) NanofibersADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Wibren D. Oosterbaan Abstract The field-effect transistor (FET) and diode characteristics of poly(3-alkylthiophene) (P3AT) nanofiber layers deposited from nanofiber dispersions are presented and compared with those of layers deposited from molecularly dissolved polymer solutions in chlorobenzene. The P3AT n -alkyl-side-chain length was varied from 4 to 9 carbon atoms. The hole mobilities are correlated with the interface and bulk morphology of the layers as determined by UV,vis spectroscopy, transmission electron microscopy (TEM) with selected area electron diffraction (SAED), atomic force microscopy (AFM), and polarized carbon K -edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The latter technique reveals the average polymer orientation in the accumulation region of the FET at the interface with the SiO2 gate dielectric. The previously observed alkyl-chain-length-dependence of the FET mobility in P3AT films results from differences in molecular ordering and orientation at the dielectric/semiconductor interface, and it is concluded that side-chain length does not determine the intrinsic mobility of P3ATs, but rather the alkyl chain length of P3ATs influences FET diode mobility only through changes in interfacial bulk ordering in solution processed films. [source] Photogalvanic effect in aqueous Methylene blue nickel mesh systems: Conversion of light into electricityINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2001Ilker S. Bayer Abstract The photogalvanic effect in electrochemical cells, employing aqueous Methylene blue and Fe(II)/Fe(III) couple electrolyte and nickel-mesh electrodes, were experimentally investigated. Five different standard H-cell configurations were set-up by modifying the electrolyte. Long-term open-circuit voltage measurements were conducted in order to test the stability of the cells. Light on,off reproducibility experiments were also carried out during lengthy cell operations. By comparing experimental quantum yield with theoretical predictions, it was found that the cells operate on differential electrode kinetics. Oxidation of the illuminated electrode was detected. This affected the current,voltage characteristics of the cells after a sufficiently long cell operation. Schottky junction treatment was used to model the electrolyte,electrode junction. After calculating the ratio between the majority carrier (electron) current density and minority carrier (hole) current density, we concluded that the oxidation of the electrodes contributes positively to the cell performance since the electrode,electrolyte interface shows unipolar Schottky diode characteristics. Copyright © 2001 John Wiley & Sons, Ltd. [source] A low local oscillator power K-band mixer based on tunneling diodesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2009Iacopo Magrini Abstract In this article, we will demonstrate a low local oscillator (LO) power K-band mixer based on a tunneling diode technology. Due to its unique diode characteristics, no DC supply is needed, whereas an LO power as low as ,2 dBm is required for nominal functionality. The energy-efficient MMIC prototype integrates a pair of heterojunction interband tunnel diodes and a 90° coplanar broadband coupler. The prototype is optimized within the 19,26 GHz band, with an IF ranging from zero to 7 GHz. In addition, when compared with other mixers, it has the lowest LO power requirement with a conversion loss ranging from 6 to 10 dB, an input compression point of ,3 dBm and an intercept 2nd and 3rd order intermodulation point of 22 and 12 dBm, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1140,1143, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24228 [source] Open-circuit voltage increase dynamics in high and low deposition rate polymorphous silicon solar cellsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2010E. V. Johnson Abstract The dynamics of the open-circuit voltage (VOC) of polymorphous silicon (pm-Si:H) solar cells deposited at high and low rates (8 and 1.5,Ĺ/s, HR and LR) and containing lightly or heavily doped p-layers (LD or HD) are compared through in situ, variable intensity measurements during light-soaking (LS). The VOC's of the LR cells show an increase with LS, regardless of doping level, whereas the HR cells show decreasing VOC's. This result is in contrast to the changes predicted by the dark diode characteristics, which predict increasing VOC for all the devices. The device measurements are compared to the analogous measurements on co-deposited coplanar p,i layer stacks to determine whether the VOC dynamics can be linked to changes in the p-layer doping efficiency during LS. The changes to the macroscopic electrical behaviour of the cell under varying light conditions are modelled using a simple, three parameter function, and are compared to results from a detailed, numerical modelling tool, AFORS-HET. [source] ta-C/Si heterojunction diodes with apparently giant ideality factorsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2010Marc Brötzmann Abstract A common feature of many wide band gap heterojunction diodes is an unexplained large ideality factor n > 2. In this context we investigate the diode characteristics of heterojunction diodes consisting of a crystalline semiconductor material such as Si covered with a thin semiconducting film of amorphous or disordered material. As thin amorphous film we use tetrahedral amorphous carbon (ta-C). These heterojunctions exhibit a pronounced rectifying behavior, low saturation current and low parasitic currents. Moreover, we observe an apparently giant ideality factor reaching values of n > 75. As a consequence, the turn on voltage is around 3 , 10 V and the I-V curves can be measured for bias up to 40 V without reaching saturation or electrical breakdown. We present a quantitative model for the unusual diode characteristics of these Metal , Amorphous Semiconductor , Semiconductor diodes (MASS-diodes). We demonstrate that the I-V characteristics of the heterojunctions are well described by a serial arrangement of an ideal Schottky-diode, a Frenkel-Poole type resistance and an Ohmic contact resistance, emulating a p-n- or Schottky diode characteristic with giant ideality factor and referred to as the FPID-model. We propose that heterojunctions exhibiting apparently large ideality factors n , 2 may possess an interfacial disordered or amorphous layer with Frenkel-Poole conduction properties. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Processing approaches of AlGaN/GaN Metal Insulator Semiconductor Hetero Field Effect Transistors (MISHFET) on Si (111) substratesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009Martin Eickelkamp Abstract We report on the fabrication of AlGaN/GaN MISHFETs using SiO2 and SiN as gate dielectrics. In particular, two different passivation procedures are investigated with respect to the resulting electrical properties. A fluorine based ICP etch step, as used here to remove the gate dielectric prior to passivation layer deposition, is shown to deteriorate the sheet carrier concentration and mobility. Depositing the passivation layer upon the gate dielectric, on the other hand, slightly decreases the sheet resistance as compared to a conventional HFET. Gate diode characteristics reveal significant reduction of gate leakage currents in both, reverse and forward biasing regions, of 1-2 and up to 6 orders of magnitude, respectively. All devices exhibit more pronounced current collapse compared to a conventional passivated HFET. In addition, a clear depencency on the processing scheme is observed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||