Equivalent series resistance

About: Equivalent series resistance is a research topic. Over the lifetime, 5335 publications have been published within this topic receiving 83362 citations. The topic is also known as: ESR.

Architectural Modifications for Flexible Supercapacitor Performance Optimization

Abstract: We have developed material and architectural alternatives for flexible supercapacitors and investigated their effect on practical performance. The substrate alternatives include paperboard as well as various polyethylene terephthalate (PET) films and laminates, with aqueous NaCl electrolyte used in all devices. In all the supercapacitors, activated carbon is used as the active layer and graphite ink as the current collector, with various aluminium or copper structures applied to enhance the current collectors’ conductivity. The capacitance of the supercapacitors was between 0.05 F and 0.58 F and their equivalent series resistance (ESR) was from <1 Ω to 14 Ω, depending mainly on the current collector structure. Furthermore, leakage current and selfdischarge rates were defined and compared for the various architectures. The barrier properties of the supercapacitor encapsulation have a clear correlation with leakage current, as was clearly shown by the lower leakage in devices with an aluminium barrier layer. A cycle life test showed that after 40000 charge-discharge cycles the capacitance decreases by less than 10%.

Multiple function type D/A converter

Abstract: A multiple function type D/A converter utilizing a ladder type resistance circuit, and capable of other mathematical functions in addition to the D/A conversion, having a series resistance circuit consisting of N number of resistors R2 1 ˜R2 n each having a resistance value R connected in series between an output terminal V o and one side of a terminal resistor R o which has a resistance value 2R and is connected on its other side to ground, such series circuit including a resistor connecting point between each adjacent pair of resistors R 0 , R2 1 ˜R2 N , and branching in parallel therefrom N+1 number of groups of parallel resistors 01˜0n, 11˜1n, . . . N1˜Nn, each containing n resistors where n is an integer greater than 1, the n resistors of each such group being all connected on one side to the same resistor connecting point with different groups thereof connected to different connecting points along such series circuit, the n resistors of each such group being individually switchable on the other side thereof alternately between ground and a reference voltage V s by means of corresponding groups of switching circuits S 01 ˜S 0n . . . S N1 ˜S Nn under the control of applied digital signals.

Consideration of the Actual Current-Spreading Length of GaN-Based Light-Emitting Diodes for High-Efficiency Design

Abstract: Based on the proposed experimental method, the current spreading length of GaN-based light-emitting diodes (LEDs) was measured and analyzed for practical device design. In this study, Thompson's and Guo's models, which are categorized according to vertical series resistance (in particular, p-type contact resistance), were used to extract device parameters. It was shown that the measured current spreading length strongly depends on the injected current density. For LEDs fabricated with low-resistance p-type contacts, this behavior could be explained in terms of the accelerated current crowding with higher current densities occurring as a result of the reduced voltage drop across the junction, which is in good agreement with Thompson's relation. However, for LEDs fabricated with high-resistance p-contacts, unlike Guo's prediction, the measured current spreading length also showed a strong dependence on the injected current density. This was attributed to thermal heating at the p-contact, resulting in the reduction of the voltage drop across the p-contact and so junction voltage, which is also in agreement with Thompson's model. Based on the measured parameters and the design rule, efficient p-type reflectors, namely, hybrid reflectors were designed. Compared with conventional ones, LEDs fabricated with the hybrid reflectors exhibited better output power at a reasonable forward voltage, indicating that the proposed method is effective in understanding the actual current spreading and hence the practical design of high-efficiency LEDs.

InGaAs axial-junction nanowire-array solar cells

Abstract: Axial p–i–n junction nanowire (NW) solar cells (SCs) with a position-controlled GaAs-based NW array were fabricated by selective-area metal organic vapor phase epitaxy (SA-MOVPE). The measured electron-beam-induced current (EBIC) signals showed the formation of an axial p–i–n junction, which confirms power generation under sunlight illumination. The series resistance of the NW SCs is much higher than that of conventional planar SCs based on Si or other III–V compound semiconductors. The main difficulty concerning the fabrication of these NW SCs is the degradation of series resistance between the GaAs-based NWs and the indium–tin oxide (ITO) deposited as a transparent electrode. The series resistance of the fabricated GaAs-based NW SCs was reduced by introducing a tin doping contact layer between the ITO and the NW array, which is formed by pulse doping. As a result of this improved structure, the fabricated SCs exhibited an open-circuit voltage of 0.544 V, a short-circuit current of 18.2 mA/cm2, and a fill factor of 0.721 for an overall conversion efficiency of 7.14% under AM1.5G illumination. The series resistance of the SCs could be decreased to 0.132 Ωcm2, which is one order of magnitude lower than that of the SC without a highly doped contact layer. This reduced series resistance indicates that nanostructure SCs with transparent electrodes and multijunction NW SCs with high efficiencies can be fabricated on a commercial basis in the near future.