Additional Voltage Drop Research Articles

UV‐Induced Degradation of Industrial PERC, TOPCon, and HJT Solar Cells: The Next Big Reliability Challenge?

With the surge of UV‐transparent module encapsulants in the photovoltaic industry aiming to boost quantum efficiency, modern silicon solar cells must now inherently withstand UV exposure. UV‐induced degradation (UVID) of nonencapsulated laboratory and industrial solar cells from several manufacturers is investigated. Passivated emitter rear contact (PERC), tunnel oxide passivating contact (TOPCon), and silicon heterojunction (HJT) cells can suffer from severe implied voltage degradation (>20 mV) after UV exposure relating to 3.8 years of module installation in the Negev desert. Front UV‐exposure causes more performance loss than an equal rear dose. This is connected to a higher UV transmission of the cell layers outside the bulk, indicating the photons need to reach the silicon surface to induce damage. Current–voltage measurements of the TOPCon groups most sensitive to UV degradation show more than 7%rel efficiency loss with the Voc as the main contributor. For two TOPCon groups, dark storage for 14 days after UV exposure causes an additional voltage drop on a similar scale as the UV damage itself, impeding straightforward reliability testing. UVID appears to be a complex process general to all dominant cell architectures with the potential to diminish efforts in efficiency optimization within only a few years of field employment.

Inductor-Aid Step-Up LLC Resonant Wireless Power Transfer

An inductor-aid step-up LLC wireless power transfer (WPT) system is proposed in this paper. It could step up the WPT output voltage beyond the conventional LLC series-series (SS) compensation method. Employing a parallel inductor with the transmitter coil to lessen the circuit impedance thus the inverter exhibits a new gain curve. The constant frequency operation and simple control of two series active switches in the parallel inductor branch shows a practical improvement of conventional constant frequency LLC WPT system, in terms of voltage demand, new standards and applications. Even the frequency modulation LLC WPT system could be benefited from this enhanced topology rather than to deteriorate the inverter current stress and unnecessary over-rating of magnetic components. The receiver side compensation tank has no additional voltage drop and overcurrent. A 300W prototype has been constructed to validate the concept and performed at 90% efficiency.

Active arc suppression device based on voltage‐source convertor with consideration of line impedance in distribution networks

In the non-effectively grounding distribution system, residual current under single-line-to-ground (SLG) fault threatens the safety of human being and power supply equipment. Active arc suppression device has been proved to be effective for SLG fault arc suppression when the line impedance is ignored. However, in practice, line impedance varies with the fault location and the load current flowing through the impedance brings about additional voltage drop, which increases the fault current and is not dealt with by the conventional methods. To achieve accurate SLG fault arc suppression with the existence of line impedance, the neutral-to-ground voltage reference for full ground-fault current compensation is firstly derived and a detection method is then proposed. The pre-fault and post-fault line currents are used to eliminate the influence of load current on the line impedance voltage drop. A dual-loop voltage and current controller is then designed. The prototype of active arc suppression device was developed. The results of simulation and prototype experiment validate the effectiveness of the proposed method.

Model of the Retrograde Motion of a Vacuum Arc: Comparison to Experiments

In the absence of an external magnetic field, a cathode spot (CS) of a vacuum arc experiences a Brownian random walk (jumps) along the surface. A magnetic field parallel to the surface causes spot drift in the anti-Amperian direction (retrograde motion). Three statements are suggested to explain the retrograde motion and its features: 1) each CS jump is associated with a voltage drop fluctuation $\Delta {V}$ ; 2) the tangential electric field (the Hall field) is created by the additional positive surface charges at the retrograde side of the spot. This field results in an additional voltage drop at the retrograde side of the spot $\delta {V}$ ; and 3) the probability of the spot jumping in the retrograde direction is proportional to $\delta {V} /\Delta {V}$ . Calculations based on these statements allow one to achieve qualitative and, in many cases, quantitative agreement with experiments concerning retrograde velocity dependences on these external parameters: magnetic field, arc current, interelectrode gap, and cathode surface conditions. No adjustable parameters were used in these calculations.

전기적 부하 시험 장치를 위한 데드타임 및 유도성 전압강하 보상 기법이 적용된 가상자속 추정 기법에 관한 연구

This paper presents improved SOGI-FLL method to test the load of electric test equipment composed of two inverters. The simulator makes variable magnitudes and frequency of the voltage and EUT have output voltage sensor-less function for synchronous of simulator voltage by SOGI-FLL. The proposed SOGI-FLL have an additional reactance voltage drop compensation and dead-time compensation. The EUT has harmonics of the voltage generated in the current flowing through the filter due to the dead time. When the output voltage of the EUT(Equipment Under Test), which is a signal input to the SOGI filter, is very small and is distorted, the frequency estimation characteristic is degraded. To improve this, the dead time voltage is compensated for the command voltage depending on the output current direction of the test equipment. In addition, when the output voltage of the simulator is small and large current flows to the EUT, the SOGI input signal becomes small, which causes problems in frequency estimation. Thereby improving the frequency estimation characteristic by compensating the voltage drop of the filter. Electrical test equipment simulating motor load has variable voltage, frequency and current. The proposed method was simulated and tested to improve the properties of SOGI-FLL for electrical load testing.

Current–voltage characteristics of InGaN/GaN blue light-emitting diodes investigated by photovoltaic parameters

We investigate the current–voltage (I–V) characteristics of InGaN/GaN multiple-quantum-well blue light-emitting diodes (LEDs) to analyze the additional voltage drop outside the active region. We theoretically examine and measure the short-circuit current versus the open-circuit voltage (ISC–VOC) obtained by photoexcitation and compare them with the I–V obtained by electrical injection. The ISC–VOC curve shows the ideal I–V characteristics that do not contain the deviation from the exponential behavior. In the ideality factor obtained by differentiating the ISC–VOC curve, the increase of ideality factor due to the series resistance is not observed. The slope of the additional voltage drop ΔV versus current curve shows a nonlinear behavior, indicating that a simple ohmic voltage drop is not sufficient to explain ΔV. From these observations, it is concluded that the carrier recombination in the active region plays a non-negligible role in I–V characteristics of LEDs deviating from the ideal behavior.

3D‐Printed Electrodes with Improved Mass Transport Properties

AbstractToday's electrochemical reactor design is a less developed discipline as compared to electrocatalytic synthesis. Although catalysts show increasing conversion rates, they are often operated without measures for the reduction of concentration polarization effects. As a result, a stagnant boundary layer forms at the electrode‐electrolyte interface. This stagnant boundary layer presents an additional voltage drop and reduces the energy efficiency. It is generally accepted that this phenomenon is caused by a combination of fast electrode reactions and slow diffusion of the reacting species. Our earlier work demonstrated the potential of non‐conducting static mixers to reduce concentration polarization effects. However, there are few studies on conductive static mixers applied as electrodes. In this study, we present a new concept of additive manufactured flow through electrode mixers. Our electrode geometry combines a high surface area with mixing properties, diminishing concentration polarization effects of transport‐limited reactions. Mass transport properties of these conductive static mixers are evaluated in an additive manufactured electrochemical reactor under controlled conditions by applying the limiting‐current method.

Comprehensive Writing Margin Analysis and its Application to Stacked one Diode‐One Memory Device for High‐Density Crossbar Resistance Switching Random Access Memory

The sneak current through the neighboring cells interrupts reading of a selected cell in high‐resistance state in crossbar resistance switching random access memory (RRAM). As the sneak current mainly originates from a parallel resistance component to a selected cell, write operation, which requires sufficiently high voltage delivered to the selected cell, has been regarded to have little relevance to the sneak current issue. In this work, it is revealed that an additional voltage drop on the wire resistances of selected word and bit lines causes an increase in voltage for the write operation (programming/erasing), whose degree is associated with the selectivity of the RRAM selector, array size, resistance of the selected cell, and wire resistances. The presence of sneak paths gives rise to an additional concern about the disturbance of the unselected cells, especially when the writing voltage of the selected cell was increased by the aforementioned factors. A floating voltage scheme is considered for proposing a unified writing margin analysis model with diode selectors, and a feasible design strategy based on the analysis for an experimental RRAM device employing a diode with an extremely high rectification ratio (8.4 × 108) is provided. Furthermore, application of the model to the universal RRAM devices, irrespective of their switching polarity, selector types, and adopted voltage schemes, is included.

The Effect of Surface Functionalization on the Electrochemical Lithiation of Silicon for Li Ion Batteries

Lithium-ion batteries are widely used in consumer electronics and are commercially available for transportation applications. However, the limited energy capacities of current electrode materials mean that widespread applications in transportation are potentially limited. Therefore, there are substantial research efforts on new materials with higher capacities than those of current electrode materials. Among them, silicon has attracted widespread attention as an alternative anode material to graphite due to its large gravimetric and volumetric capacities. The lithiation of crystalline Si, however, results in significant structural changes as compared to transition metal oxides or graphitic material. The large volume expansion increases the interaction with electrolyte leading to detrimental effects on the capacity. Si atom has four valence electrons, requiring four bonds to saturate its valence shell. In the presence of H and O in the vicinity of Si surface, surface Si atoms are saturated with these passivating agents. It is therefore often observed that Si surfaces are hydrogenated or oxidized. It has also been suggested that Mn can be present on the anode, coming from dissolution of cathode materials such as lithium manganese oxide. Given these considerations, the motivations of this study are thus twofold. The first such motivation is to build an atomistic-level understanding of the effects of the realistic surface terminations on the lithiation process. This analysis complements and extends previous work on the lithiation of clean Si surfaces.1 The second motivation is that, because of the generally recognized importance of SEI layer, which forms on the electrode surface as a result of decomposition of thermodynamically unstable electrolyte molecules, we develop strategies to predict which types of functionalized surfaces may impact SEI formation. Thus, we studied here how the functionalization impacts the lithiation process itself. In this talk, we will present the results of an extensive computational study for the lithiation of functionalized Si surfaces. First principles calculations, with a history-dependent lithium insertion algorithm, are used to model the mechanism of lithiation of the functionalized crystalline Si. The lithiated configurations for the Mn/Si(100), (110), and (111) surfaces at different lithiation stages show the progression of amorphous crystalline boundary with increasing Li content. For all surfaces, we find that Si is amorphized by breakdown of Si-Si chains upon Li insertion. For Mn/Si(111), the sheets of connected Si atoms are formed and maintained up to the highest Li content. At high Li concentration (x>3), some isolated Si atoms are formed, in particular for Mn/Si(110) and Mn/Si(111) surfaces. For all surfaces, Mn is found trapped below the surface, underneath the Si dimers. The analysis of the voltage curves reveals both similar and different characteristics with those of the clean Si surfaces. (110) surface has the highest voltage plateau as compared to other surfaces. We also find the maximum Li that can be inserted to vary from one surface to another, and the trends differ from those of the clean Si surfaces. For hydroxilated Si surface, on the other hand, we find the lithiated configurations resemble to those of clean Si surfaces; formation of Si dimers are observed as well as few isolated Si atoms at high Li content. The voltage plot suggests an additional voltage drop at low Li content originating from the presence of OH/H species on the surface, and a slight reduction in the maximum Li that can be inserted as compared to the clean Si surfaces. The atomistic and electronic structure origins of the differences will be discussed. [1] M. K. Y. Chan, C. Wolverton, and J. Greeley, Journal of the American Chemical Society 134 (2012) 14362

P-type Doping of Organic Charge Transport Materials with Tungsten Oxide

ABSTRACTThe effects of WO3 doping in 4,4’-bis-9-carbozyl biphenyl (CBP) were studied through detailed electrical device characterization. A series of hole-only devices have been fabricated, where the doping level was varied from 10-40mol% and the doped CBP thickness was varied from 5-40 nm. It was found that, to achieve effective doping for improved hole injection and transport, the doping level should be greater than 20mol% and the doped layer should be at least 10 nm thick. It was also found that an energy barrier exists at the doped and undoped CBP interface, resulting in an additional voltage drop. This finding was explained by a large downward shift of the Fermi level in WO3-doped CBP, which causes band bending and depletion at the interface. Finally, simplified green phosphorescent organic light-emitting diodes (OLEDs) with CBP as the hole transport and host material were fabricated. With a WO3-doped hole transport layer, the OLEDs attained brightness above 105 cd/m2 at 20 mA/cm2, and exhibited an improved reliability under constant-current stressing as compared to undoped OLEDs.

Saturation Current and On-Resistance Correlation during During Repetitive Short-Circuit Conditions on SiC JFET Transistors

This letter presents a correlation between the reduction of the saturation current level and increase of on-state resistance and the top-metal ageing of normally ON SiC junction gate field effecttransistors. For this study, ageing has been obtained using repetitive short-circuit operations. Among monitored parameters during ageing, on-state resistance and short-circuit current level are those, which have the strongest evolution. The top-metal degradation has been characterized via the on-state resistance measurement during ageing. In particular, we clearly show that the top-metal restructuration due to ageing leads to an additional voltage drop between gate and source terminals and results to a lower gate-source junction voltage.

The Fabrication Study of Branched Cathode Electrode for Field Emitter in a FED Panel

Using carbon nanotubes as field emitters, the field emission display panel with branched cathode electrode was fabricated. For the cathode faceplate, the branched cathode electrode was composed of the emitter conducting layer and the emitter supporting layer. On the emitter supporting layer surface the carbon nanotubes field emitters were prepared, and the emitter conducting layer would be covered with the emitter insulation layer. The applied cathode potential would be conducted by the emitter conducting layer, which could decrease the additional voltage drop. The good field emission characteristic for the fabricated field emission display panel was confirmed.

Electron Tunneling Spectroscopy of SmB<SUB>6</SUB> Studied by <I>In Situ</I> Nano-Break-Junction Method

Tunneling spectra of intermediate-valence semiconductor SmB6 are reported for in-situ break junctions, being able to make nano-scale planar tunnel junctions. The electron tunneling using break junction method is a powerful probe of the intrinsic energy gap. The investigated tunneling conductance dI/dV curves are mostly reproducible and symmetric with respect to the applied voltage. Two kinds of characteristic energy gaps are observed at 2E(d) = 20 mV and 2E(a) = 9 mV, which coincides well with those previously studied by point-contact spectroscopy and the activation energy fitted by our electrical resistivity data. The positions of the gap structures are independent of the zero-bias conductance, implying no additional voltage drop induced by the break junctions. The small anomaly at the activation energy 2E(a) indicates a relatively low density of in-gap states. Furthermore, the results of magnetic properties reveal the ratio of Sm2+:Sm3+ = 3.7:6.3 and the antiferromagnetic nature at high temperature.

Analysis and Minimization of Ligand Concentration Errors at the Internal Face of Excised Patches

Confocal patch-clamp fluorometry is a method combining patch-clamp techniques and confocal fluorescence microscopy for simultaneous investigation of channel activation and ligand binding in ion channels, as used for CNGA2 olfactory channels and HCN2 pacemaker channels. The fluorescent ligands fcAMP and fcGMP, and the reference DY647, used in these studies were negatively charged. Their fluorescence signals in the volume between patch membrane and pipette tip can depend significantly on the applied voltage if the conditions are not optimized, indicating a difference between actual ligand concentration at the patch and in the bath.Using confocal PCF and fluorescence correlation spectroscopy, we analyzed this phenomenon and looked for conditions to overcome this problem. (1) When investigating not or only slightly voltage dependent ion channels, we propose to use low voltages. (2) When investigating ion channels with a high single channel conductance, causing macroscopic ion currents in the range of tens of nA, we propose a reduced expression to keep the membrane resistance reasonably high. (3) For all ion channel types we recommend the use of pipette tips with a planar surface following the fabrication protocol of Hilgemann (1995). These pipette shapes avoid any significant additional voltage drop across the pipette tip and thus also the described errors of the charged molecules.We compare the activation and binding behaviour of CNG channels, having a minor voltage dependence and a high single channel conductance, with closely related HCN channels, having a pronounced voltage dependence and a low single channel conductance. It is concluded that in excised macropatches with large currents the concentration of charged molecules at the internal face of the patch can significantly deviate from that in the bath solution and that appropriate experimental conditions can largely avoid the problem.

Numerical analysis of gas crossover effects in polymer electrolyte fuel cells (PEFCs)

The gas crossover phenomenon in polymer electrolyte fuel cells (PEFCs) is an indicator of membrane degradation. The objective of this paper is to numerically investigate the effects of hydrogen and oxygen crossover through the membrane in PEFCs. A gas crossover model is newly developed and implemented in a comprehensive multi-dimensional, multi-phase PEFC model developed earlier. A parametric study is carried out to investigate the effects of the crossover diffusion coefficients for hydrogen and oxygen as well as the membrane thickness. The simulation results demonstrate that the hydrogen crossover induces an additional oxygen reduction reaction (ORR) and consequently causes an additional voltage drop, while the influence of oxygen crossover on PEFC performance is relatively insignificant because it leads to the hydrogen/oxygen chemical reaction at the anode side. Finally, using the time-dependent gas crossover data that are available in the literature (measured in days), we conduct gas crossover simulations to examine the effects of increased gas crossover due to membrane degradation on PEFC performance and successfully demonstrate decaying polarization curves with respect to time. This study clearly elucidates the detailed mechanisms of the hydrogen and oxygen crossover phenomena and their effect on PEFC performance and durability.

The origin of dispersion of magnetoresistance of a domain wall spin valve

We theoretically study the current-perpendicular-to-plane magnetoresistance of a domain wall confined in a nanocontact which is experimentally fabricated as current-confined-path (CCP) structure in a nano-oxide-layer (NOL). We solve the non-collinear spin diffusion equation by using the finite element method and calculate the MR ratio by evaluating the additional voltage drop due to the spin accumulation. We investigate the origin of dispersion of magnetoresistance by considering the effect of randomness of the size and distribution of the nanocontacts in the NOL. It is observed that the effect of randomness of the contact size is much larger than that of the contact distribution. Our results suggest that the origin of dispersion of magnetoresistance observed in the experiments is the randomness of the size of the nanocontacts in the NOL.

Voltage drop in an (AlxGa1−x)0.5In0.5P light-emitting diode probed by Kelvin probe force microscopy

The authors report on quantitative investigations of the voltage drop across the heterostructure layer sequence of an operating AlGaInP light-emitting diode via Kelvin probe force microscopy for different external biases between −2.0 and +1.86V. In the low voltage regime, most of the voltage drops in the active layer. For bias voltages above +1.5V, however, they found an additional voltage drop on the p side of the device, which reduces the power efficiency of the light-emitting diode.

Electrical Detection of Spin Accumulation at a Ferromagnet-Semiconductor Interface

We show that the accumulation of spin-polarized electrons at a forward-biased Schottky tunnel barrier between Fe and -GaAs can be detected electrically. The spin accumulation leads to an additional voltage drop across the barrier that is suppressed by a small transverse magnetic field, which depolarizes the spins in the semiconductor. The dependence of the electrical accumulation signal on magnetic field, bias current, and temperature is in good agreement with the predictions of a drift-diffusion model for spin-polarized transport.

Band-edge aligned quaternary carrier barriers in InGaAs-AlGaAs high-power diode lasers for improved high-temperature operation

A new type of band-edge aligned carrier barrier is introduced into InGaAs-AlGaAs single quantum-well (SQW) high-power diode laser structures in order to prevent thermionic emission and the overflow of carriers at elevated operating temperatures. These barriers, which are located in the direct vicinity of the active zone of the laser, are undoped to avoid free-carrier absorption. An InGaAs-AlGaAs SQW laser structure with a 10-nm-thick AlGaAsSb electron-blocking layer on the p-side of an In/sub 0.2/Ga/sub 0.8/As quantum well was realized. The composition of this layer was adjusted so that its valence-band edge matches that of the adjacent AlGaAs waveguide layer. This is to prevent any additional voltage drop or series resistance due to the injection of holes into the quantum well through the electron blocking layer. These lasers show a high characteristic temperature T/sub 0/ of about 225 K for 1500-/spl mu/m-long as-cleaved devices, which is about 60 K higher than the same laser structure without the blocking layer. Simultaneously low internal losses (/spl alpha//sub i//spl ap/1.5 cm/sup -1/ at 20/spl deg/C) and high internal quantum efficiencies (/spl eta//sub i//spl ap/93% at 20/spl deg/C) are achieved. No additional voltage drop or series resistance was measured. The higher temperature stability is mainly attributed to the suppression of carrier leakage and a reduced free-carrier absorption at elevated temperatures.

Spatially resolved detection of phase locking in Josephson junction arrays

Abstract Two-dimensional arrays of shunted Nb/AlOx/Nb Josephson junctions have been investigated. Shapiro steps in the current–voltage ( I – V ) curve of an on-chip detector junction can be used to sense mutual phase locking of the array junctions. By scanning the array with a low-power electron beam, the phase locked junctions remain locked, whereas the unlocked junctions generate a beam-induced additional voltage drop along the array. In regions of the array’s bias current where pronounced Shapiro steps occur in the detector’s I – V curve, practically no array junction generates a beam-induced voltage signal, thus indicating complete mutual locking. For other bias currents of the array with less than maximum detected power, some of the junctions generate beam-induced signals, and can be identified as being non-locked. Our investigations allow a detailed and spatially resolved analysis of mutual phase locking in arrays of Josephson junctions. Moreover, the results obtained with autonomous arrays are compared to experiments performed with injection locked arrays.