Decrease In Series Resistance Research Articles

N-Doping of thermally polymerizable fullerenes as an electron transporting layer for inverted polymer solar cells

A novel [6,6]-phenyl-C61-butyric acid methyl styryl ester (PCBM-S) was synthesized and employed as an electron transporting interfacial layer for bulk heterojunction polymer solar cells with an inverted device configuration. After the deposition of PCBM-S film from solution, the styryl groups of PCBM-S were polymerized by post-thermal treatment to form a robust film which is resistive to common organic solvents. This allows the solution processing of upper bulk heterojunction film without eroding the PCBM-S layer. Additionally, the PCBM-S was n-doped with decamethylcobaltocene (DMC) to increase the conductivity of the film, which resulted in a significantly improved power conversion efficiency from 1.24% to 2.33%. The improved device performance is due to the decrease of series resistance and improved electron extraction property of the n-doped PCBM-S film.

Investigation on photocurrent of ZnPc/C60 solar cells

Solar cells with structure of ZnPc (20 nm)/C60 (10 nm) are fabricated by thermal evaporation. The photocurrent density (Jph) expressed by effective applied voltage (V0-Va) and light intensity (I) is derived from an analytical method, and it is shown that the results from the model are in good agreement with experimental results. The short-circuit current density (JSC) exhibits a nearly linear dependence on light intensity, which is partially determined by effective applied voltage. Thermal annealing treatment under an optimal condition of 100 ℃ and 20 min, improves JSC by 43.8%, lengthening its attenuation constant from 5.6h to 22.2 h, which is attributed to the improvement on interfacial morphology and the decrease of series resistance due to better contact of the layers.

Direct synthesis of indium nanoparticles and their application to prepare CuInS2 thin films and solar cells

This paper reports a simple hot-injection method to prepare monodisperse indium nanoparticles which are applied as indium sources to prepare CuInS2 thin films and solar cells. Indium nanoparticles with particle sizes of about 10 nm or even smaller are synthesized and are influenced by the stabilizing agent, reaction temperature and solvent, which can be elucidated by a burst nucleation and growth mechanism. Moreover, the inks from the indium nanoparticles are used to prepare compact and well crystallized CuInS2 (CIS) films which are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and I–V measurement. Finally, the CIS solar cells are fabricated on the basis of the CIS films, and their efficiency is about 2.08%, which can be further improved by decreasing series resistance.

InGaN-Based Resonant-Cavity Light-Emitting Diodes with a ZrO2/SiO2 Distributed Bragg Reflector and Metal Reflector

We fabricated InGaN-based resonant-cavity light-emitting diodes (RC-LEDs) in which one of the reflectors forming the cavity was made of Ag metal and the other was a ZrO2/SiO2 dielectric distributed Bragg reflector (DBR). Ag metal was deposited onto an InGaN epitaxial layer grown on a sapphire substrate. A ZrO2/SiO2 DBR was deposited onto n-GaN after a Ag/InGaN/sapphire sample was bonded to a silicon substrate using Au bonding metal and the sapphire substrate was removed by a laser lift-off process. Multiple emission modes with a narrowed spectrum were observed with corresponding dips in the reflectance of the resonant cavity, which was examined by microreflectance measurements. The output intensity of the RC-LED was higher than that of a conventional LED and the turn-on voltage increased with a slight decrease in series resistance. The output power of the RC-LED in a 1 ×1 mm2 chip increased linearly with the injection of current up to a 500 mA.

Investigation of Al Schottky junction on n-type CdS film deposited on polymer substrate

A systematic study has been made on the behavior of Al/n-CdS thin film junction on flexible polymer substrate (polyethylene terephthalate, PET) grown using thermal evaporation method. Temperature dependence of I-V measurements for this junction has been done which closely follow the equations of Schottky barrier junction dominated by thermionic emission mechanism. Intrinsic and contact properties such as barrier height, ideality factor and series resistance have been calculated from I-V characteristics. The barrier height of Al/n-CdS junction is found to increase with increase in temperature whereas ideality factor and series resistance decrease with increase in temperature.

High efficiency polymer solar cells with vertically modulated nanoscale morphology

Nanoscale morphology has been shown to be a critical parameter governing chargetransport properties of polymer bulk heterojunction (BHJ) solar cells. Recent results onvertical phase separation have intensified the research on 3D morphology control. Inthis paper, we intend to modify the distribution of donors and acceptors in aclassical BHJ polymer solar cell by making the active layer richer in donors andacceptors near the anode and cathode respectively. Here, we chose [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) to be the acceptor material to be thermally depositedon top of [poly(3-hexylthiophene)] P3HT: the PCBM active layer to achieve a verticalcomposition gradient in the BHJ structure. Here we report on a solar cell with enhancedpower conversion efficiency of 4.5% which can be directly correlated with the decrease inseries resistance of the device.

Effect of long-term aging on series resistance and junction conductivity of high-power InGaN light-emitting diodes

The forward voltage, series resistance, and junction conductivity of commercial high-power InGaN light-emitting diodes (LEDs) were investigated as a function of aging time. A gradual decrease of series resistance with a rate of about i1%=1000 h was revealed in InGaN LEDs within rst »9,600 hours of aging under ordinary conditions (nominal forward current 350 mA, junction temperature 350 K), whereas the characteristic energy of tunnel injection exhibited a decrease with a rate of about i0.1%=1000 h. The observed aging effects were attributed to continuous post-fabrication self-annealing of the p-type cladding layer and to the variation of the localized-state density in the active layer of the LED chips.

Continuous-Wave Operation of GaN Based Multi-Quantum-Well Laser Diode at Room Temperature

Room-temperature operation of cw GaN based multi-quantum-well laser diodes (LDs) is demonstrated. The LD structure is grown on a sapphire (0001) substrate by metalorganic chemical vapour deposition. A 2.5μm × 800μm ridge waveguide structure is fabricated. The electrical and optical characteristics of the laser diode under direct current injection at room temperature are investigated. The threshold current and voltage of the LD under cw operation are 110 mA and 10.5 V, respectively. Thermal induced series resistance decrease and emission wavelength red-shift are observed as the injection current is increased. The full width at half maximum for the parallel and perpendicular far field pattern (FFP) are 12° and 32°, respectively.

Deep saturation of junction voltage at large forward current of light-emitting diodes

The dependences of series resistance, ideality factor, and junction voltage of light-emitting diodes (LEDs) on applied voltage or current were characterized accurately using alternating current (ac) behavior combined with I-V plot (acIV method). The deep saturation of junction voltage and simultaneous decrease of ideality factor of LEDs at large forward current, which imply the pinning of quasi-Fermi levels, were observed. Comparing with our recent study of the similar phenomenon of laser diodes, in which the junction voltage jumps abruptly to a saturated value at lasing threshold, the changes of junction voltage of LEDs are gradual. In addition, the decrease of series resistance with the increasing current and the negative capacitance effect of LEDs were also investigated.

Revolutional Progress of Silicon Technologies Exhibiting Very High Speed Performance Over a 50-GHz Clock Rate

Current silicon technologies are now facing very severe standstill, i.e., the operation speed is strictly limited at a clock rate of about 3.8 GHz due to the limitation of the thinning of the gate insulator film thickness because of its large amount of leakage currents through the current thermal oxide films. This typical disadvantage of current silicon technologies has been completely overcome by introducing the newly developed radical-reaction-based semiconductor manufacturing instead of the current molecule-reaction-based semiconductor manufacturing, i.e., direct nitridation films such as Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> where the gate leakage current through the insulator films has been confirmed to be decreased by a factor of at least three orders of magnitude. The speed performance of silicon large-scale integrations is enhanced to exhibit a clock rate of more than 50 GHz by introducing the balanced complementary MOS on a silicon (551) surface substrate using 3-D-structured MOS transistors, where new key technologies must be introduced, namely: 1) direct nitridation gate insulator film Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3 </sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> for 3-D MOS transistors; 2) atomic-order flat-gate insulator film/silicon interface; 3) drastically decreased series resistance of the source and drain electrodes by a factor of two orders of magnitude; and 4) introduction of the accumulation-mode MOS transistors instead of the inversion-mode MOS transistors

A Simple Model Parameter Extraction Methodology for an On-Chip Spiral Inductor

In this letter, a simple model parameter extraction methodology for an on-chip spiral inductor is proposed based on a wide-band inductor model that incorporates parallel inductance and resistance to model skin and proximity effects, and capacitance to model the decrease in series resistance above the frequency near the peak quality factor. The wide-band inductor model does not require any frequency dependent elements, and model parameters can be extracted directly from the measured data with some curve fitting. The validity of the proposed model and parameter extraction methodology are verified with various size inductors fabricated using 0.18 µm CMOS technology.

Formula omitted] noise in series resistance of LDD MOSTs

Low-doped CMOS transistors have been investigated. On the basis of the corrected optical channel length, the series resistance R s of the channel has been found from a set of MOSTs on the same chip, all having the same channel width, but differing in length. R s is about inversely proportional to the effective gate voltage V G ∗ . The 1/ƒ resistance noise of the series resistance S R s is proportional to V G ∗−3 or V G ∗−4 , depending on the implantation energy used to profile the low-doped parts of source/drain. Increasing the implantation energy from 100 to 180 keV results in a decrease in series resistance and a change in trend of its 1/ƒ noise dependence on V G ∗ . In our experiments, R s is about 15% of the total resistance and S R s 20% of the total noise power in a short-channel MOST at V G ∗ = 1 V .

The photoelectrochemical studies on CdS: Cu: Cl electrodes: Importance of photoconductivity effects

The photoelectrochemical characterisation of highly photosensitive and semi-insulating sintered pellets of CdS doped with Cu and Cl has been carried out. In the course of this work, we have observed a complete suppressin of the dark current but a pronounced photocurrent under cathodic polarisation. Both these observations indicate an unusual cathodic (i.e. forward bias) behaviour. It has been shown that due to a decrease in series resistance under illumination by an extrinsic photoconductivity effect, the “ideal” cathodic behaviour, i.e. normally found in dark for an n-CdS electrode with low resistivity, can get restored. We have also observed a red shift in the anodic photoelectrochemical spectral response of these samples. It is in agreement with our previous photoelectrochemical studies on CdS: Cu: Cl electrodes and can be explained by considering a Cu impurity excitation process. Additionally, we have observed that the background illuminations as such (employed in the “double-beam” technique of spectral response determination) do not alter the overall nature of the spectral response but result in an interesting photocurrent enhancement phenomenon. These photocurrent enhancement observations have been explained by taking into account the photoeffects at Cl-compensated Cu acceptor centers possessing a high capture cross section preferably for photoexcited holes.

Electrical and photovoltaic properties of amorphous chalcogenide thin-film p-n junctions

Amorphous chalcogenide thin-film p-n junctions have been formed between p-type As2Se3 or Ge20Se80 and n-type Ge20Bi15Se65. The rectifying behavior was observed only for the junctions which were formed by depositing the p-type films on the annealed n-type films. The forward currents in these junctions were found to be space-charge-limited, as in the previously formed p-type film/n-type bulk glass junctions. The photovoltaic properties of the thin-film p-n junctions have been improved, compared with the film/bulk glass junctions, due to the decrease in series resistance of the cells.

Studies of axon-glial cell interactions and periaxonal K + homeostasis—III. The effect of anisosmotic media and potassium on the relationship between the resistance in series with the axon membrane and glial cell volume

The effect of anisosmotic physiological solutions and [K +] 0 on the resistance in series with the axon membrane were studied in medial giant axons of the crayfish, Procambarus clarkii, to determine if changes in series resistance are correlated with changes in glial cell volume and volume regulatory responses. Series resistance was estimated from computer analysed voltage waveforms generated by constant current and space clamp techniques using piggy-back axial wire current passing and glass pipette recording electrodes. Axons subjected to anisosmotic physiological solution in the range of 23 to 175% of isosmolar solution demonstrated that the series resistance of axons changes in a manner similar to that expected for a volume change in isolated cells. In hyperosmotic solution the series resistance changes biphasically, initially decreasing followed by a recovery of the series resistance, similar to the regulatory volume increase described for glial cells in culture. The increase in series resistance following the initial decrease is inhibited by bumetanide (0.1 mM). Ouabain (1 mM), an inhibitor of the volume decreasing Na-K pump, causes the series resistance to increase significantly above that seen for the no-drug control. Bumetanide, an inhibitor of the volume increasing Na-K-Cl cotransporter, inhibits the volume regulatory response to anisosmotic media. Treating the axon with three times normal external [K +] causes the series resistance to decrease approximately 15% while five times normal [K +] leads to a 15% increase in series resistance. Both ouabain and d-tubocurare (10 −8M) prevent the three-fold [K +]-induced decrease in series resistance while carbachol (10 −8M) and bumetanide have little effect. On the other hand, ouabain enhances the five-fold [K +]-induced increase in series resistance while carbachol and bumetanide cause the five-fold [K +] response to be in a decreasing direction. d-Tubocurare has little effect on the five-fold [K +]-induced increase in series resistance. The study demonstrates that under the conditions of these experiments changes in series resistance are a reflection of changes in cell volume modulated by ouabain- and bumetanide-sensitive K + uptake mechanisms. The effects of carbachol and d-tubocurare on the series resistance suggest that their effects are modulated through their actions on the glial cell membrane potential and the electrochemical gradient for K +, which in turn controls the amount of K + that appears in the periaxonal space. A comprehensive model for K + homeostasis of the periaxonal space is presented and integrates the influences of glial transport processes and cholinergically controlled membrane potential of the glial cell at rest and during action potential generation.

Theory for voltage dependent series resistance in silicon solar cells

A distributed parameter model has been proposed for p- n junction solar cells to account for the variation of series resistance due to the forward biasing of the p- n junction under external injection condition. The theoretical expression developed using this model predicts a coupling between base and emitter via depletion layer. This coupling becomes stronger with increasing bias and is found to be responsible for the observed decrease of series resistance with rising injection level. Numerical results of our theory are found to agree well with those obtained from experiments.

Graphical method for the evaluation of series resistance in solar cells

A graphical method for the evaluation of series resistance (R s) has been proposed after solving the dark and illuminated current-voltage equations for junction solar culls. The design of an electronic circuit has been described to obtain idea) open and short circuit condition? and the measurement of R s has been reported for a few diffused junction silicon solar cells as a function of illumination level up to∼2 gun. It has been found that the series resistance decrease sharply with intensity of incident radiations up to∼1 sun and it saturates with further increase of intensity

Microwave Characterization of Varactor Diodes and the Effect of Their Dynamic Quality Factor on the Performance of Parametric Amplifier

A reflection technique has been developed for the measurement of the dynamic quality factor of varactor diodes. Several diodes with varying design parameters were fabricated at CEERI and their measured at 4-GHz. It has been observed that of the diodes improves with increasing cut-off frequency fc and decreasing series resistance Rs. These diodes were successfully used in a 4-GHz negative resistance parametric amplifier also developed at CEERI. It is shown that the maximum gain (G)max and the minimum noise figure (NF)min of the amplifier improve with increasing of the diode.

Evaluation of voltage dependent series resistance of epitaxial varactor diodes at microwave frequencies

The series resistance of a high-quality varactor diode is primarily determined by the resistance of the semiconductor material close to the junction. With increasing reverse bias, the width of the space-charge region becomes greater, and the series resistance decreases. Theoretical models of graded and step junctions have been assumed, and calculations have been made of the series resistance as a function of bias. Epitaxial silicon diodes have been measured for series resistance as a function of bias by using the transmission loss method at 6 to 12 Gc/s, with the diode mounted across a reduced-height waveguide. The variation of series resistance with bias agrees well with the theoretical calculations. By measuring of the 3-dB bandwidth of the series resonance of the diode mounted in the reduced-height waveguide, the junction capacitance and the effective series inductance of the package also can be determined. Because the width of the space-charge region must vary with applied voltage in order to obtain the varactor characteristic, the diode cannot have zero-series resistance at zero-volt bias. The minimum possible series resistance is a function of the breakdown voltage and increases with increasing breakdown voltage. Calculations of the maximum possible cutoff frequency as a function of the diode breakdown voltage are presented for both graded and step junction silicon varactors. A plot of series resistance vs. reverse bias can be used to determine the impurity concentration profile in the epitaxial film. The impurity concentration profile can also be determined by measuring the capacitance vs. reverse bias, a technique which has been in use for some time. However the former method appears to be more accurate in that it is independent of junction area.