Temperature Dependence Of Voltage Research Articles

Investigation on temperature dependence of recent high-efficiency silicon solar modules

The temperature dependence of photovoltaic modules varies with temperature and irradiance. For recent high-efficiency solar modules such as silicon heterojunction (SHJ) solar modules and tunneling oxide passivated contact (TOPCon) solar modules, it is not clear how their temperature dependence changes with temperature and irradiance. In this study, the temperature dependence of SHJ and TOPCon solar modules was studied by measuring I–V curves with the irradiance ranging from 200 to 1000 W/m2 and temperature ranging from 25 to 75 °C. The passivated emitter and rear cell (PERC) solar modules were measured as a reference. The results indicate that the temperature dependence of short-circuit current (Isc) for the three modules is almost invariable with temperature and irradiance. The temperature dependence of open-circuit voltage (Voc) and maximum power (Pm) decreasees with the increasing module temperature, and increasees with the increasing irradiance. It can be observed that the absolute magnitude of (∂Pm/∂T)/Pm for SHJ is the smallest, which is more obvious at high irradiance. An interesting finding is that the temperature dependence of fill factor (FF) for SHJ solar module increases with increasing irradiance, which is opposite to PERC and TOPCon solar modules. This phenomenon is related to the temperature dependence of series resistance. In addition, the temperature dependence is not linear at low temperature and irradiance. The obtained results in this paper can provide useful insight into predicting performance ratio of PERC, SHJ and TOPCon solar modules.

The critical role of temperature-dependent mobilities in determining the open-circuit voltage of bulk-heterojunction organic solar cells

While solution-processed bulk-heterojunction organic solar cells (OSCs) continue to attract attention as their efficiencies approach 20%, the physical origin of the non-radiative energy loss in OSCs remains under debate. Understanding the temperature dependence of open-circuit voltage (VOC) is thus important because it provides unique insights into the origin of energy loss. Herein, we simulate the VOC vs T relation of PTB7-Th:PC71BM bulk-heterojunction OSCs within the range of 160–295 K by incorporating experimentally measured temperature-dependent mobilities into the drift-diffusion model, assuming bimolecular recombination as the primary recombination mechanism. Significantly, we find that the temperature dependence of VOC can only be correctly reproduced by the model when the temperature dependence of the carrier mobilities is taken into account. The effect of the Langevin reduction coefficient on the temperature dependence of VOC is also investigated.

The interplay between anomalous metallic and superconducting states tuned by disorder in thin flakes of Kagome metal KV3Sb5

Recently, V-based Kagome metals have attracted intense attention due to the coexistence of their topological nontrivial electronic structure, charge density wave, and superconductivity. Here, we report the fabrication and physical investigations of single-crystalline thin flakes of the Kagome metal KV3Sb5. For samples with a thickness of , Berezinskii–Kosterlitz–Thouless type behavior is revealed by the temperature dependent resistance and voltage–current data, which indicates the presence of two-dimensional superconductivity. Meanwhile, a temperature-independent resistance behavior is observed in a wide field region, supplying the hallmark of the anomalous metallic (AM) state. Importantly, by comparing the interplay between the superconducting and AM states of two samples with different levels of disorder, a striking competitive evolution with the external field between these two states is uncovered.

Comparing the loss of charge carrier generation with the loss of V OC at low temperatures in organic bulk-heterojunction blends

Abstract We estimate the temperature dependence of charge carrier generation in P3HT:ICBA and PTB7:PCBM using continuous-wave photoinduced absorption. For P3HT:ICBA, the generation rate increases fivefold from 79 K to ca 250 K, above which it saturates. We compare this to the temperature dependence of open-circuit voltage (V OC) which at low temperatures shows a decrease with decreasing temperatures, in disagreement with the typically expected linear rise. This voltage loss is too large to be explained by the decrease of generation with decreasing temperature. For PTB7:PCBM the dominant species has a generation rate increasing from 90 to 150 K, after which it decreases. For PTB7:PCBM there is no decrease in V OC at low temperatures. Our findings support the lack of correlation between the decrease in V OC and a decrease in generation rate. We conclude that the loss of V OC does not originate in charge carrier dynamics in the bulk material, but is due to contact effects.

Active Area Temperature Measurement of Medium-Power LEDs by Dynamics Changes in Forward Voltage during Current Heating and Cooling

The most common non-destructive methods of measuring the temperature of the active area of light emitting diodes (LEDs) are briefly analysed and their disadvantages are pointed out. Measurements of the temperature of the active area of medium-power LEDs by the dynamics of change in the direct voltage during heating by currents of different densities and in the process of cooling in the mode of flow of small, so-called measuring current, which not cause heating of LEDs, are presented. An electrical scheme realising the used method is given. The results of measurements show that the thermal resistance of LED, determined by the results of measuring the temperature of the active area by the proposed method, is greater than the reference value. The comparison of the results of temperature measurements using traditional methods of analysing the radiation spectra of LEDs and the temperature dependence of direct voltage is carried out.

Characterisation of SiC Varistor Quench Protection Operating at 4 Kelvin for Use With Superconducting Magnets

Silicon carbide (SiC) composite high-energy varistors have been demonstrated as a viable alternative to linear resistors as energy extraction devices during an abrupt loss of superconductivity in a magnet, called a quench. These have typically been installed external to the cryostat at ambient temperatures, but for some superconducting magnets it may be beneficial to mount the varistors within the cryostat in vacuum, a gaseous environment, or submerged in liquid cryogens. Varistors are semiconductors and therefore exhibit a temperature-dependent voltage–current relationship, so characterising their behaviour at low temperatures is important to predict their energy extraction behaviour. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">In this paper we present characterisation data of SiC varistor devices from 4–300 K: voltage-current characteristics, thermal conductivity, specific heat capacity, thermal expansion, and flexural strength. These varistors are a candidate for protection at 1.9 K of the MCBY magnets, currently being built at Uppsala University for CERN.

How can we turn heat into useful energy using nanotechnology?

In 1821, the German physicist Thomas Seebeck made a groundbreaking discovery that revealed the direct conversion of heat energy into electricity. He did so by bringing two different metals together and holding one end heated and the other end cooled. This process is famously known as the Seebeck effect. William Thomson, a British physicist later known as Lord Kelvin, further developed the concept of thermoelectric circuits and introduced the idea of a temperature-dependent voltage in a circuit made of two dissimilar metals. Lord Kelvin’s contribution to the field of thermoelectricity paved the way for various applications in temperature sensors, power generators, refrigeration, and cooling systems.

Self-driven thermoelectric cooling contraption for liquid metals under the static magnetic field

The presence of large temperature gradients in liquid metals during heat transfer can also induce thermoelectric effects, which can lead to pumping or stirring of liquid metals under the action of magnetic fields. The thermoelectric effect of liquid metals has potential application background in both nuclear fusion and metal metallurgy. In this paper, an experimental study of flow driven by the Seebeck effect, in which the temperature-dependent voltage difference at an interface between dissimilar metals, in the presence of a magnetic field, can be used to create a Lorentz force. It is proposed that this method could be used for cooling electronics, fusion reactors, and solar technologies. The working fluid is eutectic gallium–indium–tin, and flow measurements are made with ultrasound. The flow velocity tends to increase and then decrease as the magnetic field increases. Two scaling relations are developed to predict the velocity, one for weak magnetic fields and one for strong magnetic fields. Those predictions are combined to estimate the maximum velocity. Temperature gradients and wall conductance ratio have a significant effect on the Seebeck effect self-driven flow. It is found that the self-driven flow velocity caused by the Seebeck effect is positively correlated with the number of channels in the multi-channel experiments. This design idea of self-generated flow and heat transfer of liquid metal in the magnetic field will provide the possibility of pumpless self-driven liquid lithium flow in nuclear fusion reactors and provide new ideas for cooling of electronic products and related energy-saving and emission reduction applications.

A 1.2-V 0.959-ppm/°C multi-section curvature-compensated bandgap voltage reference with trimming

This article introduces a high-precision and low temperature coefficient(TC) bandgap reference (BGR) with a 1.2 V output voltage after a novel digital trimming. A multi-section curvature compensation circuit alleviates the variation caused by the temperature dependence of the base emitter nonlinear voltage of bipolar transistors. The novel digital trimming technology is utilized to reduce the TC and improve the output voltage precision(VP) of the proposed the BGR. Designed and simulated in a 65 nm CMOS process with an active area of 0.037 mm2. Simulation results of the proposed the BGR demonstrates that its output voltage is 1.2 V, the best TC is 0.959 ppm/°C over a −40 °C to 125 °C temperature range and the power consumption of 138 μW under 3.3 V supply voltage at room temperature with trimming. In the supply voltage range of 1.8–3.4 V, the line regulation (LR) is 0.25%/V.

Температурная зависимость напряжения шнурования тока в мощных ВЧ и СВЧ биполярных транзисторах

The results of studies of the temperature dependence of the voltage UKL of current lacing in power RF and microwave bipolar transistors (PBT) in the temperature range from - 60 to 90 ° C on the upgraded unit UITEP-M for measuring the thermoelectric parameters of high-power transistors are presented. The principle of operation of the installation is based on measuring the amplitude of the variable component of the voltage at the emitter junction of the PBT when a constant emitter current is passed and the sum of linearly increasing and small alternating voltage is applied to the collector; current lacing in the transistor structure manifests itself in a sharp increase in the steepness of the dependence. On a sample of PBT type KT903A, it was experimentally established that with an increase in the temperature of the housing, the current lacing voltage decreases noticeably and at a certain temperature, the TCR reaches a minimum value of UKLmin, and then increases again with an increase in the temperature of the housing. It is shown that the greater the thermal resistance of the transistor junction-housing in the diode connection, the weaker the temperature dependence of the lacing voltage. The obtained results are qualitatively explained on the basis of a one-dimensional model.

Thin-film temperature sensors based on LPD-fabricated β-Ga2O3 Schottky diodes

We report the synthesis of wide-bandgap β-Ga2O3 nanocrystalline thin films via the low-cost and non-vacuum-based liquid phase deposition (LPD) method. The morphological evolution of the nanocrystalline β-Ga2O3 grains was investigated as a function of the growth temperature, processing time, and pH value of the precursor solution. We successfully calcined gallium oxide hydroxide GaO(OH) through a 3-h annealing process at 800 °C to convert it into β-Ga2O3. We fabricated horizontal-structured Ni/β-Ga2O3 Schottky diodes and investigated the electrical characteristics pertinent to sensing temperature in the range of 100−800 K. The temperature sensitivity of the Ni/β-Ga2O3 Schottky-junction temperature sensors, defined as the temperature dependence of junction voltage at a fixed bias current of 10 µA, peaked at −2.924 mV/K in the range between 300 and 500 K. At room temperature, we measured a barrier height of 0.915 eV and a Richardson constant of 43.04 ± 0.01 A/cm2 K2 from the Ni/β-Ga2O3 Schottky junctions. These results indicate that the LPD-synthesized β-Ga2O3 material and devices hold promising potential for sensing applications especially at high temperatures.

Bismuth composition, thickness, and annealing temperature dependence of the spin Seebeck voltage in Bi-YIG films prepared using sol–gel solution and spin-coating method

We investigated the Bi composition, film thickness, and annealing temperature (Ta) dependence of the magnitude of the longitudinal spin Seebeck effect (LSSE) voltage in BixY3-x Fe5O12 (0 ≤ x ≤ 1.2) (Bi-YIG) films on a Si substrate, prepared using sol–gel solution and spin-coating methods. The Bi-YIG garnet films exhibited a polycrystalline structure, and the thickness of the film formed by the agglomeration of nanoparticles was approximately 50 nm. The LSSE coefficient (S) of the Bi-YIG/Pt (5 nm) films tends to increase with increasing Bi composition (0 ≤ x ≤ 0.8), and the value of the S at x = 0.8 is 1.7 times larger than that at x = 0. When the Bi composition is 0 ≤ x ≤ 0.8, the values of the saturation magnetization and resistivity are almost constant regardless of x, and the value of the Gilbert damping constant increases with increasing x, while the values of the spin mixing conductance and maximum Kerr rotation angle are tended to increase with increasing x. This result indicates that the increasing tendency of the S occurs because of the induced of effective spin current conversion in the Pt layer thorough Bi-YIG due to the enhancement of interface effect between the Pt and Bi-YIG by Bi substitution. In addition, a large S is obtained in Bi-YIG films annealed at Ta = 973 K because the films contained few cracks and smooth surface conditions.

A Temperature-Compensated Crystal Oscillator With Piecewise Polynomial Varactor Compensation Achieving ±3.75-ppm Inaccuracy From −30°C to 90°C

This brief presents a low-complexity temperature-compensated crystal oscillator (TCXO). The frequency error compensation over temperature is realized by employing the proposed piecewise polynomial varactor (PPV). The PPV operation is determined by a temperature-dependent voltage generator. The temperature compensation is achieved without using an accurate mapping table and high-resolution data converters. In addition, an amplitude-control loop (ACL) is incorporated to maintain a stable XO operation under process, temperature, and supply voltage variations. This brief is fabricated in a 180-nm CMOS process. The frequency inaccuracy of the proposed 40-MHz TCXO is ±3.75 ppm from −30°C to 90 °C. Operating from a 1.8-V supply, the overall current consumption, including the proposed compensation and ACL, is 0.3 mA.

Understanding the coexistence of unipolar and bipolar resistive switching in NiFe2O4 resistive memory devices

In this Letter, spinel ferrite NiFe2O4 films prepared through pulsed laser deposition are used to fabricate Pt/NiFe2O4/Pt devices with the coexistence of unipolar resistive switching (URS) and bipolar resistive switching (BRS). The device demonstrated nonvolatile and stable resistive switching (RS) properties under URS and BRS modes. The current–voltage (I–V) fitting analysis and temperature dependence measurements suggested that one Pt/NiFe2O4/Pt RRAM cell follows two significantly different RS and carrier transport mechanisms under URS and BRS modes. Under URS mode, the carrier mechanism alternates between the high resistance state (HRS) with Schottky emission and low resistance state (LRS) with the Ohmic mechanism. In contrast, under BRS mode, carrier transport at HRS and LRS is dominated by space-charge-limited current and nearest-neighboring hopping, respectively. Finally, a physical model, combining oxygen ion (O2−) migration and electric field distribution simulated by COMSOL Multiphysics, is proposed to further clarify the coexistence of two distinct RS and carrier transport mechanisms in the single Pt/NiFe2O4/Pt RRAM device.

On the breakdown voltage temperature dependence of high-voltage power diodes passivated with diamond-like carbon

Diamond-Like Carbon (DLC) is well established material for the passivation of high voltage negative bevelled power diode. In our previous works, the conduction mechanism of the DLC has been carefully described through the characterization and the physical modelling of Metal-Insulator-Semiconductor (MIS) structures. In addition, the effects on the breakdown voltage and leakage current have been clarified comparing the available experiments with numerical simulations. However, the role played by the DLC on the breakdown voltage temperature dependence is still lacking. In this work, we addressed the latter issue and found out an anomalous reduction of the temperature dependence which is clearly ascribed to the DLC behaviour. The temperature dependencies of carrier transport in the DLC have been further investigated in order to explain the experimental results. The observed effect might be related to the release of the trapped charges with increasing temperatures or to a different temperature dependence of the DLC mobility which is function of the distance from the Si/DLC interface. TCAD simulations are used to corroborate such assumptions.

Ensemble GaAsSb/GaAs axial configured nanowire-based separate absorption, charge, and multiplication avalanche near-infrared photodetectors.

In this study, molecular beam epitaxially grown axially configured ensemble GaAsSb/GaAs separate absorption, charge, and multiplication (SACM) region-based nanowire avalanche photodetector device on non-patterned Si substrate is presented. Our device exhibits a low breakdown voltage (VBR) of ∼ −10 ± 2.5 V under dark, photocurrent gain (M) varying from 20 in linear mode to avalanche gain of 700 at VBR at a 1.064 μm wavelength. Positive temperature dependence of breakdown voltage ∼ 12.6 mV K−1 further affirms avalanche breakdown as the gain mechanism in our SACM NW APDs. Capacitance–voltage (C–V) and temperature-dependent noise characteristics also validated punch-through voltage ascertained from I–V measurements, and avalanche being the dominant gain mechanism in the APDs. The ensemble SACM NW APD device demonstrated a broad spectral room temperature response with a cut-off wavelength of ∼1.2 μm with a responsivity of ∼0.17–0.38 A W−1 at −3 V. This work offers a potential pathway toward realizing tunable nanowire-based avalanche photodetectors compatible with traditional Si technology.

Copper iodide nanoparticles as a hole transport layer to CdTe photovoltaics: 5.5 % efficient back-illuminated bifacial CdTe solar cells

We report the role of copper iodide (CuI) nanoparticles (NPs) as a hole transport layer (HTL) in cadmium sulfide/cadmium telluride (CdS/CdTe) photovoltaics. These CuI NPs were prepared using solution processing at room temperature and used to fabricate monofacial and bifacial CdTe solar cells with different back contacts. Using CuI/Au as the back contact, the device efficiency reached to 14.8% with outstanding fill factor (FF) of 79.2%. Replacing the gold (Au) electrode with sputtered transparent indium tin oxide (ITO), a CuI/ITO back contact yielded photoconversion efficiencies (PCEs) of 11.6% and 5.5% under front and back illumination respectively. Bifacial devices (CdTe/ITO) without the CuI NP HTL have an efficiency of 7.0% and 1.0% for front and back illumination, respectively. For CuI/ITO, a current collection of 12.0 mAcm−2 was observed upon back illumination which significantly improved over an ITO-only back contact (5.0 mAcm−2). The PCE obtained from back illumination was enhanced when using CuI NPs as the HTL due to the reduced back barrier height, and improved back interface as determined by temperature dependent current vs. voltage characteristics and impedance spectroscopy analysis. The improvement in device performance of the bifacial configuration is a significant step forward toward realizing thin film photovoltaic modules which harvest energy incident on the rear of the module.

Defect governed zinc-rich columnar AZO thin film and contact interface for enhanced performance of thermocouples.

The research on the stable thermoelectric properties and contact interface of high-precision thin-film thermocouples lags far behind the demand. In this study, a zinc-rich Al-doped ZnO (AZO) thin film was fabricated, in which the carriers were mainly donated by the Al dopant, and the oxygen defects migrated together, forming cage defects. Then, an indium tin oxide (ITO)/AZO thin-film thermocouple was prepared. It had a special temperature-dependent voltage curve due to the effects of cage defects on the thermoelectric properties of the AZO thin film and interfacial electron diffusion. When the zinc atoms in the cage defects were excited after annealing, a linear relationship between the temperature and voltage was obtained. The Seebeck coefficient of the thermocouple was constant at 168 μV K-1 over the entire measured temperature range. In addition, the calculated error of the thermocouple was lower than 1% from 50 °C to 500 °C, showing good repeatability. These results showed that defect engineering could effectively be used to improve the temperature range stability of thermoelectric materials and optimize the precision of thin-film thermocouples.

Sensorless Cell Temperature Estimation over the Lifetime of Lithium-Ion Batteries

The temperature distribution within a battery pack has a major impact on capacity loss, power degradation and safety issues. Therefore, monitoring the temperature of the cells in the battery pack is an essential task of a battery management system. Temperature is usually measured with external temperature sensors attached to a few crucial cells throughout the battery pack, leaving the majority of cells in larger battery packs unattended. In our recent work, we developed a method to determine cell temperatures using the temperature dependent voltage response to a current change in the load of the battery [1]. Thereby the temperature of each cell in a battery can be monitored without the need for additional temperature sensors as long as current and voltage values of the cell are available. The method relies on a DC resistance (RDC) reference to relate the voltage response to a temperature value. Since the resistance of a cell changes with the aging of the cell, the reference, and ultimately the temperature estimation method, loses its applicability with proceeding cell degradation. For this reason, we investigated the estimation method’s behavior during aging and possible ways to adjust the RDC reference. For the aging experiment, we used the same setting as in our initial work. A 6s1p module was cycled for 200 cycles, with every 5th discharge cycle being a randomized current profile, which is used for the evaluation of the temperature estimation method. The state of health (SOH) and a RDC offset are used to scale and shift the RDC reference. SOH and RDC offset were gained from checkup cycles, which were performed every 20th cycle. To maintain the online applicability of the method, only this values (SOH and RDC offset), which can be monitored by a battery management system (BMS), are considered for the adjustment of the RDC reference. We assume the SOH is a given value from the BMS and the RDC offset can be calculated from a defined or randomized pulse. The RDC offset can be used for the adjustment under the following two terms: (1) The system is in a thermal equilibrium, e.g. an electric vehicle that is parked for several hours. (2) There is at least one temperature sensor in the system. This sensor is needed to relate the RDC offset to a certain temperature. This simple adjustment strategy increased the estimation accuracy and allows the method from [1] to be used for the entire lifetime of the battery module with an average temperature estimation error of 2 K. To our knowledge, this is the first approach for resistance/impedance based temperature estimation of lithium-ion cells considering aging.[1] S. Ludwig, I. Zilberman, M.F. Horsche, T. Wohlers, A. Jossen - Pulse resistance based online temperature estimation for lithium-ion cells; Journal of Power Sources; 2021; DOI: https://doi.org/10.1016/j.jpowsour.2021.229523. Figure 1

Enhanced Dielectric Relaxation in Self-Organized Layers of Polypeptides Coupled to Platinum Nanoparticles: Temperature Dependence and Effect of Bias Voltage

Using alternative current impedance spectroscopy, we investigate the dynamical conductivity of hybrid nanomaterials composed of helical polypeptide layers containing platinum nanoparticles (PtNP). The electrical characteristics of the self-organized poly(γ-benzyl-l-glutamate) (PBGL) in bidimensional lamellar assembly in the presence of Pt nanoparticles are well modeled and described by a single equivalent circuit of parallel resistance and capacitance. The latter are determined using a comparison between the measured and calculated Nyquist plots, which allows extracting the characteristic relaxation time and frequency of the dipolar relaxation process. We found that the relaxation frequency in the PBLG–PtNP hybrid materials is enhanced by 4 orders of magnitudes compared to pure PBLG, which indicates a much faster dielectric relaxation in PBLG–PtNP due to dipole orientation and dipole–dipole interactions. The temperature dependence of the relaxation time is analyzed using Arrhenius plots, from which the activation energy of the relaxation process is found to be around 0.1 eV. Such a value close to the peptide vibration energy of the PBLG indicates a vibration-assisted relaxation process and a polaronic charge transport mechanism. An advantage of the PBLG–PtNP nanocomposite material is that the activation energy can be finely tuned by the PBLG degree of polymerization. Finally, an important outcome of this work is the investigation of the dielectric relaxation process in PBLG–PtNP under applied DC bias. We found that the activation energy decreases with increasing bias voltage for all degrees of polymerization of the PBLG molecule. This effect is interpreted in terms of electric field-induced alignment of the dipoles and of increased mobility of the polaronic charge carriers. The presence of piezoelectricity in the hybrid material gives the possibility to use the DC bias as a simple mean of monitoring the dynamical conductivity involving polaronic states.