Cell Open Circuit Voltage Research Articles

Dynamics of direct hydrocarbon PEM fuel cells

Hydrocarbon fuels contain approximately 50 times more energy per unit mass than commercial batteries, thus converting even 10% of the energy contained in hydrocarbon fuels to electrical energy could present a more mass-efficient electrical energy source than batteries. Considering the storability of hydrocarbon fuels compared to hydrogen, the viability of direct hydrocarbon polymer electrolyte membrane fuel cells was examined. With extremely pure (> 99.99%) propane, the cell Open-Circuit Voltage (OCV) was only 0.05 V and produced negligible power. However, with addition of trace quantities of unsaturated hydrocarbons, the cell had an OCV of 0.85 V and produced power, even after the unsaturated hydrocarbon addition was discontinued. At sufficiently high current densities, power output gradually decreased then the cell rapidly “extinguished” but by periodically shutting off the current for short time intervals the average power density could be increased significantly. Chemical analysis revealed that no significant amounts of hydrocarbon intermediates or CO were present in the effluent and that conversion of the hydrocarbon fuel to CO2 and H2O was nearly complete. An analytical model incorporating the relative rates of conversion of active anode catalyst sites to inactive sites and vice versa was developed to interpret this behavior. The model predictions were consistent with the experimental observations; possible physical mechanisms are discussed.

A high effciency (11.06 %) CZTSSe solar cell achieved by combining Ag doping in absorber and BxCd1-xs/caztsse heterojunction annealing

Many literatures have demonstrated that a smaller amount of Ag doping in Cu2ZnSn(S, Se)4 (CZTSSe) can elevate the open-circuit voltage (Voc) and fill factor (FF) of CZTSSe solar cells, but decrease short-circuit current density (Jsc) due to the increase in bandgap (Eg) of the CAZTSSe by Ag doping. The decreased Jsc limits the enhancement in PCE through Ag doping. In this paper, to compensate for the deficit in Jsc and further increase Voc and FF, a strategy is proposed to substitute CdS/CAZTSSe in CAZTSSe solar cells with annealed B-doped CdS/CAZTSSe. It is found that B doping can increase the electron density of CdS (ne) and decrease the lattice mismatch between CdS and CAZTSSe. Annealing can decrease the hole density of CAZTSSe (np) and passivate the surface of CAZTSSe by diffusing B towards the surface of CAZTSSe. The increased ne and reduced np widen the depletion region, leading to an increase in photogenerated carrier density (JL), resulting in an increase in Jsc. The surface passivation and decreased lattice mismatch can reduce interfacial recombination, resulting in decrease in the reverse saturation current density (J0), so further increases in Voc and FF. By optimizing the Ag doping content, B doping content, as well as the annealing temperature and time of the BxCd1-xS/CAZTSSe, the power conversion efficiency (PCE) increases from 8.96 % to 11.06 %. This study not only advances a deeper understanding of the mechanisms behind various parameters in CZTSSe solar cells but also proposes a method to boost the PCE of CZTSSe solar cells.

Breakthrough in atmospheric plasma spraying of high-density composite electrolytes: Deposition behavior and performance of plasma-sprayed GDC-LSGM on porous metal-supported solid oxide fuel cells

The potential application of plasma spraying in the preparation of ceramic electrolyte for porous metal-supported solid oxide fuel cells (SOFCs) is highlighted by its ability to eliminate the need for a high-temperature sintering process. However, the challenge of achieving highly dense electrolytes through plasma spraying remains to be addressed. In this study, a novel electrolyte for porous metal-supported SOFCs (PMS-SOFCs) is developed. This involved the preparation of a highly dense structure of gadolinium-doped ceria (GDC)-lanthanum strontium gallium magnesium oxide (LSGM) composite coating using plasma spraying under atmospheric conditions. The composite electrolyte is prepared using atmospheric plasma spraying (APS). The addition of the low-melting-point LSGM phase enhanced the microstructural densification of the GDC-based composite coating and diminished electron loss in a reducing atmosphere, thereby improving the cell's open-circuit voltage. At 36 kW plasma arc power, the single cell with composite electrolyte exhibited a maximum power density of 371 mw/cm2 at 750 °C and achieved the highest open-circuit voltage (1.03 V) at 600 °C. Moreover, the open-circuit voltage remained stable over a 100-h test. These findings suggest that using APS to deposit a composite electrolyte with added low-melting-point secondary phases presents a promising approach for achieving relatively high OCV in PMS-SOFCs based on cerium oxide electrolytes.

Preparation of CuSe nanoparticles by antisolvent process for doping and passivation of absorber layer in CdTe solar cells

The p-type doping and passivation of the back surface of the CdTe absorber layer are two key steps to enhance the performance of CdTe thin film solar cells. In recent years, different Cu-doped precursors (Cu (I) and Cu (II) materials) and passivation materials (elements such as Se, Cl, Al, etc.) have been investigated. However, few researchers have proposed in new materials on both doping and passivation functions for backside applications. Here, CuSe, which combines the potential of p-type doping and Se passivation functions, is proposed for the first time as a doping precursor for the CdTe absorber layer. A certain amount of CuSe nanoparticles was deposited on the back surface of the CdTe absorber layer based on an antisolvent deposition process. The results show that the optimal device open-circuit voltage of the CuSe-treated CdTe solar cell reaches 842.5 mV, which is ∼ 6.5 % higher than that of the CuCl2-treated CdTe device (791.4 mV). The results of current-voltage and Mott-Schottky, impedance spectrum show that the CuSe-treated CdTe device not only achieves the purpose of p-type doping, but also introduces the passivation function of Se.

Interfacial energy-band engineering for high open-circuit voltage of rear emitter p-type crystalline silicon solar cells

Rear emitter p-type crystalline silicon (c-Si) tunnel oxide passivating contact (P-TOPCon) devices with low-resistivity (≤1 Ω.cm) c-Si wafer and high-conductivity phosphorus doped (n-type) polysilicon passivating contact (n-poly-Si PC) are expected to achieve high built-in potential (Vbi) and thus open-circuit voltage (Voc). However, the results indicate that the high conductivity of n-poly-Si PC considerably deteriorates the interface passivation quality and lowers the device's Voc. A crucial factor to consider is that the hole and electron can tunnel and recombine together at the c-Si/n-poly-Si PC contact, resulting in a decrease in the quality of interfacial passivation. To inhibit carrier tunnel diffusion and enable energy band engineering at the interface for achieving high Voc, a thin intrinsic poly-Si buffer layer (10 nm) is inserted between SiO2 and n-poly-Si PC. When compared to a device without a buffer, a device with the buffer exhibits a significant improvement in passivation quality and hence Voc. The device with buffer has a Voc of 705 mV and an efficiency of 23.5 %, while that without buffer is 681 mV and 22.6 %, respectively. The introduced buffer has little effect on the industrial manufacturing process, but it does significantly enhance Voc. It has the potential to improve the efficiency of the P-TOPCon devices.

Active cooling of a photovoltaic module in hot-ambient temperatures: theory versus experiment

Abstract The performance improvement of a PV-module is investigated theoretically and experimentally in a long-term research-plan via module cooling by different approaches including passive, active, and evaporative cooling as well as water cooling for the same module. In the present paper, the investigation is conducted to decide on the suitability of active-cooling of the module in hot-ambient temperatures. A module without cooling is used as a base case for comparison against cooled modules with and without fins attached to the module’s rear-surface and extended down in an air-cooling duct underneath the module. At first, a theoretical study of heat transfer through the module is conducted to investigate how the calculated cell temperature and module output power are influenced by the air velocity from a blower, ambient temperature and solar irradiation. The results showed a decrease of cell temperature by about 7–10 °C with a subsequent increase of electrical efficiency. The cell temperature decreases significantly with the increase of duct height and with the increase of the number and length of fins, the same as in passive cooling. The cell temperature decreases by more than 3 °C at duct height of 0.2 m. The calculated values of cell temperature, open-circuit voltage and short-circuit current of the module with and without active cooling agreed reasonably with the present measured values over the day hours of two successive days in summer season. At air velocity of 1.5 m/s, the increase of electrical efficiency by active cooling was found 0.67–0.80 %. Further increase of air-flow velocity or duct-height in active cooling seeking higher efficiency is not recommended due to increase of consumed electric power by air-blower and limited decrease of cell temperature. This concludes that air cooling is not effective in regions of hot ambient temperatures. For a non-cooled module, the cell temperature is related to the ambient temperature in terms of the solar radiation and NOCT, the datasheet value of normal-operating-cell-temperature. The relationship is modified in the present paper to account for air-flow through the duct seeking its extension for application to air-cooled modules.

Efficiency and stability enhancement in FA-based perovskite solar cells using controlled reduction of graphene oxide interlayer – An experimental investigation

Reduced graphene oxide (rGO) as an interlayer and interface engineer, due to its conductivity and hydrophobicity, can be coated on top of perovskite layers to increase the photovoltaic performance and stability of perovskite solar cells. Herein, we employed reduced graphene oxide as an interlayer. By controlling the reduction level of rGO, its potential for boosting perovskite solar cells' efficiency was further increased. Results showed that increasing the reduction degree of rGO to an optimal level increased its conductivity and hole mobility, which induced charge transfer at perovskite/hole transport layer and increased the open-circuit voltage of solar cells. Our rGO reduction controlling strategy enables FAPbI3-based solar cells to record a PCE of 22.29%. In addition, increasing reduction degree increased hydrophobicity behavior of rGO. It increased perovskite solar cell resistance against humidity and heating degradation. The developed method in current study can push up perovskite solar cells to industrialization.

Achieving high open-circuit voltage in efficient kesterite solar cells via lanthanide europium ion induced carrier lifetime enhancement

Short carrier lifetimes is a key challenge limiting the open-circuit voltage (VOC) and power conversion efficiency (PCE) of kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. In this work, for the first time, lanthanide europium (Eu) ions have been introduced into Ag-incorporated CZTSSe absorber layer, which can modify the selenization reaction pathway during the initial selenization process, leading to high-quality (Ag, Eu)-CZTSSe absorber with large compact crystal grains and benign surface potential fluctuations. This innovative absorber engineering can also optimize defects dynamics with less detrimental defects and defects-assisted non-radiative recombination. Thus, significantly enhanced minority carrier lifetimes from 0.97 to 3.15 ns can be achieved, representing one of the top values among various bulk and/or interface engineering treated CZTSSe. The champion CZTSSe thin-film solar cell exhibits an impressive VOC of 545.6 mV, accompanied with a stimulating increase in PCE from 10.68% to 13.30%. These findings underscore the potential of lanthanide cation doping to drive significant advancements in CZTSSe photovoltaic technology, and therefore promoting its further development and future applications.

Development software program for finding photovoltaic cell open-circuit voltage and fill factor based on the photovoltaic cell one-diode equivalent circuit model

Development software program for finding photovoltaic cell open-circuit voltage and fill factor based on the photovoltaic cell one-diode equivalent circuit model

A multisource energy harvesting circuit for vibration and light energy with MPPT

SummaryThe article presents a multisource energy harvesting circuit (MEHC) for vibration and light energy with maximum power point tracking (MPPT). The MEHC has a cold start capability and extracts energy from piezoelectric transducers (PZTs) and photovoltaic cells (PVs) simultaneously when the multi PZTs reach their peak open‐circuit (OC) voltage, detected by the peak voltage detector and the PV1 cell voltage exceeds the MPP voltage (MPP voltage is approximately 0.7 times the PV cell's OC voltage) during the off‐peak time of the PZTs. The experimental results indicate that the output power of the MEHC is 2.8 mW under certain conditions, and the maximum energy extraction efficiency of the PVs is about 75%. The output power of the MEHC is 4.59 times of that without PVs.

An A′–A–DA′D–A–A′-type acceptor enables organic solar cells with high VOC and low nonradiative voltage loss

A novel A′–A–DA′D–A–A′ typed acceptor was developed, where the benzotriazole unit was used as the A′ unit both on the central core and terminal groups, to reduce the voltage loss and to increase the open-circuit voltage in efficient organic solar cells.

Methanol as an anti-solvent to improve the low open-circuit voltage of CsPbBr3 perovskite solar cells prepared with water.

CsPbBr3 has received more and more attention in the field of optoelectronic devices due to its excellent stability. To address the cost and environmental concerns associated with the use of toxic methanol, water has been explored as a substitute solvent for CsBr in the preparation of CsPbBr3 perovskite solar cells (PSCs). In this study, we utilized methanol as an anti-solvent of the CsBr/H2O solution to regulate the detrimental effects of water on the CsPbBr3 film and control the crystallization process. From results of the experiment, it was found that methanol anti-solvent treatment greatly improved the crystallization of the CsPbBr3 film, increased the grain size, and reduced the defect density. After the introduction of methanol anti-solvent treatment, the power conversion efficiency (PCE) increased from 6.09% to 7.91%, while the open-circuit voltage (Voc) increased from 1.18 V to 1.39 V. Furthermore, we incorporated 2-hydroxyethylurea into the CsPbBr3 PSCs to improve the wettability of PbBr2 towards the CsBr/H2O solution and ensure the formation of pure-phase CsPbBr3 films. The introduction of 2-hydroxyethylurea resulted in an additional increase in Voc from 1.19 V to 1.42 V. The PCE further improved from 6.56% to 8.62% after methanol anti-solvent treatment. These results demonstrate that methanol treatment effectively addresses the low Voc issue observed in CsPbBr3 PSCs prepared with water as a solvent. Importantly, this approach significantly reduces the reliance on methanol compared to conventional fabrication methods for CsPbBr3 PSCs. Overall, this work presents a promising pathway for achieving high Voc and efficiency in CsPbBr3 PSCs by utilizing water as a solvent.

Top cell design and optimization of all-chalcopyrite CuGaSe<sub>2</sub>/CuInSe<sub>2</sub> two-terminal tandem solar cells

Solar cells have attracted much attention, for they can convert solar energy directly into electric energy, and have been widely utilized in manufacturing industry and people’s daily life. Although the power conversion efficiency (PCE) of single-junction solar cells has gradually improved in recent years, its maximum efficiency is still limited by the Shockley-Queisser (SQ) limit of single-junction solar cells. To exceed the SQ limit and further obtain high-efficiency solar cells, the concept of tandem solar cells has been proposed. In this work, the chalcopyrite CuGaSe<sub>2</sub>/CuInSe<sub>2</sub> tandem solar cells are studied systematically in theory by combining first-principle calculations and SCAPS-1D device simulations. Firstly, the electronic structure, defect properties and corresponding macroscopic performance parameters of CuGaSe<sub>2</sub> (CGS) are obtained by first-principles calculations, and are used as input parameters for subsequent device simulations of CGS solar cells. Then, the single-junction CGS and CuInSe<sub>2</sub> (CIS) solar cells are simulated by using SCAPS-1D software, respectively. The simulation results for the single junction CIS solar cells are in good agreement with the experimental values. For single-junction CGS cells, the device simulations reveal that the CGS single-junction solar cells have the highest short-circuit current (<i>J</i><sub>sc</sub>) and PCE under the Cu-rich, Ga-rich and Se-poor chemical growth condition. Further optimization in the growth environment with the highest short circuit current (<i>J</i><sub>sc</sub>) shows that the open-circuit voltage (<i>V</i><sub>oc</sub>) and PCE of CGS solar cells can be improved by replacing the electron transport layer (ETL) with ZnSe. Finally, after the optimized CGS and CIS solar cells are connected in series with two-terminal (2T) monolithic tandem solar cell, the device simulation results show that under the growth temperature of 700 K and the growth environment of Cu-rich, Ga-rich, and Se-poor, with ZnSe serving as the ETL, the CGS thickness of 2000 nm and the CIS thickness of 1336 nm, the PCE of 2T monolithic CGS/CIS tandem solar cell can reach 28.91%, which is higher than the ever-recorded efficiency of the current single-junction solar cells, and shows that this solar cell has a good application prospect.

Boosting the fill factor and open-circuit voltage of carbon-based perovskite solar cells with a graphene co-doped P3HT/NiOx hole-transporting bilayer

A low-temperature and solution-processed graphene co-doped G-P3HT/G-NiOx hole-transporting bilayer with enhanced conductivity and matched cascade band alignment is designed for high-performance carbon electrode perovskite solar cells.

Capacitor-Based Active Cell Balancing for Electric Vehicle Battery Systems: Insights from Simulations

Abstract Cell balancing, a critical aspect of battery management in electric vehicles (EVs) and other applications, ensures a uniform state of charge (SOC) distribution among individual cells within a battery pack, enhancing performance and longevity while mitigating safety risks. This paper examines the effectiveness of capacitor-based active cell-balancing techniques using simulations under dynamic loading conditions. Utilising MATLAB and Simulink, various circuit topologies are evaluated, considering real-world cell parameters and open-circuit voltage (OCV) curve modelling. Results indicate that advanced configurations, such as double-tiered switched-capacitor balancing, offer improved balancing speed and efficiency compared to conventional methods. However, challenges such as transient events during charging and discharging phases underscore the need for further research. By leveraging simulations and experimental data, researchers can refine cell-balancing strategies, contributing to the development of safer, more efficient battery systems for EVs and beyond. This study underscores the importance of systematic analysis and optimisation in advancing cell-balancing technology for future energy-storage applications.

Evaluation of Open Circuit Voltages (OCV) of Microbial Fuel Cells from Cow and Pig Dungs

A microbial fuel cell (MFC) has many potential applications, including wastewater treatment, environmental monitoring and bioenergy production. The comparison of the open circuit voltages OCV values for three MFC set-ups using cow dung, pig dung and the combination of cow and pig dungs was carried out in this study. The MFC fabricated locally consist of two chambers – the anode, which is an anaerobic digestion of organic waste with an electrode on top of the digester lid while potassium permanganate was mixed with water in a chamber to form the cathode with an electrode on top of the lid. The two chambers were linked with a proton exchange membrane (PEM) made with agarose agar using PVC pipe. For 30 days, the OCV of the MFC set-ups were recorded. The OCV values for the three set-ups were compared. According to the results, the average OCV values for cow dung, pig dung, and a mixture of both are 1.014 V, 0.610 V and 0.430 V, respectively. This shows that cow dung produced the highest OCV values, followed by pig dung. The OCV values from the mixture of both had the lowest results.

Structure-Property Relationships for the Electronic Applications of Bis-Adduct Isomers of Phenyl-C61 Butyric Acid Methyl Ester.

Higher adducts of a fullerene, such as the bis-adduct of PCBM (bis-PCBM), can be used to achieve shallower molecular orbital energy levels than, for example, PCBM or C60. Substituting the bis-adduct for the parent fullerene is useful to increase the open-circuit voltage of organic solar cells or achieve better energy alignment as electron transport layers in, for example, perovskite solar cells. However, bis-PCBM is usually synthesized as a mixture of structural isomers, which can lead to both energetic and morphological disorder, negatively affecting device performance. Here, we present a comprehensive study on the molecular properties of 19 pure bis-isomers of PCBM using a variety of characterization methods, including ultraviolet photoelectron spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, single crystal structure, and (time-dependent) density functional theory calculation. We find that the lowest unoccupied molecular orbital of such bis-isomers can be tuned to be up to 170 meV shallower than PCBM and up to 100 meV shallower than the mixture of unseparated isomers. The isolated bis-isomers also show an electron mobility in organic field-effect transistors of up to 4.5 × 10-2 cm2/(V s), which is an order of magnitude higher than that of the mixture of bis-isomers. These properties enable the fabrication of the highest performing bis-PCBM organic solar cell to date, with the best device showing a power conversion efficiency of 7.2%. Interestingly, we find that the crystallinity of bis-isomers correlates negatively with electron mobility and organic solar cell device performance, which we relate to their molecular symmetry, with a lower symmetry leading to more amorphous bis-isomers, less energetic disorder, and higher dimensional electron transport. This work demonstrates the potential of side chain engineering for optimizing the performance of fullerene-based organic electronic devices.

Investigation of the open-circuit voltage of non-fullerene acceptors-based ternary organic solar cells based on interpretable machine-learning approach and chemically inspired descriptors

Ternary strategy to enhance the photovoltaic performances (e.g., open-circuit voltage (Voc), current density (Jsc), fill factor (FF), and power conversion efficiency (η)) of non-fullerene acceptors (NFAs)-based organic solar cells (OSCs) has exhibited alluring potential for next generation photovoltaic technology. However, the prediction and optimization of Voc in NFA-based ternary OSCs through expensive and time-consuming experiments or a theoretical perspective (e.g., an empirical rule for Voc prediction of the donor–acceptor binary system) is still an open challenge, mainly because of the complicated ternary photoactive layers. In this study, the prominent predictive performance (R2 > 0.7) of Voc is obtained by utilizing the technique of machine-learning combined with specific descriptors (e.g., frontier molecular orbital theory or electrophilicity index (ɷ)), for the first time forNFA-based ternary OSCs. Furthermore, the Shapley additive explanation (SHAP) model is employed to provide both global and local interpretable explanations for exploring the interpretability of the (eXtreme Gradient Boosting (XGBoost) model prediction and extracting the complex correlation between the specific descriptors and the Voc of NFA-based ternary OSCs. The proposed interpretable machine-learning strategy can contribute to the predictive modeling of highly efficient ternary OSCs based on multicomponent photoactive layers.

Battery Emulator for Coupled Electro-Thermo Powertrain Testing

Approved, DCN# 543-443-23Battery emulation systems are useful for testing and evaluating powertrain systems; but typically,only consider the electrical characteristics of a battery. Powertrains with shared cooling components/systems between batteries and power electronics would benefit from hardware-in-the-loop testing facilities that consider both the electrical and thermal aspects of energy storage. In this work a battery emulator that physically emulates both the electrical and thermal characteristics with a coupled electro-thermal powertrain testbed is demonstrated. The coupled electro-thermo model links the electrical and thermal outputs together and calculates them in real-time. The electrical model is an equivalent circuit representation of a battery making use of experimental data from tested cells. The electrical model is coupled to the thermal model through temperature-dependent parameters of the cell resistance and open circuit voltages. The thermal model is a lumped isothermal reduced order heat generation model. This model will calculate the net heat generated from the ohmic losses, entropic losses, and losses to cooling (liquid and ambient). The thermal model is coupled to the electrical model by being dependent on the cell’s state of charge and using the cell’s current and voltage outputs for its governing equations. Models are parameterized on experimental data acquired through pulsed hybrid testing. In this work, a 3.5 kWh battery pack with a discharge of 40 amps at 48 volts generating 38.4 Watts of heat is emulated in an electro-thermo powertrain testbed configured to represent an electric naval platform such as a small autonomous boat subjected to both baseline and pulsed loading. The electrical emulation is performed through a bidirectional power supply and thermal emulation through a resistive heater. The electro-thermo powertrain testbed then dissipates the emulated electrical energy through power convertors and electronic loads while the thermal energy is dissipated through a heat exchanger that also cools the power convertors. Numerical and experimental validation demonstrate that the coupled electro-thermo battery emulator is capable of accurately representing the electrical and thermal aspects of a 3.5 kWh battery. Limitations in terms ofemulating batteries at higher temperatures and current draws are discussed. Effects of scaling the coupled electro-thermo battery emulator are also presented.Acknowledgment: This work was supported in part by the Office of Naval Research under contract NO.N00014-22-C-1003DISTRIBUTION STATEMENT A. Approved for public release: distribution unlimited

Surface Photovoltage Method for Photovoltaic Quality Control of GaAs-Based Solar Cells

In this paper, we demonstrate the potential of the contactless surface photovoltage (SPV) method for fast and reliable control of GaAs-based solar cells directly on epitaxial heterostructures before metallization and photolithography processes. The magnitude of the SPV corresponds to the generated photovoltage in the photoactive region, which is related to the open circuit voltage of the cell. The focus of this investigation is the potential of dilute nitride compounds grown by low-temperature liquid-phase epitaxy (LPE) for application as intermediate cells in multijunction solar cells. First, SPV spectroscopy is used to determine the photosensitivity spectral range and bandgap of the grown dilute nitride compound layers. Further, the photovoltaic quality of the grown solar cell heterostructures is evaluated by comparing the magnitude of their SPV signals with that of a reference GaAs solar cell. A drastic reduction in the measured SPV is observed for nitrogen-containing solar cell structures, which correlates with the lowering of solar cell open-circuit voltage values measured under standard test conditions. Finally, solar cell structures based on nitrogen-free GaAsSb compounds with the same long-wavelength photosensitivity limit as GaAsSbN are grown by LPE. They show one order of magnitude higher SPV signal and, therefore, have a great potential for solar cell application.