Decrease In Cell Efficiency Research Articles

Studying effect of temperature on the efficiency of solar cells through the interpolation method

The objective of this paper is to present a comparative study between the traditional least squares method 'LSM' and the new method of "Polynomial Interpolation at Different Orders" for extracting the electrical parameters of a silicon solar cell. The focus is on the advantages and disadvantages of each approach. The results indicate that fourth-order interpolation yields the best results, but it is challenging to implement because the J-V function is neither linear nor transcendental. Therefore, we opted for the first-order Piecewise Linear Interpolation 'PLI' in the range where the J-V characteristic is nearly flat, i.e., the interval where the voltage varies from 0 to Vmax. By utilizing the first-order derivative of the function f(J, V) with two variables and MATLAB fzero function, we were able to determine the five critical parameters for our solar cell: the series resistance RS, the shunt resistance RSh, the light-generated current density Jph, the reverse saturation current density J0, and the ideality factor n. We used the Bland-Altman technique to evaluate the comparability between the two methods. The results obtained using this technique show that all the data points lie within the confidence interval. This indicates that the piecewise interpolation method provides J-V characteristic values very similar to those found by the LSM method. The strength of the new method lies in its speed, practicality, and the fact that it does not require initial values for the solar cell parameters. Additionally, it avoids the need to determine the variation intervals for each parameter and the use of complex functions such as the Lambert W function, which is necessary in the LSM method. By applying this method, we examined how the electrical parameters behave when the temperature varies from a cold region (0 °C) to a hot region (50 °C). The analysis of the results obtained by both scientific methods, namely the LSM method and polynomial interpolation, reveals a decrease in cell efficiency from 19.63 to 13.73 %. Similarly, the open-circuit voltage decreases from 0.62 to 0.524 V, and the ideality factor also decreases from 2.2 to 1.54. The current decreases from 39.50 to 34.30 mA/cm2 as the temperature increases from 0 °C to 30 °C, then stabilizes at 34.30 mA/cm2 for temperatures ranging from 30 °C to 50 °C.

Impact of string connection and contact defects on electrical current distribution in solar cells and modules: A model validated by magnetic field imaging

AbstractModeling of solar modules and their components is essential to quantify geometrical, optical, and electrical losses and to improve the designs and technologies in terms of performance. In most loss analysis models, the current share among the busbars of the solar cell is assumed to be equal since a symmetrical distribution of the metallization is given. The impact of string terminal connection on the current distribution among the ribbons and the resulting changes in ohmic losses has not been studied yet. In this study, a MATLAB model is developed to consider the impact of the string connector terminal position on the current distribution and the ohmic losses in the ribbons and in string connector. The model allows for the analysis of the impact of contact defects scenarios in ribbons and string connectors on the current distribution. Results show that the highest current flows at the closest busbar to the string connector terminal while the current decreases at the busbars farther away from the terminal due to higher ohmic resistance of the current path. The higher the ohmic resistance of the string connector, the more inhomogeneous the current share at busbars. Simulating a 9 busbar M6 half‐cell with 1 × 0.08 mm2 string connector, positioning the string connector terminal at the leftmost or rightmost ribbon results in 0.4 W less power compared to center connection configuration, where the string connector terminal is positioned at the center ribbon. Furthermore, simulation results show that inhomogeneity of current causes about 2.1% reduction in module power compared to the case of evenly distributed cell current, considering a 120‐haf‐cell module with the same string connector. Regarding contact defect analysis, exemplary simulations show the impact of the position of detached ribbons on the power or efficiency loss. Considering left or right connection configuration, detaching the leftmost or rightmost ribbon results in higher power loss compared to other ribbons. Detaching one cell ribbon completely from the string connector results in about 0.2%abs decrease in cell efficiency, while detaching the outer ribbon along all strings of a 120‐half‐cell module results in power loss of about 0.8%. The developed model is validated by performing magnetic field imaging (MFI) measurements, in which the magnetic flux density induced by the current carried by the ribbons is measured.

Experimental and modeling studies of a high-temperature electrochemical hydrogen compressor

Some non-technical factors such as economics and logistics prevent hydrogen (H2) technologies from becoming more widespread in daily life. Today, the prevalence of H2 technologies requires new technological developments. Electrochemical hydrogen compressors (ECHC) are of great interest due to their ability to pressurize and purify in one step. In this study, the electrochemical H2 compression performance of high phosphoric acid (PA) doped poly 2,2-m-phenylene-5,5-benzimidazole (PBI) membrane-based HT-ECHC under high temperature and non-humid conditions was investigated through both an experimental and a numerical approach. The H2 compression capacity of HT-ECHC at different operating voltages was examined by performance tests at 160 °C, and it was determined that the electrochemical compression performance increased with increasing operating voltage. It was observed that the current density values also increased with increasing voltage, and it was determined that a current density of 61.2 A was obtained at 1 V. As a result of the tests, H2 was successfully compressed from atmospheric pressure to 60 bar by HT-ECHC without any gas leakage. The results of the developed model were compared with the experimental performance test data, and the variation of molar flow, cell voltage, and cell efficiency over time was examined. It has been determined that the back diffusion from the cathode to the anode in the cell increases with the increasing operating voltage of HT-ECHC and therefore the cell efficiency decreases. It has been evaluated that the developed model and experimental results are in good agreement.

Numerical analysis of the effect of the evaporator inlet-outlet position on the PV-T performance

The increase in global energy consumption and carbon dioxide emissions increase the interest in renewable energy sources. Solar energy is at the forefront of renewable energy sources, and the decrease in cell efficiency due to various reasons during operation is an obstacle to this technology. Increasing the temperature of photovoltaic cells during operation causes a decrease in cell efficiency. Control of photovoltaic cells temperature is crucial in terms of both prolonging the economic life of the cells and increasing the efficiency of the system. The effect of the evaporator inlet and outlet position of the fluid on the heat transfer is known, but this effect was not examined in the studies carried out to increase the efficiency of the PV-T (photovoltaic–thermal) system. In the current study, the system efficiency parameters and COP (coefficient of performance) values of a PV-T evaporator cooled by forced air circulation were investigated by CFD (computational fluid dynamics) analysis. The analyzes were carried out in a single array for three different flow rates (0.0125 kg/s, 0.0250 kg/s, 0.0500 kg/s) and nine different evaporator inlet-outlet positions (CC, CL, CR, RC, RL, RR, LC, LL, LR), constant radiation of 1000 W/m^2. It was determined that there is a total efficiency difference of over 20% and an overall COP difference of over 25% between the best and worst inlet-outlet positions. The highest total and thermal efficiency were obtained for the RR condition, and the highest electrical efficiency was obtained for the LR condition but in the long-term, the highest efficiency can be achieved with the LC design. In the study also the highest COP values were calculated for the CL condition and the worst COP values for the RR condition.

Time Resolved Measurements of pH in Aqueous Magnesium‐Air Batteries during Discharge and Its Impact for Future Applications

AbstractIn aqueous magnesium air batteries, the influence of the electrochemical behavior on pH of the electrolyte has not been investigated yet, which has a critical effect on the cell performance. We have monitored the evolution of the pH at various discharge current densities in situ in the Mg‐air primary cells, which produce sparingly soluble magnesium hydroxide (Mg(OH)2). These experiments show the temporal evolution of the pH of the electrolyte in the cell discharge, depending on the current density. The pH first increases rapidly to a maximum of pH 11 and then drops down slowly to the equilibrium at pH 10.7. At the peak pH oversaturation of Mg(OH)2 is paramount, leading to the precipitation which balances the Mg(OH)2 concentration in the electrolyte. This precipitation process coats both cathode and anode which leads to a decrease in cell efficiency and voltage. The results show that the cell design of Mg‐air batteries is important for their lifetime and cell performance. The performance of the aqueous magnesium cell is increased several folds when the design is changed to a simple electrolyte flow cell.

Numerical simulation of methanol crossover in flowing electrolyte-direct methanol fuel cell

A two-dimensional, comprehensive model for flowing electrode direct methanol fuel cell (FEDMFC) is developed to investigate cell performance and prevention of methanol crossover. Governing equations consists of the electron and proton transfer equations, mass and momentum conservation equation, energy transfer equations, species transfer of gas and liquid equations, dissolved water equations, as well as modified Tafel equations. The influence of operating parameters (such as flow rate and inlet temperature) and porous properties (such as porosity and permeability) of flowing electrode channel (FEC) on cell performance and methanol crossover are discussed in details. The results show that FEDMFC effectively reduces the methanol crossover rate with no significant reduction of power densities compared with direct methanol fuel cell (DMFC) under the same conditions. The Increase of the FEC flow rate can further reduce the methanol crossover rate. However, a higher flow rate will lead to a decrease in cell efficiency and stability. The FEC flow rate controlled at 1-3 sccm is more appropriate. Additionally, the lower inlet temperature of FEC is associated with lower methanol crossover rate and better cooling effect. The lower porosity is more conducive to reducing the effective diffusion coefficient of methanol, thus decreasing the methanol crossover rate.

Exosomes: Potential Player in Endothelial Dysfunction in Cardiovascular Disease.

Exosomes are spherical bilayer membrane vesicles with an average diameter of 40–100 nm. These particles perform a wide range of biological activities due to their contents, including proteins, nucleic acids, lipids, lncRNA, and miRNA. Exosomes are involved in inflammation induction, oxidative stress and apoptosis, which can be effective in endothelial dysfunction. Due to the induction of mentioned processes in the endothelial cells, the intercellular connections are destroyed, cell permeability increases and finally cell efficiency decreases and functional defects occur. Cardiovascular disease (CVDs) are of consequences of endothelial dysfunction. Thus by identifying the exosome signaling pathways, which induce inflammation, oxidative stress, and apoptosis, endothelial dysfunction and subsequently CVDs can be reduced; exosomes can be used for appropriate target therapy.

Silicon solar cells with nitrogen-rich SiNx/Si interfacial passivation by low-energy nitrogen-ion implantation

We investigated low energy nitrogen ion implantation into the SiNx/Si interfacial layer of silicon solar cells using various energies and fluences, followed by a thermal annealing process. The low energy implanted nitrogen ions penetrated into the SiNx antireflection layer and reached the Si emitter layer. However, ions could not pass through the Ag electrode contact layer and were unable to form the contact passivation layer. A low energy nitrogen ion implanted cell showed the formation of a rich nitrogen layer in the SiNx/Si interfacial area and an increase in electrical performance. With increasing nitrogen ion implantation energy, cells were damaged and suffered decreasing efficiency compared to a reference cell. Increasing the fluence of nitrogen ions also caused a decrease in cell efficiency. After a low temperature annealing process, the cell efficiency recovered almost to the pre-implantation point of the reference cells and showed a similar recovery in their photoreflectance and quantum efficiency. The low-energy nitrogen ion implantation showed the improved cell efficiency of 17.28% for the energy of 12 keV with a fluence of 1 × 1013 cm-2.

Inhibition of Zn dendrite growth using NixZn(1-x)O anodic material during a redox cycling test in Zn/Ni battery

NixZn(1-x)O was used as an anodic material to suppress Zn metal or ZnO dendrite growth on the surface of a Ni-plate electrode in a Zn/Ni redox battery, which can reduce the cell efficiency. ZnO and NixZn(1-x)O nanoparticles were synthesized by a conventional sol-gel method by adding oxalic acid as a chelate agent, and the Zn/Ni cells were fabricated in the following form: Ni(s) | Zn(OH)42−(aq, 0.5 mol), Ni(OH)3−(aq), KOH(aq, 6 M) | Ni(OH)2(s) | Ni(s). The ZnO and Ni0.001Zn0.999O nanoparticles dissolved perfectly in a 6M KOH solution, but the other species did not. When the pure ZnO without Ni2+ ions was used as an anodic material during the redox cycling tests, Zn metal dendrites formed on the negative electrode, but the amount of dendrite formation decreased depending on the concentration of Ni2+. This is possibly because the Ni2+ ions were eluted from the ZnO framework during the redox cycling tests, and the ions possibly played a role as an oxidation catalyst to promote the dissolution of Zn dendrites. On the other hand, excessive Ni2+ ions caused a decrease in cell efficiency due to the growth of K2ZnO2 or K4ZnO3 on the negative electrode. Consequently, Ni0.001Zn0.999O is the most suitable anodic material in a Zn/Ni cell; the cell capacity using the Ni0.001Zn0.999O anodic material was 30.0 mAh.

단결정 실리콘에서 산소농도에 따른 산소석출결함 변화와 태양전지 효율에 미치는 영향

Woongjin Energy Co., Ltd., Daejeon 305-509, Korea(Received November 13, 2014)(Revised November 27, 2014)(Accepted December 5, 2014)Abstract Recent studies have shown methods of improving solar cell efficiency. Especially on single crystalline siliconwafer which is high-efficiency solar cell material that has been widely studied. Interstitial oxygen (Oi) is the main impurityin the Czochralski (Cz) growing method, and excess of this can form precipitates during cell fabrication. We havedemonstrated the effect of Oi impurity and oxygen precipitation concentration of the wafer on Cz-silicon solar cell efficiency.The result showed a decrease in cell efficiency as Oi and oxygen precipitation increase. Moreover, we have found that thecritical point of [Oi] to bring higher cell efficiency is at 14.5 ppma in non-existent Bulk Micro Defect (BMD).Key wordsSolar cells, Efficiency, Czochralski silicon, Oxygen precipitation, BMD

(Invited) Impact of Oxygen-Related Defects on Lifetime Degradation in N-Type CCZ/CZ Mono-Crystalline Silicon during Cell Processing

Although N-type CZ material exhibits a high initial lifetime ideally suited to the fabrication of high efficiency solar cells, degradation of wafer lifetime during processing leading to a decrease in cell efficiency can occur due to the growth of pre-existing small oxygen clusters. The mechanism for lifetime degradation associated with oxygen defects is discussed. Lifetime degradation can be avoided and high cell efficiencies achieved by using wafers with a lower initial oxygen concentration.

High-efficiency photovoltaic technology including thermoelectric generation

Nowadays, photovoltaic solar energy is a clean and reliable source for producing electric power. Most photovoltaic systems have been designed and built up for use in applications with low power requirements. The efficiency of solar cells is quite low, obtaining best results in monocrystalline silicon structures, with an efficiency of about 18%. When temperature rises, photovoltaic cell efficiency decreases, given that the short-circuit current is slightly increased, and the open-circuit voltage, fill factor and power output are reduced. To ensure that this does not affect performance, this paper describes how to interconnect photovoltaic and thermoelectric technology into a single structure. The temperature gradient in the solar panel is used to supply thermoelectric cells, which generate electricity, achieving a positive contribution to the total balance of the complete system.

KrF excimer laser irradiated nanoporous TiO 2 layers for dye-sensitized solar cells: Influence of laser power density

This paper reports the performance of dye-sensitized solar cells (DSSCs) with nanoporous TiO2 photoanodes irradiated by KrF excimer laser beams of various power densities. The laser induces surface remelting and solidification to create textures on the TiO2 layers. After laser irradiation, TiO2 also undergoes a phase transition from anatase to rutile; the amount of the transformed phase increases with the laser power density. For dye-anchored TiO2 layers, light absorption increases first and then decreases as the laser power density increases. The assembled cell efficiency, strongly correlated with the photocurrent density, also increases first and then decreases as the laser power density rises. This indicates that laser treatment creates surface textures on TiO2 that improve light trapping in the dye-anchored TiO2 photoanodes, thereby increasing the photocurrent level and cell efficiency. For high laser irradiation power density, the ablation of the TiO2 layer becomes significant, leading to a decrease in cell efficiency. The surface remelting and solidification process reduces the density of the surface recombination centers on TiO2, resulting in an increase of open-circuit voltage.

High-Efficiency Heterojunction with Intrinsic Thin-Layer Solar Cells: A Review

Heterojunction with intrinsic thin layer (HIT) solar cell has attracted attention of photovoltaic research community due to its low process temperature, as compared to crystalline silicon (c-Si) solar cell and relatively high efficiency (η). In this solar cell structure, thin intrinsic amorphous silicon layers are used as surface passivator, which also acts as buffer layer at the top as well as bottom surfaces of n-type crystalline silicon (c-Si) wafer. A thin p-type a-Si top layer acts as an emitter while highly doped n-type bottom layer is used as a back surface field. There have been suggestions that the device performance comes with significant tunnelling transport of the charge carriers across junction barriers, whereas other investigation suggests that the diffusion of the carriers may be adequate. Various experimental as well as theoretical investigations were carried out to characterize and improve performance of HIT solar cell. For example, it was reported that a thicker p-type emitter (up to 40nm) shows higher open circuit voltage, although short circuit current density (Jsc) and cell efficiency decreases. Recent investigation showed that when the p-type and i-type layer thickness increased (within 4 nm) the open circuit voltage (Voc) as well as the efficiency improves. Using thinner c-Si absorbed is another interesting aspect in which a light trapping scheme can be combined to achieve a better performance characteristics. There has been several theoretical as well as experimental investigations on the use of various types of emitter layer and intrinsic layer of the cell, and their role on the Jsc, Voc, η and fill factor (FF). Investigations of HIT solar cell on p-type c-Si wafers have also been carried out. In this article we will present a brief review on some of the important aspects of the HIT solar cell.

The performance and long-term stability of silicon concentrator solar cells immersed in dielectric liquids

Direct liquid-immersion cooling of concentrator solar cells was proposed as a solution for receiver thermal management of concentrating photovoltaic (CPV) systems. This research investigates the performance and long-term stability of silicon CPV solar cells operated in De-ionized (DI) water, isopropyl alcohol (IPA), dimethyl silicon oil, and ethyl acetate, respectively. Current–voltage characteristics of silicon CPV solar cells are measured. The presence of a thin liquid layer (1.5mm) results in an increase in the silicon CPV solar cells efficiency by 8.5–15.2% from the reference value. With an increase of the liquid layer thickness above the cell surface up to 9mm, due to more incident light is absorbed by the thicker liquid layer, the degree of the improvements to the cell efficiency decreases, which also depends to a noticeable degree on the liquid species. Further, more power output from the cells operated in liquids is achieved under higher concentration ratio. The long-term cell performance is discussed through three separate liquid immersion tests. The results from 1.5mm test demonstrate that degradation of cells performance immersed in IPA and in ethyl acetate mainly occurs by a decrease of Jsc and efficiency during 170days of test. But the long-term organic liquids immersion test (180days) without silicone sealant involved gives confidence of the reliable performance of the silicon CPV solar cells operated in liquids except for DI water. Therefore, the observed performance decay of the cells in 1.5mm test is due to the interaction between the silicone sealant and IPA or ethyl acetate. However, long-term immersion results from 9mm test (100days) show that the stable electrical performance of the cell is difficult to be achieved when immersed in DI water, which is consistent with the previous report.

아연공기전지용 Pr1-x(Sr, Ca)xCoO3양극촉매 제조 및 전기화학적 특성

Zn/Air secondary batteries are high energy density type and environment-friendly. Also, they have safer properties than batteries of other type by low manufacturing cost and using the electrolyte solution. But, they have a weak concerning large output discharge. Oxygen evolution reaction(OER) and oxgen reduction reaction(ORR) in aqueous solution make a result of a decrease of cell efficiency and life span. Therefore, to minimize the voltage drop from between OCV and charge/discharge voltage is key point. The problem should be solved through developing catalysts of high efficiency. In this study, we synthesized powders by citric method and then measured physical characteristics of each powder by XRD, SEM, TGA etc. We examined its electrochemical properties by the cathodic polarization, anodic polarization and cyclic voltammogram. We achieved results that new catalysts showed better performances than existing , , ect. catalysts prepared in our lab.

Parameter setting and analysis of a dynamic tubular SOFC model

An improved one-dimensional dynamic model of a tubular SOFC stack capable of system simulation in the virtual test bed (VTB) simulation environment is presented in this paper. This model is based on the electrochemical and thermal modeling, accounting for the voltage losses and temperature dynamics. The modeling of an external reformer is also included in this study. A detailed parametric analysis of working conditions and cell configuration of the solid oxide fuel cell (SOFC) stack is the main focus of this paper. The following operating parameters are investigated: pressure ratio, temperature, mass flow rate, external reforming degree and stream to carbon (S/C) ratio. The cell geometric parameters studied include cell diameter and cell length. Elevated operating pressure improves the cell performance. Whereas, higher operating temperature decreases both the Nernst potential and the irreversible losses, resulting in an initial increase then a decrease in cell efficiency. It was found that a higher S/C ratio yields a lower H 2 concentration and partial pressure, which has a negative effect on the Nernst potential. Increased cell diameter is found to increase the power due to a larger activation area at the same time and due to longer current path length there is an increase in the ohmic loss. Increased length of the cell has the undesired affect of an increased pressure drop.

A study on swift (∼100 MeV) heavy (Si8+) ion irradiated crystalline Si-solar cell

A study on irradiation (of ∼100MeV, Si-ion) induced degradation effects of crystalline silicon solar cells has been carried out. The cell characteristics show that the cell efficiency decreases to ∼30% (of its pre-irradiated value) after the irradiation (of swift heavy ions of, 1012 or 1013 or 1014ionscm−2 fluences). The reduced efficiency of the irradiated solar cells is recovered back (nearly half of the pre-irradiated efficiency) after annealing at 300°C. The IR spectroscopic studies on the irradiated and annealed solar cells show the presence of di-vacancy and their complexes with impurities like hydrogen, carbon and oxygen. The swift heavy ion irradiation damage in solar cells causing a heavy loss of the cell efficiency has been attributed to these electrically active complexes which shall cause the carrier removal/compensation phenomena for the observed decrease of the cell efficiency. These complexes dissociate on annealing to change their role as donors/acceptors to cause the observed recovery of the cell efficiency on annealing.

Bulk resistivity optimization for low‐bulk‐lifetime silicon solar cells

AbstractGuidelines are presented which are designed to achieve planar solar cell efficiencies as high as 17.5% using existing fabrication technologies and silicon substrates with lifetimes as low as 20 μs. Device simulations are performed to elucidate the need and impact of base doping optimization for different back‐surface passivation schemes, cell thicknesses, emitter profiles, and degrees of dopant–defect interaction. Results indicate that optimal resistivity is a function of back‐surface passivation, with the aluminum back‐surface field (BSF) requiring the highest resistivity, the oxide/nitride stack passivation excelling at an intermediate resistivity, and the ohmic contact needing the lowest resistivity. A comparison of simulated 300 and 100 μm cells shows that thinner cells magnify the differences in optimal resistivity for the three back‐surface passivation schemes. A lifetime model is used to account for dopant–defect interaction that can lower bulk lifetime at higher doping levels. It is demonstrated that cell efficiency decreases and optimal resistivity increases at higher levels of dopant–defect interaction. Simulated devices with an optimized base doping showed an efficiency improvement of as much as 2% (absolute) compared with identical devices with a typical base doping level (1.6 or 1.8 Ω cm) and bulk lifetime of 20 μs. Copyright © 2001 John Wiley & Sons, Ltd.

Characteristics of Silicon Solar Cells Fabricated by Non-Mass-Analyzed Ion Implantation

Silicon solar cells are fabricated by non-mass-analyzed ion implantation using 100% PH3 discharge gas. The energy conversion efficiency of cells fabricated by implantation at 5–10 keV is 10% without anti-reflection coating. Cell efficiency decreases as ion energy or total ion dose is increased. This decrease in cell efficiency is attributed to the detrimental effect of H+ ion. This is mainly because the damage created by co-implanted H+ ions is not completely annealed out.