Cell Performance Parameters Research Articles

Nickel assisted chemical etching for multi-crystalline Si solar cell texturing: a low cost single step alternative to existing methods

The texturing of silicon surfaces is a well-known method of reducing the reflection from the surface of crystalline Si solar cell devices. With the utilization of diamond wires in recent advances in wafer slicing technology, surface texturing for the multi-crystalline Si wafers by the traditional acid-based texturing technique has become difficult. Metal-Assisted Etching (MAE) has been shown to be a promising and low-cost alternative to the traditional acid-based isotropic texturing. This paper reports, for the first time, a new single-step Ni-assisted etching technique to obtain nano-scale porous structures, that is, black silicon on multi-crystalline wafers. We observed lower reflection results in comparison with standard isotropic texturing using a standard acid solution. The structural and optical properties of the surface were identified through reflection measurements and scanning electron microscopy imaging. As a final step, the optimized texturing process was applied to multi-crystalline solar cell devices and showed promising results regarding cell performance parameters.

Thermal management of concentrator photovoltaic systems using microchannel heat sink with nanofluids

A new cooling method for concentrator photovoltaic system is proposed using wide microchannel heat sink with nanofluids. A comprehensive three-dimensional model is developed. The model couples the two-phase (Eulerian-Eulerian) multiphase model for the conjugate heat transfer of nanofluid flow in a wide microchannel heat sink with the thermal model of the concentrator photovoltaic systems. The model is numerically simulated and validated with the available experimental and numerical data. The influences of nanoparticle types, volume fractions, and coolant flow Reynolds number on the solar cell performance parameters are investigated. Results indicate that using SiC-water nanofluids attains lower cell temperature compared with Al2O3-water nanofluids. The increase of nanoparticles volume fraction ratio remarkably reduces the solar cell temperature and enhances the cell temperature uniformity and electrical efficiency. Furthermore, increasing the flow Reynolds number to a specific value significantly enhances the net electrical power. Further increase of the Reynolds number results in a significant reduction in the cell net gained power. By using 4% SiC-water nanofluid, the reduction in maximum local solar cell temperature is ranged between 8 °C and 3 °C compared with pure water with changing the flow Reynolds number from 12.5 to 250 at solar concentration ratio of 20.

Enhanced photovoltaic performance of PEDOT:PSS/Si solar cells using hierarchical light trapping scheme

Organic-inorganic hybrid solar cells have attracted tremendous research attention in recent years owing to their low fabrication cost and potentially high performance. In the present study, hierarchical structures consisting of nanostructures made over micro-textured pyramidal (MPs) silicon surface are used in PEDOT:PSS/Si heterojunction solar cells to achieve a power conversion efficiency (PCE) up to 10.26%. The combined micro-nanostructuring concept provides a superior light trapping ability (compared to only micro-textured Si), mechanical stability (compared to only Si nanowire arrays concept), increased junction area and hence improved photovoltaic (PV) characteristics including short-circuit photocurrent and PCE. Silver assisted electroless wet chemical etching is used to produce nanostructures of different length over the micro-pyramidal Si. The hierarchically structured surfaces have one-fourth reflectance in broad spectral range (300–1100 nm) as compared to micro-pyramidal Si (∼13%) arising from the enhanced light trapping properties of nanostructures owing to multiple interaction of incident light and dimensions equivalent to sub-wavelength structures. Moreover, the hierarchical structures exhibit excellent omnidirectional light trapping ability at wide range of angle of incidence of light and spectral wavelength, which is essential for practical PV applications. This has been demonstrated using solar weighted reflectance corresponding to AM 1.5G solar flux and compared with that of MPs surface. Influence of nanostructuring time on reflectance and PV performance of the solar cell has been investigated. A significant enhancement in PCE up to 0.78% (absolute) and over 8.0% (relative) could be achieved as compared to MPs-Si based hybrid solar cell (control cell) for an optimized hierarchically structured Si surfaces. It is established that an optimal trade-off between reduced reflectance of such surfaces and solar cell performance parameters is essential. Longer nano-structuring despite exhibiting a better light trapping properties results in poor cell efficiency as the nano-structuring also leads to increased surface area and non-conformal coating of the polymer. Hence, increase in photocurrent is also accompanied by a simultaneous deterioration of other cell parameters such as open circuit voltage and fill factor of the device. Nevertheless, a properly designed hierarchical-structured device paves a promising way for developing low-cost and efficient PV applications in the future.

Hybrid Perovskites: Prospects for Concentrator Solar Cells.

Perovskite solar cells have shown a meteoric rise of power conversion efficiency and a steady pace of improvements in their stability of operation. Such rapid progress has triggered research into approaches that can boost efficiencies beyond the Shockley–Queisser limit stipulated for a single‐junction cell under normal solar illumination conditions. The tandem solar cell architecture is one concept here that has recently been successfully implemented. However, the approach of solar concentration has not been sufficiently explored so far for perovskite photovoltaics, despite its frequent use in the area of inorganic semiconductor solar cells. Here, the prospects of hybrid perovskites are assessed for use in concentrator solar cells. Solar cell performance parameters are theoretically predicted as a function of solar concentration levels, based on representative assumptions of charge‐carrier recombination and extraction rates in the device. It is demonstrated that perovskite solar cells can fundamentally exhibit appreciably higher energy‐conversion efficiencies under solar concentration, where they are able to exceed the Shockley–Queisser limit and exhibit strongly elevated open‐circuit voltages. It is therefore concluded that sufficient material and device stability under increased illumination levels will be the only significant challenge to perovskite concentrator solar cell applications.

Effect of Electrolyte on High Sulfur Loading Li-S Batteries

Practical lithium-sulfur batteries require high sulfur electrode loading and lean electrolyte designs, which entail more research efforts on the two cell-design parameters - sulfur loading and electrolyte/sulfur loading ratio (E/S). In this work, a systematic investigation is performed to understand the impact of these two variables over key Li-S cell performance parameters. It is demonstrated that Li-S cells’ power performance strongly depends on the E/S ratio, while both E/S ratio and sulfur loading significantly influence the cycle life of Li-S cells. Low E/S ratio and high sulfur loading both give rise to fast lithium anode corrosion, which induces fast capacity fade and Coulombic efficiency decay. Pre-passivation of the lithium anode with an ionic conductor Li3PO4 protection layer only improves the Coulombic efficiency retention at sulfur loading levels much lower than the practical threshold. Meanwhile, increasing the concentration of LiNO3 additive in the electrolyte is found effective in sustaining the cycling capacity and the Coulombic efficiency over a reasonable usage window (∼200 cycles). The role of LiNO3 is the protection of lithium anode during cycling.

Insights Into the Microscopic and Degradation Processes in Hybrid Perovskite Solar Cells Using Noise Spectroscopy

We report a clear correlation of the features observed in photocurrent noise‐fluctuations to the performance parameters of hybrid perovskite solar cells. The general trend of increasing noise amplitude which spreads over a wider range of frequency as a function of aging is established. High‐resolution spatial mapping of the photocurrent in typical devices and the associated variation of the noise spectrum confirms the underlying trend.

SOFC single cells fed by biogas: Experimental tests with trace contaminants

Biogas from biological treatments and from the waste degradation in landfills generally contains a wide range of trace impurities (e.g., sulphur compounds, siloxanes, halogens, tar compounds, etc.). This paper describes an experimental analysis performed with SOFC single cells fed by a synthetic gas polluted by H2S, HCl, D4 and a mixture of H2S + C2Cl4. The aim is to detect the threshold tolerance limit on different cell performance parameters. Results show how: hydrogen sulphide has a strong impact on the polarization losses due to the nickel sulphide formation on the electrode that causes a mass transfer resistance. Hydrogen chloride particularly limited the electrochemical processes. Octamethylcyclotetrasiloxane (D4) showed a high impact on SOFC performance even at ultra-low level (78–178 ppb(v)) as a consequence of the formation of silicon dioxide covering the anode porous sites. Sulphur added to C2Cl4, accelerated the deterioration of SOFC performance. In addition, current density variations and operating temperature are studied during sulphur poisoning. An opposite behaviour on SOFC performance was revealed by operating temperature and current density.

Systematic characterization of the effect of Ag@TiO2 nanoparticles on the performance of plasmonic dye-sensitized solar cells

The use of plasmonic nanoparticles (NPs) in dye-sensitized solar cells (DSSCs) in an effort to enhance their power conversion efficiencies (PCEs) increases light absorbance of the cells but also affect their electron dynamics. This has contributed to the failure of plasmonic NPs to make the expected high impact of PCE enhancement. Herein, we investigated the wide range effects of plasmonic NPs on the performance of DSSCs, using extended characterization and a systematic approach. We prepared DSSCs using Ag@TiO2 NPs-doped TiO2 photoanodes. Using a wide range doping concentration, we obtained panchromatic enhancement effect with two optimal doping concentrations (0.1 and 1 wt. %).They enhanced PCE via mainly: a) optimal band alignment for efficient charge injection; and b) a balance of the negative and positive effects of plasmonic NPs on cell performance parameters (open circuit voltage, fill factor, charge transfer resistance against recombination, electron life time and charge collection efficiency); respectively. The PCE of the pristine sample increased from 4.66 to 4.88 and 5.00% via these 2 routes, respectively. The major cause of not obtaining very high PCE was charge recombination from high charge density. Thus, these observations might serve as invaluable guidance for the preparation of highly efficient plasmonic DSSCs.

Rapid development in two-dimensional layered perovskite materials and their application in solar cells

Two-dimensional (2D) layered organic-inorganic hybrid perovskite (2D PVK) materials have been recently developed as a novel candidate for photovoltaic application with high stability and a maximum power conversion efficiency of 12.5%. This article summarized these newly emerging 2D PVK materials and their uses in solar cells. The structural, physical, and chemical properties as well as the classification of 2D PVK materials are discussed. The photovoltaic performance parameters of various 2D perovskite solar cells (2D PSCs) are summarized and their device stability is compared with conventional 3D perovskite solar cells (3D PSCs). It has been concluded that 2D PVKs show greater stability upon humidity, heat stress, and light intensity as compared to 3D analogues and act as a class of promising materials for application in solar cells.

Identifying the Cause of Voltage and Fill Factor Losses in Perovskite Solar Cells by Using Luminescence Measurements

AbstractThe open‐circuit voltage (VOC) and fill factor are key performance parameters of solar cells, and understanding the underlying mechanisms that limit these parameters in real devices is critical to their optimization. Device modeling is combined with luminescence and cell current–voltage (I–V) measurements to show that carrier transport limitations within the cell can significantly reduce the cell voltage around the maximum power point as well as, under certain conditions, at VOC. An important consequence is that the cell terminal voltage cannot be assumed a priori to be only limited by parasitic recombination. It is demonstrated that luminescence‐based measurements can be used to reconstruct cell I–V curves with removal of any transport limitation effects, which allows the contribution of recombination, shunt resistance, and series resistance on the fill factor to be clarified. Such luminescence‐based measurements allow the contactless characterization of cells and cell precursor structures, and should prove highly valuable as a diagnostic tool for the development of new cell structures and large‐area cells.

Rhodanine side-chained thiophene and indacenodithiophene copolymer for solar cell applications

In this work, 2-(3-ethyl-4-oxothiazolidin-2-ylidene)malononitrile is connected on the β position of thiophene, and this monomer is copolymerized with indacenodithiophene (IDT) to build one novel photovoltaic polymer (PIDTPCR). The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) level of the polymer is −5.26 eV and −3.45 eV, respectively. Compared with reference polymer without rhodanine side chain, PIDTPCR polymer shows low band gap and low energy level which contribute to the Jsc and Voc of the PSCs devices. The best performance parameters of the solar cells devices are Voc (0.91 V), Jsc (10.1 mA/cm2), FF (52.4%) and PCE (5.18%).

Superior silicon surface passivation in HIT solar cells by optimizing a-SiOx:H thin films: A compact intrinsic passivation layer

Abstract The microstructure of the intrinsic amorphous silicon oxide (i-a-SiO x :H) thin films is the key for crystalline silicon surface passivation in high-performance HIT solar cells. Understanding and subsequently optimizing the i-a-SiO x :H microstructure is essential in improving defect passivation and carrier transportation in a-SiO x :H films. In this work, we investigate the relationship between the bulk microstructure of i-a-SiO x :H thin films at different oxygen content and the passivation quality of the silicon surface. The results revealed that, as the oxygen content increases, the dominating growth mechanism of i-a-SiO x :H films changes. Consequently, the component contents of i-a-SiO x :H thin films were varied and the microstructure showed a first improved and then deteriorated trend with increasing oxygen content. A compact, less-defective and ordered microstructure of the a-SiO x :H film can only be obtained when there comes a tradeoff between Si O and Si H(Si 3 ) bonding formation. Correspondingly, the improved defect passivation and the enhanced carrier transportation in a-SiO x :H films lead to the increase of V oc , FF and QE of HIT solar cells, all of which are key solar cell performance parameters.

Control of the microstructure of SnS photovoltaic absorber using a seed layer and its impact on the solar cell performance

Abstract SnS thin films were prepared by sulfurizing a sputtered metallic Sn precursor film deposited on a Mo-coated sodalime glass substrate. Some of the precursors were deposited on a thin e-beam evaporated SnS seed layer with a 100–300 nm thickness and the effects of the seed layer on the sulfurization reaction were investigated. The seed layer provided nucleation sites for SnS crystals during the sulfurization and promoted a (040) preferred orientation, whereas a strong (101) orientation was observed in the non-seeded SnS absorber films. In addition, with introduction of the seed layer, the columnar grains observed in the non-seeded SnS film were transformed to an equiaxed grain structure with many grain boundaries. The SnS thin films with (040) preferential orientation and equiaxed crystal structure contributed not only to improvement of solar cell performance parameters, but also to ensuring uniformity between samples. This is considered to be related to the three-dimensional arrangement of the interlayer existing in the SnS unit cell having a very long b axis.

Current R&D status of thermochemical water splitting iodine-sulfur process in Japan Atomic Energy Agency

Current R&D on the thermochemical water splitting iodine-sulfur (IS) process in Japan Atomic Energy Agency (JAEA) is summarized. Reactors were fabricated with industrial materials and verified by test operations: a Bunsen reactor, a H2SO4 decomposer, and a HI decomposer. Component materials of the reactors were stable in the operation environment. Small amount of H2SO4 in the anolyte solution in an electro-electrodialysis (EED) cell had no negative impact on cell performance parameters. Relationship between cell solution composition and temperature and cell parameters was formulated by experimental data. Demonstration of the test facility with process design of 100 L/h hydrogen production is performed to verify integrity of process components and stability of hydrogen production. Tests of sections were first conducted individually to show material processing rates were controllable. Based on the result, an 8-h continuous operation of the total IS process was performed in February 2016 with H2 production rate of 10 L/h. Demonstrations are planned for longer operation period and higher H2 production rate after improvement of components to prevent troubles.

Impact of front-side point contact/passivation geometry on thin-film solar cell performance

In this work, we perform an extensive campaign of three-dimensional numerical simulations of CIGS solar cell structures to investigate the effect of a surface-passivated CIGS with point contacts openings on the cell performance parameters (Jsc, Voc, FF and η). Detailed analysis of the combination of passivation thickness, point contact size and pitch is performed under the hypothesis of highly defective CIGS front surface and ideal chemical passivation: efficiencies close to the case of ideal (i.e., defect-free) CdS/CIGS interface can be achieved by optimized nanometer-scale point contact arrays. To account for field-effect passivation due to positive residual charge density, Qf, within the passivation layer, we vary Qf in the range 1010–1013cm−2 under the two extreme scenarios of ideal or ineffective chemical passivation. Several examples of CIGS cells with different buffer layers (CdS, ZnO, ZnMgO, In2S3, Zn(O, S)) are also analyzed. We find that a positive Qf in the interval 1012– 5·1012cm−2 can help completely recover the ideal cell efficiency, irrespective of the chemical passivation effect and even in the presence of unfavorable conduction band alignment at the buffer/CIGS heterojunction. This may help devising solutions with buffer materials alternative to CdS, boosting the performance of otherwise surface-limited cells. The effect of grain boundary defect density and position with respect to point contacts is also addressed, with a grain dimension of 750nm.

Cadmium free high efficiency Cu2ZnSn(S,Se)4 solar cell with Zn1−xSnxOy buffer layer

We have investigated the simulation approach of a one-dimensional online simulator named A Device Emulation Program and Tool (ADEPT2.1) and the device performances of a thin film solar cell based on Cu2ZnSn(S,Se)4(CZTSSe) absorber have been measured. Initiating with a thin film photovoltaic device structure consisting of n-ZnO:Al/i-ZnO/Zn1-xSnxOy(ZTO)/CZTSSe/Mo/SLG stack, a graded space charge region (SCR) and an inverted surface layer (ISL) were inserted between the buffer and the absorber. The cadmium (Cd) free ZTO buffer, a competitive substitute to the CdS buffer, significantly contributes to improve the open-circuit voltage, Voc without deteriorating the short-circuit current density, Jsc. The optimized solar cell performance parameters including Voc, Jsc, fill factor (FF), and efficiency (η) were calculated from the current density-voltage curve, also known as J–V characteristic curve. The FF was determined as 73.17%, which in turns, yields a higher energy conversion efficiency of 14.09%.

ZnO nanoparticles with different concentrations inside organic solar cell active layer

In the present work, ZnO nanoparticles (NPs) have been dispersed alone in the same solvent of the active layer for improving performance parameters of the organic solar cells. Different concentrations of the ZnO NPs have been blended inside active layer of the solar cell based on poly(3-hexylthiophene) (P3HT), which forms the hole-transport network, and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), which forms the electron-transport network. In the present investigations, the ZnO NPs may represent an efficient tool for improving light harvesting through light scattering inside active layer, electron mobility, and electron acceptance strength which tend to improve photocurrent and performance parameters of the investigated solar cell. The fill factor (FF) of the ZnO-doped solar cell increases nearly 14% compared to the non-doped solar cell when the doping is 50%. The present investigations show that ZnO NPs improve power conversion efficiency of the solar cell from 1.23% to 1.64% with increment around 25% that takes place after incorporation of 40% as a volume ratio of the ZnO NPs inside P3HT:PCBM active layer.

Ex situ and in situ sensitized quantum dot solar cells

Although quantum dot‐sensitized solar cells (QDSCs) prepared with in situ sensitized wide‐band gap semiconductor nanorods are commonly reported, very few examples of the ex situ sensitization of these nanorods are known. They usually result in poor solar cell performance parameters. In this work, we have tested the photovoltaic application of both ex situ and in situ sensitized ZnO nanorods by linker‐assisted attachment and by the successive ionic layer adsorption and reaction (SILAR) technique, respectively. For the ex situ sensitization, instead of classical spherical QDs, we used quasi two‐dimensional CdSe nanoplatelets (NPLs) of controlled thicknesses, the photovoltaic application of which has never been reported before. Regarding the in situ sensitization, the photoanodes were characterized by XRD, UV–VIS absorption, and Raman spectroscopy during deposition, which helped to better understand the formation of CdSe QDs nanostructured ZnO surface. Devices incorporating in situ sensitized ZnO nanorods demonstrated superior performance compared to the best measured efficiencies of QDSCs prepared with ex situ sensitization, and their J–V characteristics were more reproducible.

Effects of Temperature and Concentration Mono and Polycrystalline Silicon Solar Cells: Extraction Parameters

The simple and efficient method for the extraction of all the parameters of a solar cell from a single current-voltage curve under one constant illumination level based on the Lambert W function. On calculating the lsqcurvefit function with constraints, between the experimental current-voltage characteristic and a theoretical arbitrary characteristic based on Lambert W-function. It is significant to understand the effect of the light intensity and temperature on output performance of the crystalline solar cells. The effect of light intensity and temperature on performance parameters of mc-si and pc-si solar cells is discusses. The experiments have been carried out under a solar simulator for various intensity levels in the range 1-2.5 sun and 25-60°C, respectively. The experiment was carried out employing solar cell simulator with varying cell temperature at constant light intensity. The results show that cell temperature has a significant effect on the photovoltaic parameters and it controls the quality and performance of the solar cell. The maximum power and efficiency are found to be decreased with cell temperature and the temperature coefficient of the efficiency and maximum output power is found to be negative.

Quantitative local current-voltage analysis and calculation of performance parameters of single solar cells in modules

Quantitative characterization of single cells already embedded in modules is performed by a combination of electroluminescence imaging and dark lock-in thermography. Electroluminescence imaging is used to determine the terminal voltages of single cells in modules, and dark lock-in thermography imaging enables the use of quantitative analyses of single solar cells with the software Local I-V 2. This combination yields spatially resolved images of the performance parameters of single cells. To check the reliability of the method also the directly measured voltages of the single cells in a module have been used for Local I-V evaluation and are compared to the results of Local I-V evaluation from voltages determined by EL. The accuracy of the voltage determination in our experiments is about ±1% compared to directly measured voltages, leading to an accuracy of the cell parameters such as J01, Uoc, efficiency, power, FF, and so on of about ±2% using the voltages determined by EL for the Local I-V analysis. With the method introduced it is possible to quantitatively identify the performance of single solar cells in modules reliably and non-destructively, thereby tracking quantitative changes of the cell performance due to degradation processes with high sensitivity and spatial resolution becomes possible.