12 research outputs found
Single Step Inverted Pyramid Texturing of n-type Silicon by Copper Assisted Chemical Etching
No full textIn this paper, we present the results of the study on the fabrication of inverted pyramids on n-type Si wafer by a single-step anisotropic copper-assisted chemical etching. The relationship between etchant composition, etching time and the surface morphology for n-type Si has been investigated. Different surface structures were obtained by adjusting molarity of H2O2, Cu(NO3)(2), HF in the etching solution. Cu(NO3)(2) amount promoted, while increasing H2O2 amount over optimum value reduced the etch rate. By optimizing etching duration, etching temperature and etchant composition, uniform distribution of inverted pyramids with dimensions around 2 mu m was achieved. Surface average weighted reflectance was reduced to 5.67% in the wavelength range of 400-1000 nm with novel surface texturing method
Freestanding and supported processing of sub-70 μm kerfless epitaxial Si and thinned Cz/FZ Si foils into solar cells: An overview of recent progress and challenges
No full textsponsorship: The authors gratefully acknowledge the efforts of several people who were involved in this work over the last few years, namely Jonathan Govaerts, Stefano Granata, Menglei Xu, Ergi Donercark, Ivan Sharlandshiev, Shashi Kiran Jonnak, Shruti Jambaldinni, Robert Roozeman, Jarkko Heildcinen, Thomas Kaden, Zuzana Kovacova, Erich Neubauer, Michael Grimm and Kaori Nagaoka. The authors also acknowledge the funding received for this work from the European Commission for the H2020 project CABRISS under grant agreement No. 641972. Imec is a partner in EnergyVille (www.energyville.be), a collaboration between the Flemish research partners KU Leuven, VITO, imec, and UHasselt in the field of sustainable energy and intelligent energy systems. (European Commission|641972, H2020 Societal Challenges Programme|641972)status: Publishe
Spreading Resistance Modeling for Contact Resistivity Extraction in Ohmic Multilayer Structures With Circular Electrodes
No full textContacts featuring multiple layers of materials in combination with metal electrodes enabled record-high power conversion efficiencies for solar cells in recent years. Minimizing the contact resistivity in these multilayer structures is critical to achieve a high device performance and rapid characterization methods are crucial for the experimental analysis of this aspect. However, commonly used test methods and the associated mathematical formulations to extract contact resistivity are not designed for samples with multiple layers. In this work, we analyze formulations describing the resistance measured in ohmic multilayer test structures, which are used to fit and extract an unknown contact resistivity. We focus on a contacting scheme with circular electrodes, commonly named after Cox and Strack (CS), and analyze a material configuration consisting of a thick Si substrate fully coated with a thin conductive layer (CL). We demonstrate the applicability and accuracy of various spreading resistance models (SRMs) from the literature to calculate the measured resistance and compare the results with those obtained by the finite element method (FEM). Moreover, we present a new SRM with a closed-form expression for the measured resistance, which is computationally more efficient than the existing SRMs. Last, we demonstrate the applicability of this model in experiments with (n)c-Si/(i)a-Si:H/(n)a-Si:H/indium tin oxide (ITO) test structures
Spreading resistance modeling for rapid extraction of contact resistivity with a four-point probe
No full textExtraction of contact resistivity (ρc) with the four-point probe (4PP) method requires considerably fewer fabrication and measurement steps compared to conventional alternatives (e.g. the transfer length method, TLM). Yet, the method is rarely used, mainly due to the requirement of 3D simulations used in the data fitting procedure. Moreover, a work analyzing the details of the method, which can provide a quantitative guideline to the users, is lacking in the literature. In this work, we show that the 3D simulations can be replaced with a spreading resistance model (SRM) implemented in a numerical calculation platform (e.g. MATLAB). Using the SRM, we achieve drastically short calculation durations (<1 s) compared to durations of 3D simulations based on the finite element method. We show that the resolution and reliability of the extracted ρc depends critically on geometrical and electrical parameters of the system, such as the probe tip spacing and sheet resistances of the layers. We also present an alternative measurement procedure that is fully based on 4PP measurements of only one substrate, which eliminates the need for an eddy-current measurement or an additional set of dedicated samples. We demonstrate the viability of the 4PP method in experiments by comparing the results with those obtained by the TLM, for ρc between 5 × 10−3 to 1 × 100 Ω cm2. Lastly, we provide a free software that can execute the calculations discussed herein
Enhanced Passivation Properties of a-Si:H and Reactive ITO Sputtering for SHJ Solar Cells
No full textEnhancement of the conversion efficiency of silicon solar cells is crucial for the improvement of renewable electricity resources. The device properties such as minority carrier lifetime, series resistance, contact resistance and optical properties should be improved simultaneously to achieve higher photo conversion efficiencies. We use industry compatible processes flow to fabricate large-area silicon heterojunction (SHJ) solar cells combined with reactive ITO sputtering. The passivation properties of a-Si:H layer was improved by hydrogen plasma treatment resulting in a lower interface defect density and higher "H" content in the deposited thin a-Si:H layer. Moreover, carrier density, mobility and resistivity of ITO layer was analyzed and the best deposition condition of ITO is integrated to SHJ solar cell process sequence. Contact resistivity between ITO and low temperature silver paste was decreased by optimized drying and curing temperature parameters. In large- area SHJ solar cell, we have achieved conversion efficiency of 20.8%
A Study on Tetragonal-star Like Shaped Inverted Pyramid Texturing
No full textSurface texturing is one of the key process steps in solar cell fabrication. For an ideal surface texturing, surface recombination should be kept as low as possible while the light trapping property is improved. The formation of a random inverted pyramids is a good candidate with its improved light trapping properties compared to standard upright pyramid texturing and its reduced surface roughness compared to nanowire texturing resulting in reduced surface recombination velocity. In this work, we investigate a single step, lithography-free, Cu-assisted inverted pyramid texturing resulting in significantly reduced surface reflection on p-type Cz-Si. With the help of randomly distributed star-shaped inverted pyramid texturing on p-type Si, the weighted average reflection was reduced to 3% for p-type Si between 400-1000 nm. As a first cell trial, standard Al-BSF cells were fabricated using industrial process tools on p-wafer with star-shaped IPs. The low-cost, effective and repeatable nature of the developed single-step etching process has a high potential to replace surface texturing steps in the large-scale solar cell production cycle. Due to the implantation of star-shaped inverted pyramids to Al-BSF Si solar cell fabrication, short circuit current density was improved by more than 3.5%, resulting in 39.1mA/cm(2)
Silica aerogel as rear reflector in silicon heterojunction solar cells for improved infrared response
No full textSilicon (Si), with its indirect bandgap, is a non-ideal absorber. Thus, various strategies to boost silicon solar cells' efficiency, including advanced texturing, multilayer anti-reflecting coating, and rear reflectors are utilized. Dielectrics, deposited at elevated temperatures under a vacuum environment, are currently used to reduce the parasitic metal absorption at the rear. This work demonstrates that solution-based silica aerogel thin film is a flawless candidate for rear reflectors due to cost-effective deposition and near unity refractive index. We demonstrate that the morphology of aerogel thin films, spin-coated at room temperature under an ambient atmosphere, can be controlled by altering the solution concentration and spin-coating speed. We demonstrate -0.25 mA cm-2 short-circuit current density gain in the near-infrared region compared to cells with optimized indium zirconium oxide rear reflectors. Additionally, we show that incorporating aerogel in silicon heterojunction solar cells reduces the overall indium consumption required for TCO by more than 50%.PV-LA
Impact of oxygen partial pressure during Indium Tin Oxide sputtering on the performance of silicon heterojunction solar cells
No full text© 2022 Elsevier B.V.TCO has multiple functions in SHJ solar cell design, including the lateral transport of the photogenerated current and also providing high transparency and anti-reflective behavior. While superior performance lies behind concurrently addressing its multi-functions. Hence the balance between the optical and electronic properties of TCOs need careful engineering. In this study, RF sputtered Indium Tin Oxide films are analyzed in terms of their optical and electrical properties. The variations in the resistivity, mobility, carrier concentration, and specific contact resistivity of the film concerning oxygen partial pressure are discussed. Specific contact resistivity value for screen-printed low-temperature Ag contacts is decreased down to 0.4mΩ.cm2. The total increment on short-circuit current density is 0.6 mA/cm2 by reactive ITO sputtering. The photoconversion efficiency values of SHJ cells fabricated on 170 cm2 area with reactive sputtering is 20.56%, and optical loss analysis is carried out for the SHJ solar cells to quantify the performance of solar cells
Interface and material properties of wide band gap a-SiCx:H thin films for solar cell applications
No full text© 2021 Elsevier LtdA thin intrinsic hydrogenated amorphous silicon carbide ((i) a-SiCx:H) layer with a wide band gap attracts attention as an alternative passivation layer instead of intrinsic hydrogenated amorphous silicon ((i) a-Si:H) for heterojunction photovoltaic applications. The optical band gap of (i) a-SiCx:H can be widened up to 2.24eV. An increase in the optical band gap makes this layer appropriate as the window material by reducing the parasitic absorption. However, the deposition regime should be investigated to understand the incorporation of carbon. The influence of several deposition parameters such as precursor gasses flow rates and plasma power density on the (i) a-SiCx:H layers were investigated in optical, electrical, and elemental aspects. Relatively high interface trap densities were detected related to carbon piling up at the interface. An increase in the amount of C in the interface affected the passivation quality and fixed charge density of the layer. The ratio of secondary ion intensities measured by time of flight-secondary ion mass spectroscopy presents general hydrogen filling of possible dangling bonds and the bonding preferentiality between the silicon or carbon atoms. The passivation quality of the (i) a-SiCx:H layer partially enhanced by stack layer deposition of (i) a-Si:H/(i) a-SiCx:H resulting effective lifetime above 100 μs
Seiðr, kunnosta, fjölkyngi. Le parole della magia nelle prime saghe della Heimskringla
No full textThis article aims to point out those narrative and lexical elements that, in the first sagas of Snorri’s Heimskringla, relate to magic and the use of magic. In the Nordic world, magic was strictly connected to ancient pagan beliefs; for this reason, magic elements are more common in those sagas settled in a pagan environment. Nevertheless, the pagan rituals and cult are never openly described, because the sagas were written in a Christian and Christianised context. Their author was not interested in conveying the old deviate belief of Paganism to his contemporaries, but only in narrating the heroic past of Norwegian kings. In the Sagas, thus, pagan cults are regarded as mere mistakes, due to the kings’ naiveté. Paganism could not possibly undermine the kings’ noble progeny, which included, among others, Olaf the Saint. This is the reason why many of the magic aspects in the Sagas are related to foreign, non Scandinavian, characters, especially Sámi. They are described as wise and fearsome at the same time, expert in seiðr, that is, magic stricto sensu. They possess superior knowledge, which, however, is not a merit, being, on the contrary, what characterizes them in a negative way. The art of seidr, in fact, though symptomatic of their knowledge, is a devious art, connected to vicious and lascivious behaviours (ergi). The episodes about magic arts recounted in the Sagas reveal aspects typical of Sámi’s shamanism. It is quite likely that such shamanic rituals were not only typical of Sami people but also of Scandinavians. This is, however, not testified in the Sagas, which reject any
Scandinavian connection with magic, pushing the magic practices beyond the Scandinavian borders and attributing them to foreign peoples
