1,721,060 research outputs found
Localized metal plating on aluminum back side PV cells
No full textIn this work we demonstrate a new selective metallization technique to perform localized plating on the screen-printed Al contact using the innovative approach based on Dynamic Liquid Drop/Meniscus that is able to touch the cell back contact in specific defined positions and show that it is possible to produce suitable electrical and mechanical contact with Al-Si and thus to replace the silver from the back contact in the cell manufacturing process reducing the solar cell cost. A fast pre-treatment process was developed to clean and prepare the surface of the aluminum on the back side of PV cells allowing direct plating with good electrical contact. Several commercial aluminum screen printable pastes have been experimented also having different distribution of sphere particles dimensions. We have used high resolution Scanning Electron Microscopy (SEM) and compositional microanalysis with Energy Dispersive X-Ray microanalysis (EDX) to evaluate the metal dispersion within aluminum-silicon inter-diffused region and Transfer Length Method and current-voltage measurements to estimate the specific contact resistivity of the metal contact and series resistance of the overall solar cell device. We have found that the interconnection ribbon soldered on tin contacts plated on screen printed aluminum back contact shows adhesion higher (> 1N/mm) than that verified on screen printed silver over silicon. The main difference between a tin pad and a nickel-tin pad will be shown. Efficiency increase and fill factor are compared respect standard Al-Ag back contact PV cell
Collection efficiency at near-bandgap wavelengths in actual Si solar cells
No full textAn expression for collection efficiency in actual Si solar cells is derived from the expression of Basore for inverse quantum efficiency vs. absorption depth at near-bandgap wavelengths. In the new expression, only internal rear-surface reflectance is an adjustable parameter. The new expression is used in reported actual Si solar cells, where it is compared to different approaches to evaluate collection efficiency including the linear fitting to inverse internal quantum efficiency versus absorption depth. This allows showing experimentally that these approaches are more liable to errors than the proposed expression for collection efficiency. © 2018 Author(s)
Porous silicon technology, a breakthrough for silicon photonics: From packaging to monolithic integration
No full textLow cost concept based on the porous silicon technology is shown to be well suitable for integrating monolithically the photonic devices on a standard silicon wafers by using localized SOI structures fabricated by electrochemical anodization of silicon wafers followed by thermal oxidation of porous silicon. The new approach consists in realizing buried localized porous oxidized silicon by exploiting two different routes: n- epi/n+/n- structures on p-type wafers and ionimplantation on standard CMOS/BiCMOS wafers. The peculiarities of the developed approach, including anodization and thermal oxidation regimes to form oxidized porous silicon regions with the required properties are presented. The advantages of the proposed approach in realizing the fiber-to-chip and power-over-fiber coupling are discussed
Saturation current as a function of sheet resistance in Si
No full textWe present the exact analytical solution to minority-carrier transport in the dark for non-uniformly doped Si regions in low-level injection, where bulk lifetime is inversely proportional to the square of doping density according to the Dziewior and Schmid model of Auger recombination and diffusivity is constant. The relevant expression for emitter saturation current density, J0em, can be set as a function of sheet resistance, RSHEET. Reported measured J0em(RSHEET)-curves in n- and p-type metal-coated emitters are matched by the presented J0em(RSHEET)-expression. To this aim, reported doping functions for band-gap narrowing are set as functions of RSHEET. The application range of the presented solution is checked. © 2018 Author(s)
Simple modeling of intrinsic bulk lifetime in doped silicon
No full textBased on the data in the literature, in highly-doped Si, where Auger recombination predominates, one can observe that, while minority-carrier bulk lifetime is inversely proportional to the square of doping density, diffusivity can be taken as constant. This implies that, at high dopings, diffusion length can be considered as proportional to the reciprocal of doping density. In the present work, we assume that such a dependence of diffusion length on doping holds at lower dopings as well, in the case, where Auger recombination prevails. This allows deriving a very simple expression for Auger lifetime as a function of diffusivity that is used together with a reported expression for radiative lifetime to calculate intrinsic lifetime at all dopings. The new expression for intrinsic lifetime is consistent with reported doping functions for minority-carrier diffusivity and agrees with the data of lifetime for dopings higher than 4×1017 cm-3 in both p-type Si and n-type Si. We exploit the relevant theory to show that such results are due to the fact that, at those doping levels, both diffusivity and Auger recombination are enhanced by electron-hole interaction. © 2018 Author(s)
Porous silicon solar cells
No full textWe developed a new process for the fabrication of crystalline solar cell, based on an ultrathin silicon membrane, taking advantage of porous silicon technology. The suggested architecture allows the costs reduction of silicon based solar cell reusing the same wafer to produce a great number of membranes. The architectures combines the efficiency of crystalline silicon solar cell, with the great absorption of porous silicon, and with a more efficient way to use the material. The new process faces the main challenge to achieve an effective and not expensive passivation of the porous silicon surface, in order to achieve an efficient photovoltaic device. At the same time the process suggests a smart way to selective doping of the macroporous silicon layers despite the through-going pores. © 2015 IEEE
Electroplated contacts and porous silicon for silicon based solar cells applications
No full textIn this paper, a two-layer metallization for silicon based solar cells is presented. The metallization consists of thin nickel barrier and thick copper conductive layers, both obtained by electrodeposition technique suitable for phosphorus-doped 70-90 Ω/sq solar cell emitter formed on p-type silicon substrate. To ensure the adhesion between metal contact and emitter a very thin layer of mesoporous silicon is introduced on the emitter surface before metal deposition. This approach allows metal anchoring inside pores and improves silicon-nickel interface uniformity. Optimization of metal contact parameters is achieved varying the anodization and electrodeposition conditions. Characterization of contacts between metal and emitter is carried out by scanning electron microscopy, specific contact resistance and current-voltage measurements. Mechanical strength of nickel-copper contacts is evaluated by the peel test. Adhesion strength of more than 4.5 N/mm and contact resistance of 350 μΩ cm2 on 80 Ω/sq emitter are achieved. © 2015 Elsevier B.V. All rights reserved
Aluminum-silicon interdiffusion in screen printed metal contacts for silicon based solar cells applications
No full textIn this work we propose a detailed investigation of the Al - Si interdiffusion that occurs during the firing process of the Al-Si back contact of silicon based solar cells. The investigation is based on high resolution scanning electron microscopy (SEM) and compositional microanalysis with energy dispersive X-Ray microanalysis (EDX). We have found a dependence of Si precipitation in the Al matrix depending on the microstructure of the Al screen printable paste. We suggest a gettering effect promoted by the larger Al particles lying within the Al paste being able to affect the Al paste resistivity, the Al distribution within the BSF region of the solar cell, thus affecting the solar cell performances and finally the Al paste thermal expansion coefficient. Finally we demonstrate that the presence of the glass frit reduces the surface tension and, homogenizes the diffusion process. Reduction of surface tension decreases the internal pressure and increases the Si interdiffusion in Al. © 2013 The Authors
New selective processing technique for solar cells
No full textA new selective processing technique based on a confined dynamic liquid drop\meniscus is presented. This approach is based on localized wet treatment of silicon wafers using confined and dynamic liquid drop that while in contact with the wafer forms a dynamic liquid meniscus. Such new technique allows to touch in specific defined positions the silicon wafer (front and/or back) in order to perform any kind of wet processing without the need of protective photo-resist. The new selective processing technique allows the metallizations (front and back) of mono and multi crystalline silicon solar cells. The front grid contacts are obtained by locally etching the silicon nitride, forming in a thin layer of meso-porous silicon and totally filling the meso-porous layer by pulse reverse plating a Nickel film. Copper and Tin are then electroplated using the same selective processing. This technology provides an effective solution to avoid silver pastes for front contact grid, as it guarantees low specific contact resistivity (550 μΩcm2 on a 75 Ω/□ n-type doped emitter) and good adhesion to the silicon substrate (i.e. greater than 550 g/mm). The Al back side of the solar cell are also treated by the new selective process. Tin is directly deposited on Aluminum back contact showing adhesion higher than silver on silicon (i.e. > 1N/mm). © 2013 The Authors
AMPERE: An European project aimed to decrease the Levelized Cost of Energy with innovative heterojunction bifacial module solution ready for the market.
No full textAMPERE project aims to the setting-up of an innovative 100 MWp/y full-scale automated pilot line delivering a power module of 390 Wp based on an industrial heterojunction solution with a bifacial architecture (G/G 72-cells).}} \textbf{A rapid scale up to 240 MWp/y is planned and a pathway towards the GWp/y factory defined. The implementation of the heterojunction technologies into these industrial manufacturing lines will demonstrate that the production of PV products at a remarkable decrease of LCOE is possible. The project will target an LCOE reduction of at least 15% compared to mainstream PV mc-Si technology. © 2018 IEEE
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