Micro- and nanoparticle generation during nanosecond laser ablation: correlation between mass and optical emissions

The particulate emission during nanosecond ablation of gold targets was investigated at various fluences (10-100 Jcm(-2)) and vacuum levels (0.05-750 Torr). Atomic emission spectra were acquired during the ablation process and post-mortem characterization of particle spatial distribution was performed using scanning electron microscopy. The discussion of the results in the context of existing theoretical models permitted the identification of four distinct mass removal mechanisms. While the presence, shape and intensity of atomic emission lines is a telltale of the nanoparticle formation process, the fluctuations of the emission signal over a number of laser shots was linked to the production of microscopic debris

Silicon solar cell production line and key performance indicators: A case of study at front size serigraphy stage

Photovoltaic industry has devices power improvement as a main target. This implies that technological advances are continuously implemented in production lines and their power improvements have to be monitored with the suitable key performance indicators. In this work, front size serigraphy design has been selected as process improvement and laminated unit power and cell to module ratio has been defined as the main key performance indicator. Real size silicon PV cells with three different front finger morphologies have been produced in industrial production lines by the use of two front size serigraphy designs. The modification of the finger dimensions (wide/height) from (183.0 μm/31.6 μm) to (184.0 μm/37.6 μm) and (140.0 μm/40.8 μm) leads to a redistribution of the majority produced cell power range from [4.10–4.15) W to [4.10–4.15) W and [4.20–4.25) W respectively. Concerning the cell production, it has successfully been monitored by the laminated unit power indicator along a month when shows an increment from 3.95 W to 4.20 W. Concerning module level, cell to module ratio per process cell range is selected as suitable indicator and monitoring during a year. In the specific case of [4.30–4.35) W cell range, cell to module ratio decrease from 7.7 % to 6.5 %The authors are thankful to Erasmus+ Programme, SafeEngine project, contract no 2020-1-RO01-KA203-080085, Spanish Ministerio de Ciencia e Innovación through project PID2020-117832RB-100, UMA 18-FEDERJA-041 for their support and to Isofoton and J. Alcaide and J. Rando from 4TENERGY S.COOP:AND, for their collaboration. Funding for open access charge: Universidad de Málaga / CBU

N coordination chemistry in diluted InGaAs nitride layers

GaAsN and InGaAsN semiconductor alloys with a small amount of nitrogen, so called dilute nitrides, constitute a novel compounds family with applications in telecom lasers and very efficient multijunction solar cells. The incorporation of N, which has a much larger electronegativity and smaller atomic size compared to As, induces a strong structural distortion in the InGaAs coordination chemistry, which will also affect the material electronic structure and band-gap. In particular, the nearest-neighbour bonding configuration of the N in InGaAsN has proven its influence on the band-gap. Our ARXPS results demonstrate that a higher growth temperature favour the formation of In-N bonds.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. - MINECO through TEC2011-28639-C02-02 and TEC2014-54260-C3-3-P - Wroclaw University of Technology statutory gran

Differences in n-type doping efficiency between Al- and Ga-ZnO films

A careful and wide comparison between Al and Ga as substitutional dopants in the ZnO wurtzite structure is presented. Both cations behave as n-type dopants and their inclusion improves the optical and electrical properties of the ZnO matrix, making it more transparent in the visible range and rising up its electrical conductivity. However, the same dopant/Zn ratio leads to a very different doping efficiency when comparing Al and Ga, being the Ga cation a more effective dopant of the ZnO film. The measured differences between Al- and Ga-doped films are explained with the hypothesis that different quantities of these dopant cations are able to enter substitutionally in the ZnO matrix. Ga cations seem to behave as perfect substitutional dopants, while Al cation might occupy either substitutional or interstitial sites. Moreover, the subsequent charge balance after doping appear to be related with the formation of different intrinsic defects that depends on the dopant cation. The knowledge of the doped-ZnO films microstructure is a crucial step to optimize the deposition of transparent conducting electrodes for solar cells, displays, and other photoelectronic devices.Ministerio de Ciencia e Innovación TEC2007-60996, MAT2008-06858-C02-02, MAT2008- 06330, TEC2010-16700FUNCOAT CSD2008-00023- CONSOLIDER INGENIOSonderforschungsbereich SFB 76

Electrochemical impedance spectroscopy analysis of chalcopyrite CuFeS 2 electrodes

Abstract A chalcopyrite CuFeS 2 electrode obtained from the ''El Teniente'' mine has been studied by Electrochemical Impedance Spectroscopy (EIS) in an alkaline solution for different oxidation potentials. The experimental results can be interpreted from a Randles equivalent circuit, V dc <0.4 V vs. saturated calomel electrode (SCE), and a surface layer model for V dc >0.4 V vs. SCE. From these results, the variation with the d.c. applied potentials of charge transfer electrical resistance of the redox reaction, the double layer capacitance and other characteristic parameters are considered

ARXPS analysis of a GaAs/GaInP heterointerface with application in III-V multijunction solar cells

In this contribution, angle-resolved X-ray photoelectron spectroscopy is used to explore the extension and nature of a GaAs/GaInP heterointerface. This bilayer structure constitutes a very common interface in a multilayered III-V solar cell. Our results show a wide indium penetration into the GaAs layer, while phosphorous diffusion is much less important. The physico-chemical nature of such interface and its depth could deleteriously impact the solar cell performance. Our results probe the formation of spurious phases which may profoundly affect the interface behavior

LSCF-CGO nanocomposite cathodes deposited in a single step by spraypyrolysis.

La0.6Sr0.4Co0.2Fe0.8O3-δ-Ce0.9Gd0.1O1.95 (LSCF-CGO) nanostructured cathodes with different LSCF-content are prepared in a single step by spray-pyrolysis deposition, simplifying notably the fabrication process compared to the traditional methods. The phase formation, structure, microstructure and electrochemical properties of the cathodes are investigated as a function of the CGO-content and the temperature by using X-ray diffraction, electron microscopy and impedance spectroscopy. The addition of CGO to LSCF limits the grain growth, giving rise to fine particles of approximately 30 nm of diameter after sintering at 800 °C. A small particle size of 50 nm is retained even after sintering at 1000 °C. However, the polarization resistance, determined by impedance spectroscopy, is not significantly improved with the CGO-addition. The performance of these nanocomposite electrodes, investigated in NiOeCGO anode-supported cells, shows an improved power density of 0.9 Wcm−2 at 650 °C, compared to 0.56 Wcm−2 for a conventional screen-printed cathode

A novel multilaminated composite cathode for solid oxide fuel cells.

A novel electrode architecture consisting in alternating layers of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) and Ce0.9Gd0.1O1.95 (CGO) is prepared for the first time by spray-pyrolysis deposition and investigated as cathode material for Solid Oxide Fuel Cells (SOFCs). Cathodes with different number of LSCF/CGO bilayers (N=0, 3 and 5) are prepared and characterized. The multilaminated cathodes are highly porous with connected vertical channels and display an unusual undulated morphology, which increases the contact area between CGO and LSCF materials. The oxygen reduction activity has been investigated by impedance spectroscopy, obtaining improved values of polarization resistance as the number of bilayers increases due to extended three-phaseboundary (TPB) length for the oxygen reduction reactions

Open-atmosphere structural depth profiling of multilayer samples of photovoltaic interest using laser-induced plasma spectrometry

The present work aims to assess Laser-Induced Plasma Spectrometry (LIPS) as a tool for the characterization of photovoltaic materials. Despite being a well-established technique with applications to many scientific and industrial fields, so far LIPS is little known to the photovoltaic scientific community. The technique allows the rapid characterization of layered samples without sample preparation, in open atmosphere and in real time. In this paper, we assess LIPS ability for the determination of elements that are difficult to analyze by other broadly used techniques, or for producing analytical information from very low-concentration elements. The results of the LIPS characterization of two different samples are presented: 1) a 90 nm, Al-doped ZnO layer deposited on a Si substrate by RF sputtering and 2) a Te-doped GaInP layer grown on GaAs by Metalorganic Vapor Phase Epitaxy. For both cases, the depth profile of the constituent and dopant elements is reported along with details of the experimental setup and the optimization of key parameters. It is remarkable that the longest time of analysis was ∼10 s, what, in conjunction with the other characteristics mentioned, makes of LIPS an appealing technique for rapid screening or quality control whether at the lab or at the production line