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Gennevilliers, France

Johnson E.V.,Ecole Polytechnique - Palaiseau | Prodhomme P.,Total S.A. | Boniface C.,EXCICO France SAS | Huet K.,EXCICO France SAS | And 2 more authors.
Solar Energy Materials and Solar Cells

We demonstrate the effect of excimer (XeCl=308 nm) laser annealing on thin films of ZnO:Al deposited by RF sputtering at room temperature. The as-deposited films have good sheet resistance (<11 Ω/□) but poor transparency, and a subsequent chemical etching step using dilute HCl to texture the film surface results in a level of haze ineffective for light-trapping in thin film photovoltaic cells. Excimer laser annealing at the optimized fluence (single pulses of 0.50.7 J/cm2) improves the film transparency, particularly through a blue-shift in the band-gap, without significantly impacting the conductivity. More importantly, chemical etching of these laser annealed films results in textured films with controllable spectral distributions of haze. We demonstrate the enhanced optical properties (transmission and haze) after laser annealing and etching the ZnO:Al films through the fabrication of hydrogenated microcrystalline silicon pin solar cells, and show a significant improvement in the photocurrent density (up to 2.2 mA/cm2) for the optimally annealed substrates - particularly at wavelengths greater than 600 nm (up to 1.7 mA/cm2) where light-trapping is important. © 2011 Elsevier B.V. All rights reserved. Source

Tous L.,IMEC | Tous L.,Catholic University of Leuven | Granata S.N.,IMEC | Granata S.N.,Catholic University of Leuven | And 17 more authors.
Energy Procedia

Ni/Cu plated front contacts are applied to large-area hybrid silicon heterojunction (SHJ) solar cells consisting of a diffused front surface field and intrinsic and boron doped a-Si:H(i/p+) layers forming the rear SHJ emitter. Nickel silicide front contacts are formed by excimer laser annealing (ELA) which unlike rapid thermal annealing (RTA) is shown to be compatible with a rear SHJ emitter. A top efficiency of 20.1% (externally confirmed at FhG-ISE CalLab), with jsc=39.0 mA/cm2, Voc=675.1mV, and FF=76.5% is obtained on 15.6x15.6 cm2 n-type Cz-Si in a first trial and this without compromising solder tab adhesion results at the front side. Limitations arising from series resistance at the rear side and from recombination at the front side are discussed. © 2014 Published by Elsevier Ltd. Source

Charpentier C.,Total S.A. | Charpentier C.,Ecole Polytechnique - Palaiseau | Boukhicha R.,Ecole Polytechnique - Palaiseau | Prod'Homme P.,Total S.A. | And 4 more authors.
Solar Energy Materials and Solar Cells

The use of a combined excimer (XeCl=308 nm) laser annealing (ELA) and chemical etching process (dubbed the "LaText" process) to generate textured ZnO:Al thin films suitable for thin-film silicon photovoltaic applications has been previously shown, but the evolution of the material during the laser annealing and texturing steps has not been thoroughly examined. In this work, we examine in detail the evolution of the properties of room-temperature sputtered ZnO:Al thin films during such a process. We reveal (i) the bulk structural changes induced during laser annealing through X-ray diffraction measurements (XRD) and Raman spectroscopy, (ii) the dramatic changes in surface morphology and macroscopic electronic properties before and after each step of the LaText process, through Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Hall effect measurements, and (iii) the exceptional light scattering properties of these films in both air and in a cell configuration, as measured by optical transmission and reflection measurements. In all, we show that the electronic transport properties in the final state are acceptable for thin film PV applications, and the optical properties are exceptional and demonstrate great potential for light-trapping performance for both a-Si:H and μc-Si:H solar cells. © 2014 Elsevier B.V. Source

Johnson E.V.,Ecole Polytechnique - Palaiseau | Charpentier C.,Ecole Polytechnique - Palaiseau | Charpentier C.,Total S.A. | Emeraud T.,EXCICO Group NV | And 5 more authors.
Materials Research Society Symposium Proceedings

We present a novel ZnO:Al fabrication process consisting of room-temperature vacuum sputtering followed by an excimer laser annealing (ELA). The ELA treatment improves the optical transmission of the films, and the film resistivities (<1 mΩ·cm) remain stable or improve with increasing laser fluence up to 0.6 J/cm 2, as the carrier density increases but the carrier mobility is degraded. This process is followed by a standard dilute HCl chemical texturing step, and produces substrates with suitable texture, conductivity, and transparency properties for thin-film photovoltaic applications. Substrates resulting from this process display elevated haze levels (80% at 600 nm and 50% at 800 nm) after the wet-chemical etching step. Such substrates have been used to make single junction hydrogenated nanocrystalline silicon solar cells, and an increase in the short-circuit current of up to 2.2 mA/cm 2 is observed compared to a substrate deposited by a standard room-temperature sputtering + wet-etch process. This gain is primarily due to increased photo-response in the red due to improved light-scattering, as at wavelengths greater than 600 nm, a gain in photocurrent of up to 1.7 mA/cm 2 is observed. © 2011 Materials Research Society. Source

Tous L.,Catholic University of Leuven | Tous L.,IMEC | Lerat J.-F.,EXCICO Group NV | Emeraud T.,EXCICO Group NV | And 10 more authors.
Energy Procedia

In this work, we report on a self-aligned nickel silicide formation technique based on excimer laser annealing (ELA). We evaluate this process for the front contact formation of industrial PERC type solar cells on random pyramid textured Si surfaces where damage to surface texture, emitter passivation, or to the shallow junction should be avoided or minimized. PERC type solar cells obtained by POCl3 diffusion were processed on large area (12.5×12.5 cm2) CZ-Si. Self-aligned litho-free Ni/Cu contacts defined by ps-laser ablation of the SiO2/SiNx anti-reflective coating (ARC) and subsequent ELA of the Ni layer were compared to conventional Ag screen printed contacts. The novel ELA process results in an absolute gain in Jsc of 0.8 mA/cm2 as well as a drop of 0.3 Ω.cm2 in series resistance (Rs) compared to SP Ag contacts due to reduced shading and resistance losses. This leads to 0.5% absolute increase in efficiency from 19.3% to 19.7% since other characteristics (Voc, pFF) could be maintained to the same level. In this work, the best performing cell with the ELA process reached an outstanding 20.0% energy conversion efficiency with Jsc=39.3 mA/cm2, Voc=649.8mV, and FF=78.3%. Source

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