Title:	Modelling of Laser Ablation Processes for Applications in Thin Film Photovoltaic Technology
Author(s):	M. Colina Brito, C. Molpeceres, M. Morales, F. Allens-Perkins, G. Guadaño, J.L. Ocaña
Keywords:	Laser Ablation, Two Temperature Model, Thin Film Photovoltaic Technology
Topic:	Thin Films
Subtopic:	Amorphous and Microcrystalline Silicon
Event:	23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain
Session:	3AV.2.3
Pages:	2360 - 2366
ISBN:	3-936338-24-8
Paper DOI:	10.4229/23rdEUPVSEC2008-3AV.2.3
Price:	0,00 EUR
Document(s):	paper

Abstract/Summary:

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The fabrication of thin-film photovoltaic modules involves the use of laser ablation processes to carry out both the division of the module into individual cells and the serial connexion between them. Despite its wide industrial application, there is still room for improvement regarding the laser parameters that lead to optimal devices. Numerical simulation of the ablation process constitutes a powerful tool, not only to understand the physical process itself, but also for the prediction of possible changes that could negatively affect the treated material. The two-temperature model for thermal diffusion was numerically solved in this paper. Laser pulses of 1064 nm, 532 nm or 248 nm with duration of 35 ns, 26 ns or 10 ns were considered as the thermal source leading to the material ablation. The materials analyzed in the simulation were aluminium (Al) and silver (Ag), which are commonly used as metallic electrodes in thin-film photovoltaic modules. Moreover, thermal diffusion was also simulated for crystalline silicon (c-Si) as a first approximation to the study of amorphous silicon (a-Si) ablation, this material being used in silicon thin-film photovoltaic technology as the photosensitive one. For each material, the ablation depth dependence on laser pulse parameters (wavelength, pulse duration and fluence) was determined by means of an ablation criterion. Thus, after the laser pulse, the maximum depth for which the total energy stored in the material is equal to the vaporization enthalpy was considered as the ablation depth. Finally, the experimental validation of the simulation results was carried out and the ability of the model to closely fit experimental results was confirmed.