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Thermal Stress Minimization in Silicon Ribbon Growth Processes by Thermal Gradients Modulation with 808 nm Laser Scanning
D.M. Pera, M.C. Brito, A.M. Vallêra, J.M. Serra, J.M. Alves
Laser Processing, Silicon (Si), Ribbons, Crystallization
Silicon Cells
Subtopic: Feedstock, Crystallisation, Wafering, Defect Engineering
Event: 35th European Photovoltaic Solar Energy Conference and Exhibition
Session: 2AV.1.18
498 - 500
ISBN: 3-936338-50-7
Paper DOI: 10.4229/35thEUPVSEC20182018-2AV.1.18
0,00 EUR
Document(s): paper, poster


The temperature profile near the solid-liquid interface in the crystal growth direction is an important parameter since it will affect crystal defects structure. The bi-dimensional geometry of silicon ribbons reduces, by principle, the complexity of cooling gradients control when compared with traditional industrial directional solidification. In this work, we present a method to modulate and actively control the temperature distribution during growth of silicon ribbons. The method was explored in a silicon ribbon growth experimental set-up based on electric molten zone, EZ-Ribbon. Electric molten zone (EMZ) crystallization is a method that relies on silicon’s electric conductivity increase with temperature. A positive feedback pattern leads to virtually all current collapsing into a thin molten capillary. The high power 808nm diode laser scanner used to stimulate locally the EMZ formation was also used to control the contiguous temperature distribution in the crystallization direction. The EZ-Ribbon technique configures a float zone method, featuring attractive kerfless, contamination-free and low energy budget crystallization mechanism. In particular, high crystalline quality may be, in the near future, its main issue regarding the present laser assisted thermal gradient modulation procedure.