Thermal stresses and cracking behavior during laser crystallization of silicon on glass for thin film solar cells

During the preparation of silicon thin film solar cells on glass substrates by diode laser induced liquid phase crystallization (LPC), cracking is an issue. This is due to thermal stresses caused by high temperature gradients within the sample. In this paper, the relation between thermal stress and the temperature distribution within the sample during LPC is discussed. Experiments for two sets of laser irradiation parameters were done leading to crack free or cracked crystallization of the film. Additionally, the evolution of temperature during LPC was modeled numerically. Based on the simulation, the thermal stresses introduced were calculated. The complex viscoelastic problem was simplified to an elastic multilayer model, which can be solved analytically. The theoretical results can explain the experimental behavior.

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