A Numerical Model to Predict Contact Resistance During Contact Solidification in a Ribbon Growth on Substrate Process

The role of photovoltaics in the energy industry has become well known over the course of the past decade. One new method of manufacturing silicon solar cells is using the ribbon growth on substrate process (RGS). The contact resistance between the silicon and the substrate plays a critical role in the efficiency of the silicon wafer. A model for prediction the contact resistance at the solid-liquid interface for RGS process is created based on a discrete surface model and heat transfer model. The effect of radiation on the contact resistance is quantified for various surface and material properties and operational conditions. The model result without radiation is found to be consistent those obtained through analytical experimental study. Radiation is found to increase the heat transfer for substrates of rough surface and low thermal conductivity. Other parameters such as surface emissivity, melt temperature, and substrate temperature are also studied. It is found that these parameters have a moderate effect on the heat transfer coefficient. On the other hand, substrate surface roughness and thermal conductivity are prominent factors in heat transfer at the interface. A full model of RGS process is used to characterize the effect of contact resistance on the heat removed from the interface by the substrate. For typical surface and material properties, contact resistance is able to cause a substantial temperature drop at the solid-liquid interface. The effect of contact resistance on heat transfer at the interface for substrates of different materials and different pulling rates is also studied