Infrared measurement of undercooling during silicon solidification on bare and Si3N4 coated quartz substrates

• A method provides reliable undercooling values and visualizes the process.
• The high accuracy of undercooling values is got with less the background radiation.
• The measurement is less than 10 min.
• The observed Si morphologies and the measured undercooling values are consistent.

Undercooling is one of the most significant parameters in the solidification of silicon since it controls the grain structure formation, which determines the final performance of solar cell. Here a new and simple experimental facility is proposed to provide reliable undercooling values and visualize the melting-solidification process when silicon solidifies on a bare and a Si3N4 coated quartz (SiO2) substrate. A lamp heating system was used for the melting, the undercooling temperature was measured with the aid of an infrared single-color pyrometer while the morphologies of the growing silicon on the SiO2 and Si3N4-coated SiO2 substrates are also investigated through a digital microscope. The high precision and accuracy of the given undercooling values when using the present setup comes from the principle of minimizing the background radiation that can significantly influence the pyrometer measurements.