Effect of firing process on electrical properties and efficiency of n-TOPCon solar cells

Abstract

In the large-scale production of solar cells, metallization is a very important process, which directly affects the opening-circuit voltage, short-cut current, shunt resistance, and fill factor, thus affecting the efficiency of the solar cell. In this paper, the n-TOPCon process is matched by changing the firing temperature and belt speed of each zone to change the peak temperature and the width of the firing curve. After low-temperature slow firing (A1), the front contact resistance of the solar cell is the largest, and the Uoc and the Eff are the highest. However, after the electric injection, the Uoc and the FF increase are small, and the Eff is low, with an average value of 24.23 % and an increase of 0.04 %. After higher temperature and faster firing (AB2), the front-specific contact resistance of the solar cell is the smallest. Affected by the specific contact resistance, the solar cell has the highest FF, the lowest Uoc, and the lowest Eff. However, the electrical injection significantly increases the Uoc. The Eff after electric injection is the highest, with an average of 24.42 %, an increase of 0.36 %. The H ions in SiNx have different effects of passivation on the wafer under different firing conditions, but the difference is narrowed by the electrical carrier injection of H ions on the surface into the wafer. Therefore, solar cells with excellent electrical performance can be obtained by firing at appropriate peak temperature and firing width, obtaining low contact resistance first, and then increasing the Uoc and Jsc by electric injection.