A novel laser scribing method combined with the thermal stress cleaving for the crystalline silicon solar cell separation in mass production

Abstract

Nowadays as the wafer sizes of the crystalline silicon solar cells get larger and larger, separating the cells becomes an essential step. However, in mass production, there is still lack of a low scribing loss and broad compatible cell separation method. In this work, a systematic investigation was conducted on the crystalline silicon solar cell separation processes, including the laser scribing and the cleaving process. Firstly, by combining a 1/4 beam splitter with the laser head, we developed a new laser scribing process, which can achieve a smaller groove width-to-depth ratio (24%) with narrower heat affected area (total width of 30 μm) compared to traditional laser optical systems. Then, we explored the minimum required scribing depths for separating four typical crystalline silicon cells by applying the thermal stress cleaving process. The Czochralski-grown substrates need only point scribing at the beginning and the end of the separating path, but if there is a metal electrode in the separation path, the scribing depth has to be about 20% of the cell thickness. At last, we analyzed the electrical and mechanical strength losses caused by different separation processes. The 20% scribing depth may cause about 30%rel mechanical strength loss. It is proved that combining this new scribing method with the thermal stress cleaving is an economical separation solution with less laser scribing loss and better compatibility for different cells. Our results would shed some light on future separating and module design efforts of solar cells.