Overcoming Throughput Limitations of Laser Systems in Solar Cell Manufacturing via On-The-Fly Processing using Polygon Scanners

In this paper, a high-throughput on-the-fly laser processing system for the manufacture of silicon solar cells is proposed. Industrial laser processing machines are systematically limited in a trade-off between throughput and focal spot size. Additionally, today's laser power and repetition rates cannot be fully utilized because of limited galvanometer scan speeds. This work aims to overcome this using a polygon scanner in an on-the-fly laser processing operation. Unlike conventional approaches, this setup does not use high-precision positioning systems, but reduces wafer transport to a simple conveyor belt to optimize system cost, space, integrability, and cycle rate. The concept is implemented in a demonstrator setup. Applying a laser contact opening process, a throughput of 10 000 wafers per hour is demonstrated. A potential throughput of 13400 wafers per hour is calculated, considering the utilization of more powerful lasers. Inaccuracies due to the unevenness of the surface as well as transport speed oscillations are analyzed and shown not to have an impact on the efficiency of the cells processed with this setup. The throughput is increased five times compared to the theoretical upper-throughput limitation for the same structure processed by a galvanometer-driven laser system.