Concept and realization of a high-rate laser drilling process reaching for ten thousand holes per second and beyond

Abstract

A major breakthrough on the way to cheap sustainable solar electricity generation is the back contact solar cell. By moving both terminals to the back of the solar cell shading losses can be reduced or eliminated, which leads to higher cell efficiencies. One concept to achieve this, the emitter wrap-through (EWT) solar cell, requires holes drilled through the silicon wafer with a density of up to one hole per mm², i.e. up to 24,000 holes on a 6 wafer.The present situation of the solar cell industry demands high processing speeds and a high production throughput. For an industrial EWT solar cell production line, a throughput of 10,000 vias/sec and more is essential and this depends heavily on the laser performance. In this work, this is tackled by developing optical concepts such as beam splitting and the combination of ultra-fast scanning and simultaneous movement of a linear axis. Also, the selection of the proper laser source and processing parameters has proven to be crucial to successfully achieve the desired drilling rates. Of course, other applications, such as laser drilling of filters can benefit from these developments.A major breakthrough on the way to cheap sustainable solar electricity generation is the back contact solar cell. By moving both terminals to the back of the solar cell shading losses can be reduced or eliminated, which leads to higher cell efficiencies. One concept to achieve this, the emitter wrap-through (EWT) solar cell, requires holes drilled through the silicon wafer with a density of up to one hole per mm², i.e. up to 24,000 holes on a 6 wafer.The present situation of the solar cell industry demands high processing speeds and a high production throughput. For an industrial EWT solar cell production line, a throughput of 10,000 vias/sec and more is essential and this depends heavily on the laser performance. In this work, this is tackled by developing optical concepts such as beam splitting and the combination of ultra-fast scanning and simultaneous movement of a linear axis. Also, the selection of the proper laser source and processing parameters has proven to be crucial to successfully achieve th...