During the last years, the photovoltaic solar cell industry has experienced enormous growth. However, for solar cells to be competitive on the longer term, both an increase in their efficiency as well as a reduction in their cost is necessary. This paper discusses some opportunities of laser technology to realize these improvements.
An effective method to reduce costs of silicon solar cells is reducing the wafer thickness, because silicon causes a large part of the costs. Consequently, for applying the emitter contact fingers on the solar cell, contact free laser processing has a large advantage in contrast to commonly used print screen techniques. This is because of less scrap due to broken wafers. Additional, many novel high efficiency solar cell concepts are only feasible with laser technology, e.g. due to the requirement for drilling a few thousand holes per second in brittle materials.
In this paper, experimental investigations are discussed for producing grooves and holes in silicon wafers according to a recently developed solar cell concept. The amount of heat affected silicon in the surrounding of the processing is minimized. Any unavoidable heat affected material and debris is subsequently removed with a chemical etching process. Laser processing is studied with a variety of pulsed laser sources like excimer lasers, Nd:YAG lasers and frequency converted solid state lasers with a variety of wavelengths. Furthermore, different types of lasers are compared regarding their processing quality and processing time.