Depth selective laser scribing for thin-film silicon solar cells on flexible substrates

Roll-to-roll production facilitates flexible PV modules and a significant decrease of production cost for thin-film silicon solar cells. However, no standard processes for monolithic series interconnection on opaque foil substrates are readily available. In this contribution, we present different approaches to achieve depth selective laser scribing of thin-film silicon solar cells on electrically insulated steel foil. Besides paving the way to series interconnection on opaque flexible substrates, this concept also allows to significantly reduce the number of process steps during module manufacturing. The required depth selective scribes can be obtained with all three employed Diode Pumped Solid State-lasers (wavelengths of 355 nm, 532 nm, and 1064 nm). Actually, several laser parameter combinations (wavelength, pulse energy, spot overlap, single/multi-pass) have been found to make scribes that meet the requirements of the device architecture. Currently, the electrical validation of the observed scribes is in progress. In a next step, fully series interconnected modules will be manufactured following the presented device and processing concepts.