Laser Processing of Thin Films for Photovoltaic Applications

This paper discusses the structuring of several thin film materials used for solar cells, e.g. SiN x , SiO 2 and Transparent Conductive Oxides (TCOs). The focus of the experiments is to obtain an optimal edge quality without damaging the substrate below the structured region. Two important laser parameters are wavelength and pulse duration which determine the absorption of the laser radiation in the processed material and the extent of heat influence on the surrounding material. Processing with several wavelengths (e.g. 532 nm and 1064 nm) and pulse durations especially in the pico-and nanosecond range is studied. The results obtained with the different laser parameters are compared by considering ablation threshold, debris, and damage due to heat conduction. The quality of laser processing is determined by optical and scanning electron microscopy. Results from the structuring of TCOs and organic layers are acquired with different laser types. Additionally, comparisons are made regarding the achievable structuring quality for mass production, relevant speeds around 1 m/s for thin films and 1-2 seconds processing time for wafer based cells.