High speed laser structuring of crystalline silicon solar cells

Fast laser processing is commonly done using a Gaussian laser beam in combination with a scanner. Single laser pulses only affect a limited area beneath the Gaussian intensity bell and result in circular impact regions. Adjacent impact regions have to overlap when continuous processing larger areas. Thus, the processing speed is greatly enhanced by replacing the Gaussian profile with a flat-top intensity profile and by replacing the radial symmetric cross section with a rectangular cross section. However, processing with a rectangular flat-top laser beam through a scanner has, to the best of our knowledge, not yet been demonstrated. We report on the successful design and experimental tests of a new laser system that images a rectangular flat-top profile through a scanner. Our so-called Simultaneous Scanning and Laser Beam Imaging - system (SIMSALABIM) machines a finger pattern that covers 50% of a (125 × 125) mm² crystalline Si solar cell in 14 s. Two parallel systems with increased output power should process the same area in just 2.5 s.