Black silicon is very promising for the third generation Solar Cells, because of its fascinating light absorption of above
98% in visible spectrum and more than 90% in 800-2500 nm, and its surface micro-nano structures enlarge light trapping
intermediate impurities levels caused by supersaturated doping expand absorptive limitation of crystalline Si. In recent
years femtosecond laser pulses were widely used in the process of improving the absorptance by irradiating silicon
surfaces with in the presence of different gases. Nevertheless, picosecond laser used to fabricate large-area black silicon is seldom reported. A diode-pumped picosecond Nd:YAG regenerative amplifier laser system designed for microstructuring the crystalline silicon was reported in this paper. At the repetition of 1 kHz, the system generated 1 W average-power, 26-ps-long pulses with a pulse energy of 1 mJ at 1064 nm, which corresponds the peak power of 38.5 MW. A 0.5 W second-harmonic 532 nm laser is achieved with a 20 mm long noncritically phase-matched lithium triborate (LBO) crystal from the 1W 1064 nm laser. igh optical absorption black Si irradiated with 1064 nm and 532 nm picosecond pulses in SF6 at different laser fluence. And the relationship between the surface morphology and the wavelength or the laser fluence was researched.
Different sidewall characters of the silicon microholes drilled with fiber laser pulses at 1065.2 nm were examined by a
scanning electron microscope. It shows two different recast phases on the hole-wall: mild melt phase with smooth
interface and vaporization phase with rough interface. These two recast phases show different etch rate when alkaline
texturing, which sometimes leave some undesirable damages on the sidewall. After alkaline texturing, the taper holes
transform into octagonal holes. And the eight sidewalls of the octagonal-hole alternating appear two different micro-nano structures, one is pyramid structure, the other is lamellar structure.