Efficient light trapping in silicon solar cells by ultrafast-laser-induced self-assembled micro/nano structures

A novel ultrafast laser processing technique is used to create self‐assembled micro/nano structures on a silicon surface for efficient light trapping. Under appropriate experimental conditions, light reflection (including scattering) of the Si surface has been reduced to less than 3% for the entire solar spectrum and the material appears completely black to the naked eye. A post‐chemical cleaning is applied to remove laser‐redeposited material and induced defects. Optical, morphological, and structural characterizations have been carried out on as‐laser‐treated and post‐chemically cleaned surfaces. Finally, we report for the first time the total efficiency of over 14% and high external quantum efficiency (EQE) results on photovoltaic devices fabricated on the ultrafast‐laser‐induced micro/nano structured silicon wafer, which can be further improved upon process optimization. Copyright © 2011 John Wiley & Sons, Ltd. A novel ultrafast laser processing technique is used to create self‐assembled micro/nano structures on crystalline and multi‐crystalline silicon surfaces for efficient light trapping. Light reflection (including scattering) of the Si surface has been reduced to less than 3% for the entire solar spectrum and the material appears completely black to the naked eye. We report for the first time the total solar cell efficiency of over 14% fabricated on the ultrafast‐laser‐induced micro/nano structured crystalline Si wafer.