Texturing low reflecting surface of random double inverted pyramids using N-fluoropyridinium salt

Here we propose a texturing method for crystal Silicon solar cells, which enables a low reflecting surface of random double inverted pyramids easily. The surfaces of the reported crystal Silicon solar cells that have world-record efficiency were inverted pyramids, whereas the widely-used conventional texturing surface is a random pyramid surface by alkaline solution. Our method can realize a random double inverted pyramid surface of nanometer-sized inverted pyramids on micrometer-sized inverted pyramids without photo-lithography. This random double inverted pyramid surface is obtained by a kind of fluorinating agent of N-fluoropyridinium salt, under optical illuminating and heating condition. Using reflectance measurement with integrating sphere, we realized a black surface of 6.3% reflectance, whereas the as-slice surface is 23% and random pyramid surface is 11.9%.