Towards high-efficiency Al-BSF c-Si solar cell with both superior omnidirectional and electrical performance by modulating the tilt angle of quasi-periodic inverted pyramid arrays

Seeking efficient light trapping structures with both superior omnidirectional and electrical performance is always on the way for increasing electrical energy output of c-Si solar cell over a wide range of light incident angle (theta). Here, tile angle (delta) of quasi-periodic structure arrays is systematically modulated from 35.9 degrees to 72.8 degrees on diamond-wire-sawn (DWS) c-Si by a simple and cost-effective Cu and Ni co-assisted chemical etching way followed by a post treatment. Interestingly, compared with the conventional micro pyramid (MP), the optimized inverted pyramid (IP) like arrays with a delta of 64 degrees possess both lower light reflectance and carrier recombination, leading to a corresponding solar cell with a higher efficiency (similar to 19.67%) than that of MP based counterpart (similar to 19.31%). Moreover, during the increase of theta, the external quantum efficiency (EQE) of 64 degrees IP based cell drops much more slowly than that of MP based one by properly adjusting the relative position of the structure arrays and incident light, indicating its omnidirectional property. Simultaneously, a maximum relative enhancement of electrical output power approaching similar to 5.8% in the theta range of -90 degrees-90 degrees is achieved on 64 degrees IP based cell compared to the MP based one, the mechanism behind which is further explained by optical simulation. The above finds pave a new way to increase the electrical energy output in a simple and cost-effective way.