||In this thesis, we would systematically investigate the importance of texturing surface. And we propose high efficiency HIT solar cell with pillar structure. Conventional HIT solar cell is a heterojunction structure which has a good open-circuit voltage. However, the reflectivity and shadowing effect limit the short-circuit current density. Most researchers understood the importance of reflectivity but they didn’t make a systematic investigation, for instance, the impacts from size and angle of pyramid. In order to make a systematic research, we use Silvaco TCAD to find best texturing surface structure. First, we optimized the size and angle of pyramid. The curvature of different pyramid is also discussed. The texturing surface is simulated according to (X / 15)n + (Y / 20)n = 1 which is named super-elliptic equation. The index n = 1 is a pyramid structure, n = 1.8 is a concave shape structure, and n = 0.2 is convex shape structure. From the simulation results, the convex shape of the structure has better anti-reflectivity. Pillar structure solar cells have better light trapping ability and anti-reflectivity than the conventional HIT solar cell. Under the ideal condition, the pillar can be deposited to 1.2 μm of gap, 1 μm of width, and 6 μm of height. Compares to the conventional HIT solar cell, our structure can improve the conversion efficiency from 24.70 % to 25.73 %.|
In fabrication, we use the metal-assisted etching to form the high depth and width ratio of pillars. The measurement of surface reflectivity shows that the pillar can decrease the reflectivity by 39 %. Pillar HIT solar cells have the best device of performance, which have the open-circuit voltage is 0.36 V, the short-circuit current density is 3.75 mA/cm2, the fill factor is 66.92 % and the conversion efficiency is 0.91 %.