Surface Texturing of Crystalline Silicon Solar Cell Using Silicon Nanowires

Abstract

Surface texturing with silicon nanowires on a pyramidal structure was explored by simple metal-assisted chemical etching to improve the electrical performance of a silicon solar cell. The length of nanowires was controlled by changing the etching time in a H2O2/HF solution after Ag ion adsorption. The weighted reflectance from 300 to 1200 nm was reduced to as low as 4.6% with a 200-nm-long nanowire formed by 30 s etching, while the pyramid surface had a 12.3% reflectance before antireflection (AR) coating deposition. However, the surface textured with 200-nm-long silicon nanowires had a similar reflectance, even after AR coating, and a decreased conversion efficiency in the completed solar cell. Since the silicon wafer with 200-nm-long nanowires had a deep and narrow structure, the AR layer could not be deposited uniformly, which resulted in a low passivation quality and an antireflection effect. This means that the surface structure, even with low reflectance, cannot be appropriate in the cell fabrication process because it is not capable of improving the solar cell performance characteristics. On the other hand, the 30-nm-long nanowire-textured silicon solar cell formed by 2 s etching had a decreased reflectance and improved electrical properties. As a result, the 30-nm-long silicon nanowire-textured solar cell exhibited improved performance characteristics, ΔJsc = 0.3 mA/cm2, ΔVoc = 2 mV, and Δη= 0.2%, compared with only a pyramidal textured surface. This suggests that a respectable quality in the passivation and antireflection layers, as well as reflectance reduction, in nanoscale-textured silicon solar cells is required for silicon solar cell performance.