Inverted Pyramid Texturization of Monocrystalline Silicon Surface by Cu-Assisted Chemical Etching at Different Conditions

Texturization of silicon surface is a commonly applied procedure to reduce surface reflection of the incident sunlight in solar cells. In this study, inverted pyramid (IP) structures were successfully created on the silicon surface using a single-step Cu-assisted chemical etching method, where Cu acted as catalyst and HF as the etching agent. Texturization was carried out at different HF concentrations and etching durations, to see their corresponding effects on the morphology and light trapping ability of the silicon surface. For a fixed etching duration of 10 min, the best uniformity and optimal etching depth for IPs was obtained with an HF concentration of 4.5 M. This structure gave a surface reflectivity of 7.92%, which was significantly lower than that obtained from the upright pyramidal m-Si wafer prepared by alkaline chemical etching for comparison. The reflectivity was reduced to 5.97% through optimization of the etching duration as 15 min, and further reduced to 2.69% after passivation with SiO₂, SiN_x and AlO_x. This sample produced remarkable efficiency (22.24%) and short-circuit current (10.12 A) in a PERC solar cell which were significantly higher than the cell utilizing upright pyramid texture. Overall results show that the solar cell efficiency can be improved through the optimization of inverted pyramid textures on monocrystalline silicon.