Shape-Controlled Silicon Microwire Arrays from Au–Ag-Catalyzed Metal-Assisted Chemical Etching for Radial Junction Solar Cells

Metal-assisted chemical etching (MaCE) has been extensively studied as a cost-effective way to produce silicon nano/micro structure arrays. However, it is hard to keep the resultant morphologies of the nano/micro structures exactly consistent with the original designs because the MaCE process is affected by multiple factors, such as catalyst type, etching solution, temperature, and the interaction with one another. Here, we first proposed an etching model to address the different MaCE behaviors of using Ag, Au, and Ag/Au as catalysts. The model was then independently proven by systematic experiments on the Ag/Au catalyst, with the Au film playing mainly as the frame and the lower Ag film boosting the catalytic activity by increased tiny cavities. With the Ag/Au catalyst, silicon nano/micro arrays with smooth and controllable morphologies from the bottom to the top surface can be successfully formed. Finally, fine-tuned silicon microwire arrays were applied to produce radial junction solar cells, showing a 1.8% increase in absolute efficiency in comparison with the reference cell made by a single metal catalyst. Our findings show that the modified MaCE with Ag/Au catalyst can be an effective way to acquire shape-controlled solar cells with enhanced efficiency.