On the Enhanced Phosphorus Doping of Nanotextured Black Silicon

The integration of nanotextured black silicon (B-Si) into solar cells is often complicated by its enhanced phosphorus doping effect, which is typically attributed to increased surface area. In this article, we show that B-Si's surface-to-volume ratio, or specific surface area (SSA), which is directly related to surface reactivity, is a better indicator of reduced sheet resistance. We investigate six B-Si conditions with varying dimensions based on two morphology types prepared using metal-catalyzed chemical etching and reactive-ion etching. We demonstrate that for a POCl3 diffusion, B-Si sheet resistance decreases with increasing SSA, regardless of surface area. 2-D dopant contrast imaging of different textures with similar surface areas also indicates that the extent of doping is enhanced with increasing SSA. 3-D diffusion simulations of nanocones show that both the extent of radial doping within a texture feature and the metallurgical junction depth in the underlying substrate increase with increasing SSA. We suggest SSA should be considered more readily when studying B-Si and its integration into solar cells.

Automated summary

This article investigates the impact of specific surface area (SSA) on sheet resistance in the integration of nanotextured black silicon (B-Si) into solar cells. The study suggests that SSA is a better indicator for reducing sheet resistance. Doping level of B-Si increases with higher SSA, as indicated by 2-D dopant contrast imaging, and 3-D diffusion simulations show that radial doping and metallurgical junction depth also increase with higher SSA.