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 POCl 3 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. Index Terms-Black silicon, phosphorus doping, silicon nanotexture, surface area, surface-to-volume ratio.
I. INTRODUCTIONN ANOTEXTURED silicon often falls under the collective label of black silicon (B-Si) which typically describes surfaces with low reflectance across a wide wavelength range (ultraviolet to near-infrared) and which appear black to the eye. B-Si can be prepared using a myriad of techniques and covers a wide range of surface morphologies and feature dimensions (from nano to micron-scale), including nanoporous layers [1],