Two-Dimensional Numerical Analysis of Phosphorus Diffused Emitters on Black Silicon Surfaces

In this work, we present an analysis on electrical performance of phosphorus diffused emitters on black silicon surfaces through two-dimensional simulations. In particular, we focus on the extraction and analysis of the emitter saturation current density $(\boldsymbol{J}_{0\mathbf{e}})$, the sheet resistance $(\boldsymbol{R}_{\mathbf{sh}})$, spatial collection efficiency profile and relatedly $\boldsymbol{J}_{\mathbf{sc}}$ of a solar cell. Using process simulations, we form emitters on periodic triangular structures with various aspect ratios $(\boldsymbol{R})$ and emitter profiles. We show that for high aspect ratio and highly-doped structures, the trend of increasing $\boldsymbol{J}_{0\mathbf{e}}$ with junction depth, observed for planar structures, is reversed. While $\boldsymbol{R}_{\mathbf{sh}}$ increase with aspect ratio for shallow emitters, it is weakly dependent on aspect ratio for deep emitters, irrespective of the peak dopant concentration. For highly-doped emitters, the losses in $\boldsymbol{J}_{\mathbf{sc}}$ can be excessive if the junction depth is larger than the texture size. These losses are negligible for lightly-doped emitters regardless of aspect ratio and junction depth. The trends presented in this study for high aspect ratio emitters in comparison with one-dimensional emitters are expected to provide guidance in the identification of non-idealities that are observed in emitters formed on black silicon surfaces, such as additional surface and bulk defects.