Nanoporous black multi-crystalline silicon solar cells: realization of low reflectance and explanation of high recombination loss

Nanoporous black silicon (nb–Si) structures with/without saw damage removal (SDR) on solar-grade multi-crystalline silicon substrates have been formed by simple Ag-induced chemical etching. The  nb–Si shows a unique morphology of nano-scale holes on micron-scale patterns with low reflectance (<5%). The photovoltaic properties of nb–Si solar cells show that SDR process prior to Ag-induced chemical etching is an effective way to lower recombination and ohmic losses, resulting in significant efficiency enhancement of 26.0%. To further reduce the recombination loss for the nb–Si solar cells with ∼10% efficiency, a two-layer emitter model has been introduced to explain the reduced emitter diffusion length that significantly lower spectral response. This suggests that removing residual Ag nanoparticles completely might be the key approach to enhance the spectral response of nb–Si solar cells with very low surface reflectance, thus increasing the final conversion efficiency.