Refined nano-textured surface coupled with SiNx layer on the improved photovoltaic properties of multi-crystalline silicon solar cells

• Optical reflectance of NP-Si and NIP-Si has been systematically investigated.
• The NIP-Si solar cells have better photovoltaic properties.
• It is due to reduced reflectance, improved spectral responses and diode parameters.
• An optimum design strategy has been suggested to gain better results.

Nano-porous silicon (NP-Si) and nano-inverted-pyramid silicon (NIP-Si) structures have been formed by Ag-catalyzed chemical etching without and with NaOH modification on solar-grade multi-crystalline silicon substrates, respectively. The influence of nano-structured morphology (NSM) and SiNx layer (SL) on effective reflectance (Reff) has been investigated through measurement and simulation. For typical NP-Si and NIP-Si samples, the NSM alone can suppress Reff of NP-Si sample to the lowest degree (5.87%), and the combination of NSM and SL is favorable to gain the lowest optical loss for NIP-Si sample (Reff = 7.31%). Compared with NP-Si solar cell, the fabricated NIP-Si solar cells have hugely improved photovoltaic properties, resulting from reduced reflectance in visible and near-infrared wavelength, enhanced short-wavelength spectral responses and good diode parameters. Finally, an optimum design strategy of NSM and SL has been suggested to gain potentially better properties for nano-structured solar cells.