Laser Assisted Etching (LAE) technique with short laser wavelength was used to provide a gradient-porosity porous silicon (GPSi) layer. Morphological aspects, reflectivity and photoelectric properties of (GPSi) layer were studied based on a bare solar cell substrate (p-n). The results show that the (GPSi) layer has a lower reflectivity of about (1.3%) comparing with bulk silicon (reference sample 50%) and single layer PSi of about (10.5%) at wavelength regime (400 nm). The surface morphology and x-section images present the formation of (GPSi) with layer thickness of about (400 nm) less than the junction depth. The photoelectrical properties of (GPSi) layer shows an increase of short circuit current density of (2.8 mA/cm2 ) compared with the ordinary solar cell of (2.15 mA/cm2 ) while for single layer PSi is about (2.05 mA/cm2 ).
Keywords: porous silicon, gradient-porosity porous silicon, reflectivity, solar cell.