Surface and optical characterization of the porous silicon textured surface for application in photovoltaics

In the present studies, the structural and optical properties of the electrochemically etched porous silicon layers (PS) are presented. The formation conditions were varied and, then to correlate the resultant surface morphology with the etching process. The low-porosity PS layers thus formed on the silicon substrate have a refractive index value (n_ps=1.9), which is an intermediate value between bulk silicon substrate (n_si=3.4) and air (n_air=1.0). The results of diffused reflectance, surface AFM, and FTIR show that resultant surface morphology of the PS layers consist of irregular and randomly distributed nanocrystalline Si structures. The reduction in reflection of the low porosity porous silicon layers is due to light scattering and light trapping of the incoming light by total randomization of the incoming light within the PS structure. Due to the reduced refractive index than the crystalline Si, the basic application of PS layers in PV technological point of view is an effective antireflection coating (ARC) for Si solar cells. The main advantage of the electrochemical etching to produce porous silicon layer on the heavily doped n⁺ emitter region of the PV cells is the simultaneous surface texture and significant reduction of the front surface reflection losses and sole surface passivation effects.