Effect of Silicon Porosity on Solar Cell Efficiency

Porous silicon (PS) layers were fabricated on n-type crystalline silicon (c-Si) wafers of (100) and (111) orientations using photoelectrochemical etching (PECE) process at etching time of 20 min, current density of 60 mA/cm(2), and fixed electrolyte solution HF:C2H5OH (1:4). Moreover, PS layers fabricated on p-type c-Si wafers of (100) and (111) orientations using electrochemical etching (ECE) process were prepared under similar parameters. Nanopores with an average diameter of 5.7 nm were formed in the n-PS (100) layer. These nanopores increased the porosity of the material to 91% compared with those of the samples with different orientation and Si type. A greater blue shift luminescence was observed in the n-PS (100) layer compared with those of the other samples. The lowest effective reflectance was obtained with the n-PS (100) layer that exhibited excellent light-trapping at wavelengths ranging from 400 to 1000 nm. Solar cells were fabricated based on the PS anti-reflection coating (ARC) layers. The current-voltage characteristics of the solar cells were examined under 100 mW/cm(2) illumination. A highly efficient (15.5%) solar cell was obtained with n-PS (100) ARC layer compared with those solar cells with other layer types. In the present paper, the effect of the porosity of the PS ARC layers on the solar cell efficiency based on the n- and p-type regions with (100) and (111) orientations was investigated.