Metal-Filled Porous Silicon for Plasmonic Light Trapping in Solar Cell Applications: A Comparative Finite Element Study of Ag, Au, and Cu

Crystalline silicon (c-Si) solar cells currently dominate with commercial module efficiencies of 22-24% and laboratory records similar to 27% for single junction devices. These values are constrained by optical losses, including insufficient light trapping within the device architecture. In this study we report a finite element analysis (FEA), carried out in COMSOL Multiphysics RF Module (v.5.3a), of a one-dimensional porous silicon array (1D PSiA) with pores filled by silver (Ag), gold (Au), and copper (Cu) in a c-Si substrate, targeting enhanced light trapping through surface plasmon polaritons (SPPs) and localized surface plasmon resonance (LSPR). Pore width (w) was swept from 50 to 600 nm at a fixed periodicity (Lambda) of 700 nm under transverse-magnetic (TM) illumination. Far-field transmission spectra reveal a Fano-resonance dip at 703-720 nm governed by the structural periodicity. Full-width at half-maximum (FWHM) and near-field electric-field norm (E-Norm) analysis identify w = 200 nm as the critical coupling width for Ag (E-Norm peak 0.0044 a.u.) and w = 200-250 nm for Au and Cu (0.0045 and 0.0040 a.u.). Coupling efficiencies (eta) at w = 200 nm reach 97.2%, 96.4%, and 95.4% for Ag, Au, and Cu, respectively, saturating above 99% for w >= 250 nm; relative transmission (T-rel) peaks near 0.029 a.u. at w = 250 nm before declining sharply. A four-way correlation of FWHM, E-Norm, eta, and T-rel is consistent with the optimum pore widths correspond to roughly one-third of the structural periodicity, offering a computationally validated geometric design rule for pore-confined plasmonic solar cell fabrication.