Role of additive-assisted texturing on surface morphology and interface defect density in silicon heterojunction solar cells

Abstract

The efficiency of silicon heterojunction (SHJ) solar cells depends critically on c-Si surface topography and defect passivation. This study optimizes the formation of random pyramids using chemical additives in the texturization solution, achieving pyramids with optimal base and vertex angles and a low surface reflectance of ∼ 10.51%. Interface defect states (D_it) and surface lifetime (τ_surf) were analysed at various cell fabrication stages. The deposition of i-a-Si: H layers on both sides of the textured wafer reduced D_it to ∼ 8.5 × 10⁸ eV^− 1cm^− 2 with τ_surf ∼ 4.9 ms indicating good chemical passivation of the defects. Adding the carrier-selective layers (p-a-Si: H and n-nc-Si: H) further reduced D_it to ∼ 7.0 × 10⁸ eV^− 1cm^− 2 and enhanced τ_surf to ∼ 21.0 ms. However, sputtering-induced plasma damage during ITO deposition increased D_it to ∼ 11.8 × 10⁸ eV^− 1cm^− 2, lowering τ_surf to ∼ 3.3 ms. Optimized c-Si surface conditioning led to a power conversion efficiency of ∼ 22.4% and an open-circuit voltage of ∼ 727 mV from an SHJ cell. Device dark current-voltage analysis also provided insights into the charge carrier recombination dynamics.