Analysis of Inverse Lifetime Curves of TaOx Electron-Selective Contacts for Si Solar Cells

The analysis of Auger-corrected inverse minority-carrier lifetime as a function of excess carrier concentration can impart information about many crucial solar cell material properties including: emitter saturation current density (J(o)), surface recombination velocity (SRV), Shockley-Read-Hall (SRH) recombination in the bulk, trap density, band bending, surface Fermi-level pinning, and bandgap narrowing. This work demonstrates TaOx as a potential electron selective contact and passivation layer on silicon. Increasing TaOx thickness reduces the measured upper limit of effective surface recombination velocity (S-eff,S-UL). The minimum S-eff,S-UL is 55 cm/s for CZ n-Si / 30 nm TaOx interfaces. S-eff,S-UL increases for Si / TaOx / ITO structures due to unfavorable band bending.