Performance and Thermal Stability of an a-Si:H/TiOx/Yb Stack as an Electron-Selective Contact in Silicon Heterojunction Solar Cells

Abstract

Low contact resistivity (ρc) and low recombination current density at the metallized area (J0,metal) are the key parameters for an electron-selective contact in solar cells, and an i-a-Si:H/TiOx/low work function metal (ATOM) structure could satisfy these criteria. In this work, to achieve strong downward band bending, an Yb (Φ = 2.5–2.6 eV)/Ag stack is used. Moreover, the impact of (1) substrate topography (flat or textured), (2) TiOx thickness, and (3) Ti precursor (TTIP vs TDMAT) on the ATOM contact performance is investigated. The results show that the ATOM contact is relatively insensitive to the surface topography and to the Ti precursors (TTIP or TDMAT) used for the atomic layer deposition (ALD) of TiOx. However, the TiOx thickness has a significant impact on the ρc and marginally on the J0,metal of the ATOM contact. For all topography cases and Ti precursors, 1 nm thick TiOx results in the lowest ρc value, most likely due to EF,metal depinning. In the silicon heterojunction solar cell, this ATOM c...