A Novel Ultra‐Low Work Function TbF_x for High Efficiency Dopant‐Free Silicon Solar Cells

Abstract The ability of carrier selective contact is mainly determined by the surface passivation and work function for dopant‐free materials applied in crystalline silicon (c‐Si) solar cells, which have received considerable attention in recent years. In this contribution, a novel electron‐selective material, lanthanide terbium trifluoride (TbF_x), with an ultra‐low work function of 2.4 eV characteristic, is presented, allowing a low contact resistivity (ρ_c) of ≈3 mΩ cm². Additionally, the insertion of ultrathin passivated SiO_x layer deposited by PECVD between TbF_x and n‐Si resulted in ρ_c only increase slightly. SiO_x/TbF_x stack eliminated fermi pinning between aluminum and n‐type c‐Si (n‐Si), which further enhanced the electron selectivity of TbF_x on full‐area contacts to n‐Si. Last, SiO_x/TbF_x/Al electron‐selective contacts significantly improves the open circuit voltage (V_oc) for silicon solar cells, but rarely impacts the short circuit current (J_sc) and fill factor (FF), thus champion efficiency cell achieved approaching 22% power conversion efficiency (PCE). This study indicates a great potential for using lanthanide fluorides as electron‐selective material in photovoltaic devices.