Sn‐Doped Nb₂O₅Films as Effective Hole‐Selective Passivating Contacts for Crystalline Silicon Solar Cells

Carrier‐selective contacts (CSCs) in crystalline silicon (c‐Si) solar cells have attracted great attention due to suppressing contact region recombination and achieving higher conversion efficiency. Among transition metal oxides for CSCs, niobium oxide (Nb₂O₅) is considered as an attractive candidate for electron‐selective contact due to its excellent passivation properties and small conduction band offsets with c‐Si. Nevertheless, the performance of c‐Si solar cells employing Nb₂O₅contact layer has not been explored yet. Herein, the carrier selectivity of solution‐processed Nb₂O₅films is investigated for c‐Si. Interestingly, Nb₂O₅exhibits high electron‐blocking performance and low contact resistivities with p‐Si. The ultra‐thin SiO_xinterlayer formed by UV–O₃pretreatment further reduces the contact resistivities and increases minority carrier lifetime due to the improved contact interface. The Sn⁴⁺doping improves the work function of Nb₂O₅to induce larger upward band bending at c‐Si surface, thus enhancing the hole selectivity. As a result, p‐type c‐Si solar cells with solution‐processed Nb₂O₅hole‐selective contact layer have achieved the highest power conversion efficiency of 18.4%, with a high‐thermal stability superior to the typical hole transport layers. This work first demonstrates the exceptional hole selectivity of Nb₂O₅, which shows very promising applications in high‐efficiency c‐Si solar cells.