Suppressing Redox Reactions at the Perovskite‐Nickel Oxide Interface with Zinc Nitride to Improve the Performance of Perovskite Solar Cells

Abstract For p‐i‐n perovskite solar cells (PSCs), nickel oxide (NiO x ) hole transport layers (HTLs) are the preferred interfacial layer due to their low cost, high mobility, high transmittance, and stability. However, the redox reaction between the Ni ≥3+ and hydroxyl groups in the NiO x and perovskite layer leads to oxidized CH 3 NH 3 + and reacts with PbI in the perovskite, resulting in a large number of non‐radiative recombination sites. Among various transition metals, an ultra‐thin zinc nitride (Zn 3 N 2 ) layer on the NiO x surface is chosen to prevent these redox reactions and interfacial issues using a simple solution process at low temperatures. The redox reaction and non‐radiative recombination at the interface of the perovskite and NiO x reduce chemically by using interface modifier Zn 3 N 2 to reduce hydroxyl group and defects on the surface of NiO x . A thin layer of Zn 3 N 2 at the NiO x /perovskite interface results in a high Ni 3+ /Ni 2+ ratio and a significant work function (WF), which inhibits the redox reaction and provides a highly aligned energy level with perovskite crystal and rigorous trap‐passivation ability. Consequently, Zn 3 N 2 ‐modified NiO x ‐based PSCs achieve a champion PCE of 21.61%, over the NiO x ‐based PSCs. After Zn 3 N 2 modification, the PSC can improve stability under several conditions.