Spontaneous decoration of ionic compounds at perovskite interfaces to achieve 23.38% efficiency with 85% fill factor in NiOX-based perovskite solar cells

Inorganic hole transport materials, particularly NiO, have shown considerable promise in boosting the efficiency and stability of perovskite solar cells. However, a major barrier to commercialization of NiO-based perovskite solar cells with positive-intrinsic-negative architectures is their direct contact with the absorbing layer, which can lead to losses of photovoltage and fill factor. Furthermore, highly positive under-coordinated Ni cations degrade the perovskite at the interface. Here, we address these issues with the use of an ionic compound (QAPyBF) as an additive to passivate defects throughout the perovskite layer and improve carrier conduction and interactions with under-coordinated Ni cations. Specifically, the highly electronegative inorganic anion [BF] interacts with the NiOx/perovskite interface to passivate under-coordinated cations (Ni). Accordingly, the decorated cells achieved a power conversion efficiency of 23.38% and a fill factor of 85.5% without a complex surface treatment or NiO doping.