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

Inorganic hole transporting materials (HTMs), particularly NiOX, have shown significant promise in boosting the efficiency and stability of perovskite solar cells. However, a major challenge facing NiOX-based p-i-n perovskite solar cells (PSCs) is their direct contact with the absorber layer, which can lead to photovoltage and filling factor losses. Additionally, under-coordinated Ni cations can react with the perovskite and cause damage. In this work, we address these issues by using an ionic compound (QAPyBF4) as a perovskite additive to passivate the entire perovskite layer and interact with under-coordinated Ni cations. Our results show that the introduction of QAPyBF4 significantly enhances the performance and stability of NiOX-based PSCs. Specifically, the decorated cells achieved a power conversion efficiency (PCE) of 23.38% and a fill factor (FF) of 85.46%, with no need for complicated surface treatment or NiOX doping. The QAPyBF4 compound passivates the buried NiOX/perovskite interface, effectively reducing photovoltage and filling factor losses. Moreover, the [BF4]‒ component of the compound interacts with under-coordinated Ni cations to prevent their negative impact on the perovskite layer. Overall, our study proposes a simple and effective approach to optimize the performance and stability of NiOX-based PSCs through the use of ionic compound additives. Our findings suggest that addressing buried NiOX/perovskite interface issues and under-coordinated Ni cation considerations are critical in achieving high-performance and stable NiOX-based PSCs.