Multifunctional zero-dimensional hybrid halide for multiscale buried interface planarization in perovskite solar cells

Abstract

The buried interface between electron transport layer (ETL) and perovskite absorber often induce the awful properties of perovskite film such as interfacial defects, trenched structure and ion migration, hindering improving efficiency and stability of perovskite solar cells (PSCs). Here, we present a multiscale planarized interface regulation (MPIR) strategy by introducing π-conjugated zero-dimensional (0D) metal halide, BPP₂MnBr₄ (BPP⁺ = C₂₅H₂₂P⁺), as multifunctional interlayer on SnO₂. The π-conjugated multi-phenyl framework enables strong coupling with adjacent functional layers, while the 0D configuration provides quantum confinement and structural robustness. Theoretical and experimental analyses reveal that BPP₂MnBr₄ increases the formation energy of non-photovoltaic phase (δ-FAPbI₃), thus improving phase purity. Additionally, buried interface modified by BPP₂MnBr₄ flattens grain boundary trenches to release residual stress for perovskite film. Benefiting from MPIR achieves a high efficiency of 25.88 %, and good stability for maintaining 92.0 % of initial efficiency after 1000 h of continuous light irradiation in N₂ without encapsulation of perovskite devices. Besides, the resulted solar module with an active area of 25.74 cm² (6.5 cm$\times$6.5 cm $\times$9 sub-cells) exhibits a PCE of 22.37 % with excellent uniformity. These results establish π-conjugated 0D metal halides as multifunctional interlayers capable of simultaneously improving structural robustness and operational reliability in perovskite photovoltaics.