Solvated Palladium (II) Complexes for Efficient and Stable All‐Inorganic CsPbI ₂ Br Perovskite Solar Cells

ABSTRACT We present a novel approach to enhance the efficiency and stability of inorganic CsPbI ₂ Br based perovskite solar cells (PSCs) through the incorporation of a solvated palladium (Pd) complex, PdBr ₂ (PhCN) ₂ , into perovskite precursor inks (PhCN = benzonitrile). This modification not only stabilizes the α‐phase of CsPbI ₂ Br perovskite owing to Pd ²⁺ ions, which were found to be incorporated into the perovskite structure at the B‐site, but also effectively improves the perovskite film morphology through the removal of benzonitrile molecules during annealing. Further systematic study reveals that the addition of PdBr ₂ (PhCN) ₂ results in a better matched energy‐level alignment and reduced charge carrier recombination compared to the unmodified material. As a result, the optimized device enables an efficiency of 16.4% with an open‐circuit voltage ( V _OC ) of 1.27 V, which outperforms the control device (14.1%, 1.19 V). The device with PdBr ₂ (PhCN) ₂ shows substantially enhanced environmental and operational stabilities, retaining ≈75% and 90% of their initial PCEs after 500 h aging, respectively. This study demonstrates the potential of B‐site engineering via solvated precursors as an effective route toward stable and efficient inorganic perovskite photovoltaics.