Solvated Palladium (II) Complexes for Efficient and Stable All-Inorganic CsPbI₂Br Perovskite Solar Cells

We present a novel approach to enhance the efficiency and stability of inorganic CsPbI₂Br based perovskite solar cells (PSCs) through the incorporation of a solvated palladium (Pd) complex, PdBr₂(PhCN)₂, into perovskite precursor inks (PhCN = benzonitrile). This modification not only stabilizes the α-phase of CsPbI₂Br perovskite owing to Pd²⁺ 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 PdBr₂(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 PdBr₂(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.