From Nanocrystals to Nanowires: The Control of Cs₂AgBiBr₆ Morphology by Cesium Oleate

Double perovskite materials are promising lead-free alternatives due to their low toxicity and high stability. However, their large indirect bandgap limits optical performance. Morphology control offers an effective enhancement strategy. Here, cesium oleate (Cs-OA) and bromotrimethylsilane (TMS-Br) were injected into an oleic acid-free precursor. The OA present reacts with oleylamine (OAm) to form oleylammonium oleate (OAmH⁺·OA^-), which, synergistically with OAm, enhances Ag⁺ and Bi³⁺ solubility. TMS-Br then provides bromide, triggering rapid nucleation of Cs₂AgBiBr₆ nanoclusters. Under thermodynamic control, these grow into uniform nanocrystals. Over time, multiple nanowires self-assemble and fuse into one-dimensional structures. Time-resolved photoluminescence shows a prolonged exciton lifetime of 19.0 ns, indicating low defect density. Temperature-dependent PL confirms a large exciton binding energy (61.1 meV), weak nonradiative recombination, and strong luminescence potential. The nanowires also exhibit excellent stability, retaining over 90% of their PL intensity after 90 days at room temperature.