Controlled synthesis of monodisperse red-emitting α-CsPbI3 nanorods at the oil-water interface based on Cs4PbI6 nanocrystals

One-dimensional (1D) CsPbI 3 nanomaterials with long carrier lifetimes, high carrier transport efficiencies, and anisotropic optical properties show promising applications in lasers and photodetectors. In this study, monodisperse Cs 4 PbI 6 nanocrystals (NCs) (12.3 nm) were first synthesized by thermal injection. The addition of deionized water to this solution then induced the conversion of Cs 4 PbI 6 NCs into CsPbI 3 NCs, followed by their self-assembly into CsPbI 3 nanorods (NRs) with controllable aspect ratios. This process leverages the high solubility of CsI in water, which drives the decomposition of Cs 4 PbI 6 and the formation of CsPbI 3 NCs, which subsequently self-assembled and fused into CsPbI 3 NRs. CsPbI 3 NRs synthesized under the optimal reaction conditions were characterized by uniform size and regular morphology, with a diameter of 12.4 nm and length of 52.5 nm. XRD analysis shows that these monodisperse CsPbI 3 NRs, in contrast to 1D CsPbI 3 nanomaterials synthesized by the conventional thermal injection method, possess a typical cubic phase (α-phase) structure and exhibit good red light emission properties. Due to kinetic limitations during rapid nucleation at the nanoscale, the system preferentially forms the metastable α-CsPbI 3 , characterized by a low nucleation barrier and strong structural inheritance, rather than the thermodynamically stable δ-phase. Compared with NRs obtained under other reaction conditions, the optimal CsPbI 3 NRs demonstrate stronger fluorescence intensity and longer fluorescence lifetime. The CsPbI 3 NRs synthesized under the optimal conditions (2 mL water, 5 min) exhibit a strong first exciton absorption peak at 450 nm, a narrow photoluminescence emission peak at 695 nm, a lifetime as high as 239.9 ns, and a higher exciton binding energy (72.5 meV), ensuring efficient exciton emission at room temperature. Compared with NRs obtained under other reaction conditions, these optimally synthesized NRs demonstrate stronger fluorescence intensity and longer fluorescence lifetime. This work presents a reliable method for the controlled synthesis of 1D α-CsPbI 3 NRs, offering a theoretical and experimental foundation for the application of halide perovskite nanorods in high-performance optoelectronic devices.