Inhibiting ion migration in strontium-lead halide perovskite for pure-blue emission: a first-principle and...

Bromide-chloride mixed perovskites have garnered significant attention as a direct and efficient material for achieving pure-blue emission. However, the complex problem of halide migration in mixed halide perovskites presents a significant obstacle to achieving stable electroluminescence (EL) spectra. Here, we investigate the mechanism of partially replacing the B-site Pb²⁺ with the non-toxic Sr²⁺ to achieve pure-blue emission based on first principles. The ion mobility activation energy of Sr²⁺ is 1.23 eV, which is an order of magnitude greater than that of halogens. Meanwhile, the incorporation of Sr²⁺ triples the activation energy for halogen migration. Furthermore, the halide defect formation energy increases from 4.75 eV to 5.62 eV, thereby reducing ion migration channels. Transient absorption spectroscopy demonstrates that suppressing the ion mobility pathway and enhancing ion mobility activation energy promotes the perovskite film to exhibit excellent spectral stability under laser pumping. Our work provides insights for the development of highly stable and eco-friendly perovskite devices.