Recent Advances in Cation-Engineered A₃BX₆ Metal Halide Perovskite for Enhanced Radiative Transition

A₃BX₆ perovskites, a family of vacancy-ordered structures, exhibit diverse luminescence behaviors upon photon, electron, and high-energy excitation, primarily originating from intrinsic self-trapped excitons or dopant-induced electronic transitions. Upon B-site cation engineering, ns² cations tune intrinsic luminescence, whereas transition-metal and rare-earth dopants activate characteristic d-d, d-f, and f-f transitions, enriching A₃BX₆ optical diversity. The tunable crystal structure and electronic configuration endow A₃BX₆ perovskites with exceptional versatility for photoluminescence, electroluminescence, and scintillation applications. This review systematically elucidates how B-site chemistry modulates the structure-property-application relationships in this material family. P-block B-site A₃BX₆ perovskites exhibit high photoluminescence efficiency, broadband emission, and strong ultraviolet absorption, enabling applications in high-sensitivity photodetectors (1.23 × 10¹² Jones), information encryption, and white light-emitting diodes. In comparison, rare-earth-based A₃BX₆ perovskites enable high-efficiency electroluminescent devices, featuring deep-blue light-emitting diode with an external quantum efficiency of 7.9%. Moreover, they exhibit superior scintillation performance, including high x-ray light yield (88,800 ph/MeV), low x-ray detection limit (63 nGy/s), and notable γ-ray response under ¹³⁷Cs excitation (47,000 ph/MeV; 4.0% energy resolution). These insights highlight the pivotal role of B-site cation engineering in tailoring luminescence mechanisms and enabling multifunctional A₃BX₆ perovskites for photonic and radiation applications.