Transition Metal Ions‐Doped Lead‐Free Halide Double Perovskites for Stable Light Emission: Optical Properties and Optoelectronic Applications

Abstract Lead‐free double perovskites (LFDP) have attracted considerable attention due to their remarkable optoelectronic characteristics, which include tunable bandgaps spanning the entire visible spectrum, high photoluminescence quantum yields (PLQY), and wide emission bandwidths. The incorporation of transition metal ions into lead‐free double perovskites, as an efficient method for tailoring optical properties, is crucial for both the foundational research and practical applications in devices such as light‐emitting diodes (LEDs), anti‐counterfeiting, temperature sensors, and X‐ray scintillators. In this review, the recent progress in the design of transition metal ion‐doped lead‐free double perovskites is summarized, and briefly introduce the strategies for the effective doping of several representative transition metal ions in lead‐free double perovskites. The manipulation of the optical properties of lead‐free double perovskites through transition metal ion doping, focusing on enhanced stability, increased luminescent efficiency, tuning of emission bands, and luminescence lifetimes are highlighted. In conclusion, the challenges and perspectives in this dynamic area of research are addressed.