Highly Luminescent Hybrid Europium(II) Bromide for Electrically Driven Light‐Emitting Diodes

Abstract Substituting toxic lead (Pb ²⁺ ) with bivalent lanthanide (Ln ²⁺ ) ions in metal halide perovskites has garnered increasing interest for the development of high‐performance and environmentally friendly optoelectronics. Among the common Ln ²⁺ ions, europium (Eu ²⁺ ) stands out as particularly attractive because it can produce pure blue emission with a narrow linewidth. However, due to the susceptibility of Eu ²⁺ to oxidation, most Eu ²⁺ ‐based compounds experience reduced luminescence efficiency and require protection in an inert gas environment. Herein, this study presents an organic–inorganic low‐dimensional Eu ²⁺ ‐bromide metal cluster, (BTEA)EuBr ₃ (BTEA = benzyltriethylammonium), which demonstrates strong antioxidant activity and exhibits a high photoluminescence quantum yield of ≈88%. It attributes these qualities to the shorter Eu─Eu bond length in their faced‐shared structures, which enhances the interchain Eu─Eu coupling, thereby leading to stronger covalency between neighboring Eu and their structural stability. Electrically‐driven light‐emitting diodes (LEDs) fabricated with (BTEA)EuBr ₃ produce the characteristic emission of Eu ²⁺ , demonstrating their potential use in next‐generation blue‐light‐emitting devices.