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.