Bimetallic Nanocluster‐Based Light‐Emitting Diodes With High External Quantum Efficiency and Saturated Red Emission

Abstract Self‐emissive atomically precise metal nanoclusters (NCs) are emerging as promising emissive layer material for next‐generation light‐emitting diodes (LEDs), thanks to their solid‐state luminescence, well‐defined structures, photo/thermal stability, low toxicity, and unique excited‐state properties. However, achieving high external quantum efficiency (EQE) in solid‐state NCs remains a formidable challenge. In this study, a highly stable bimetallic gold‐copper NC forming [Au 2 Cu 6 (Sadm) 6 (DPPEO) 2 ] stabilized with 1‐adamantanethiol (HSadm) and 1,2‐bis(diphenylphosphino)ethane (DPPE) as the primary and secondary ligands, respectively is reported. Single‐crystal X‐ray diffraction and spectroscopic analyses suggest that the as‐synthesized NC contains one phosphine bound to gold and the second phosphine has oxidized to phosphine oxide (P═O). The presence of such P═O moieties in the NC facilitated C─H···O interactions along with C─H··· π and H···H interactions between ligands, promoting rapid crystallization. Due to the exceptional photo/thermal stability and enhanced solid‐state photoluminescence quantum yield (PLQY), [Au 2 Cu 6 (Sadm) 6 (DPPEO) 2 ] NC is utilized to fabricate the NC‐based LED (NC‐LED) via the solution‐processed technique, without using any additional host materials. The fabricated NC‐LED shows a maximum brightness of 1246 cd m −2 and an EQE of 12.60% with a pure red emission ≈668 nm. This EQE value coupled with saturated pure red emission is the best among solution‐processed and non‐doped NC‐LEDs, suggesting the enormous potential of the NCs for electro‐optical devices.