High-Efficiency Circularly Polarized Light-Emitting Diodes Based on Chiral Metal Nanoclusters

Abstract

Circularly polarized light-emitting diodes (CP-LEDs) are critical for next-generation optical technologies, ranging from holography to quantum information processing. Currently deployed chiral luminescent materials, with their intricate synthesis and processing and limited efficiency, are the main bottleneck for CP-LEDs. Chiral metal nanoclusters (MNCs) are potential CP-LED materials, given their ease of synthesis and processability as well as diverse structures and excited states. However, their films are usually plagued by inferior electronic quality and aggregationcaused photoluminescence quenching, necessitating their incorporation into host materials; without such a scheme, MNC-based LEDs exhibit external quantum efficiencies (EQEs) < 10%. Herein, we achieve an efficiency leap for both CP-LEDs and clusterbased LEDs by using novel chiral MNCs with aggregation-induced emission enhancement. CP-LEDs using enantiopure MNC films attain EQEs of up to 23.5%. Furthermore, by incorporating host materials, the devices yield record EQEs of up to 36.5% for both CP-LEDs and cluster-based LEDs, along with electroluminescence dissymmetry factors (|g EL |) of around 1.0 × 10 −3 . These findings open a new avenue for advancing chiral light sources for next-generation optoelectronics.

Ligand engineering of circularly polarized luminescence inversion and enhancement for chiral Ag6 nanoclusters

“…30,31 Thus, chiral nanoclusters became an excellent candidate for constructing CPL-active materials with both high QY and tuneable supramolecular chirality. 32,33 In general, the chirality of nanoclusters mainly originates from the following three chiral sources: (a) intrinsic chirality of the inorganic metal cores with asymmetrical stacking, (b) twisted arrangement of achiral ligands on the surface of the cluster core, and (c) induced chirality from the chiral ligand on the surface of the cluster. 34–37 Chiral induction from organic ligands is the most convenient method for the preparation of chiral metal nanoclusters since it is easy to control the chirality by tuning the R/ S -configuration of chiral ligands and endowing the obtained nanocluster with amplified chirality performances especially for the CPL emissive intensity.…”

Recent Advances in Electroluminescent Metallic Nanoclusters: From Materials to Devices

“…Enantiopure R / S -4-benzylthiazolidine-2-thione ( R / S -BTT) featuring bidentate ligands were used to stabilize chiral copper-gold alloy MNCs through N-Cu and S-Au coordination, respectively, resulting in Cu 2 Au 2 (R/S-BTT) 4 characteristic of a quasi-rhombic geometry with an average Cu–Au distance of 2.847 Å shorter than the sum of their van der Waals radii (3.06 Å), which indicated the participation of metallophilic interactions . Owing to their rigid structures, Cu 2 Au 2 (R/S-BTT) 4 revealed AIE enhancement on their green emissions, giving rise to PLQY values of 94 and 89% in film for R- and S-enantiomers, in comparison to 7 and 13% in solution, respectively.…”