Cluster Light‐Emitting Diodes Containing Copper Iodine Cube with 100 % Exciton Utilization Using Host‐Cluster Synergy

Abstract

Clusters combine the advantages of organic molecules and inorganic nanomaterials, which are promising alternatives for optoelectronic applications. Nonetheless, recently emerged cluster light-emitting diodes require further excited state optimization of cluster emitters, especially to reduce population of the clustercentered triplet quenching state ( 3 CC). Here we report that redox-active ligands enhance reverse intersystem crossing (RISC) of Cu 4 I 4 cluster for triplet-to-singlet conversion, and thermally activated delayed fluorescence (TADF) host can provide an external RISC channel. It indicates that the complementarity between TADF host and cluster in RISC transitions gives rise to 100 % triplet conversion efficiency and complete singlet exciton convergence, rendering 100fold increased singlet radiation rate constant and tenfold decreased triplet non-radiation rate constant. We achieve a photoluminescence quantum yield of 99 % and a record external quantum efficiency of 29.4 %.

Electroluminescent Clusters

“…(c) Device configuration and energy‐level diagram, and (d) EQE‐luminance relationship of CLEDs based on 28 . Reproduced with permission [19] . Copyright 2023, Wiley‐VCH.…”

“…Consequently, 27 ‐based devices realized the maximum EQE of 19.5 %, which was the first example of CLEDs with the state‐of‐the‐art efficiencies comparable to all kinds of planar light‐emitting devices (Figure 5c). TADF characteristics of 28 were further enhanced by doubled 9,9‐dimethyl‐acridine (DMAC) groups, therefore the maximum EQE of its devices was slightly improved to 21.4 % [19] . More importantly, when using 10‐(4‐((4‐(9H‐carbazol‐9‐yl)phenyl)sulfonyl)‐phenyl)‐9,9‐dimethyl‐9,10‐dihydroacridine (CzAcSF) with TADF feature instead of conventional ambipolar hosts, the EQE of CzAcSF: 28 dramatically increased to 29.4 % close to the theoretical maximum, which is comparable to the best results of all kinds of light‐emitting devices (Figure 5d).…”

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

“…30,31 These factors require the integration of MNCs into host materials, which have shown promise in partially mitigating and ameliorating these issues, leading to an increase in the reported maximum external quantum efficiency (EQE) up to 29.4%. 32 Nevertheless, in the majority of reported studies, the incorporation of at least 80 wt % host materials remains a prerequisite to ensure sufficient electrical conductivity of the emissive layer. 29,32,33 On the other hand, the EQEs of LEDs based on pure MNCs, without host material integration, remain below 10%, 32,34−36 1a.…”

“…The presence of excessive ligands which leads to inferior electrical conductivity and electronic film quality adversely affects charge injection and transport within the LEDs . Moreover, when MNCs aggregate or come into proximity, their excited states can interact, resulting in nonradiative energy transfer and quenching of the luminescence. , These factors require the integration of MNCs into host materials, which have shown promise in partially mitigating and ameliorating these issues, leading to an increase in the reported maximum external quantum efficiency (EQE) up to 29.4% . Nevertheless, in the majority of reported studies, the incorporation of at least 80 wt % host materials remains a prerequisite to ensure sufficient electrical conductivity of the emissive layer. ,, On the other hand, the EQEs of LEDs based on pure MNCs, without host material integration, remain below 10%, ,− underscoring the need to surmount MNC-LED challenges to harness their potential for high-efficiency optoelectronics.…”

“…32 Nevertheless, in the majority of reported studies, the incorporation of at least 80 wt % host materials remains a prerequisite to ensure sufficient electrical conductivity of the emissive layer. 29,32,33 On the other hand, the EQEs of LEDs based on pure MNCs, without host material integration, remain below 10%, 32,34−36 1a. As shown in Figure S1, the crystallographic analysis reveals a distinctive planar tetranuclear structure composed of a Cu−Au alloy, protected by R/S-BTT ligands.…”