Anti-Heavy-Atom Effect Boosts Electroluminescence in Copper Cluster-Based LEDs
Fei-Fan Wang1, Tao-Tao Xia1, Zi-Cong Dong1
1Henan Key Laboratory of Crystalline Molecular Functional Materials, Key Laboratory of Special Functional Molecular Materials (Zhengzhou University), Ministry of Education, Pingyuan Laboratory, Zhengzhou University, Zhengzhou, China.
Angewandte Chemie (International Ed. in English)
|May 18, 2026
Summary
The anti-heavy-atom effect improves light-emitting diode (LED) performance. Replacing a heavy atom with a lighter one in copper clusters significantly boosts electroluminescence efficiency by reducing non-radiative losses.
Area of Science:
- Materials Science
- Chemistry
- Solid State Physics
Background:
- The heavy-atom effect is crucial for intersystem crossing and phosphorescence but its role in light-emitting diode (LED) electroluminescence is not well understood.
- A clear molecular-level understanding of how heavy atoms influence LED performance is lacking.
Purpose of the Study:
- To investigate the impact of the heavy-atom effect on electroluminescence (EL) efficiency in copper(I) clusters.
- To explore a strategy for enhancing LED performance by manipulating the heavy-atom effect.
Main Methods:
- Synthesized a pair of nearly isostructural copper(I) clusters, Cu4S and Cu4Se, differing only by a single central atom substitution (S vs. Se).
- Fabricated and characterized non-doped and thermally activated delayed fluorescence (TADF) host-based LED devices using both Cu4S and Cu4Se emitters.
- Conducted systematic studies to analyze photoluminescence (PL) characteristics, external quantum efficiencies (EQEs), concentration quenching, charge transport, and trap-state density.
Main Results:
- Cu4S and Cu4Se showed similar photoluminescence (PL) properties and non-doped device EQEs (5.8% vs. 5.5%).
- Cu4S-based devices consistently outperformed Cu4Se devices across different host matrices, achieving a maximum EQE of 20.9% in TADF hosts compared to 12.9% for Cu4Se.
- The lighter-atom cluster (Cu4S) demonstrated superior resistance to concentration quenching, enhanced charge transport, and reduced trap-state density, mitigating heavy-atom-induced non-radiative losses.
Conclusions:
- Single-atom variations within the cluster core significantly impact EL efficiency, demonstrating an anti-heavy-atom effect.
- Exploiting the anti-heavy-atom effect offers a novel strategy for enhancing LED performance by minimizing non-radiative decay pathways.
- The findings provide molecular-level insights into optimizing emitters for efficient electroluminescence in LED devices.
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