Nat. Mater.: Achieving small singlet–triplet energy gaps in polycyclic heteroaromatic emitters

Authors：

Rajat Walia^1,2#, Xin Xiong^1,2#, Xiao-Chun Fan^1,2#, Ting-Feng Chen¹, Hui Wang¹, Kai Wang^1,3*,Yi-Zhong Shi⁴, Xun Tang⁵,Jean-Luc Bredas⁶, Chihaya Adachi⁵*,Xian-Kai Chen^1,3* & Xiao-Hong Zhang^1,7*

Institutions：

¹Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, P. R. China

²Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou, P. R. China

³State Key Laboratory of Bioinspired interfacial Materials Science, Soochow University, Suzhou, P. R. China

⁴School of Materials Science and Engineering, Suzhou University of Science and Technology, Suzhou, P. R. China

⁵Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, Fukuoka, Japan

⁶Department of Chemistry and Biochemistry, The University of Arizona, Tucson, AZ, USA

⁷Jiangsu Key Laboratory of Advanced Negative Carbon Technologies, Soochow University, Suzhou, P. R. China

Abstract：

In polycyclic heteroaromatic (PHA) emitters, which possess great potential for application in ultrahigh-definition displays, the origin of a small singlet–triplet energy gap (ΔE_S1T1) and its relationship with the molecular structure still remain poorly established. Here we derive an effective expression for ΔE_S1T1, in which ΔE_S1T1 positively depends on 2K_HL (where K_HL is the exchange energy between the highest occupied molecular orbital and the lowest unoccupied molecular orbital (LUMO)) and on the energy gap between LUMO and LUMO+1 (ΔE_{LUMO–LUMO+1}). This expression for ΔE_S1T1 is validated over a series of 100 reported PHA emitters. It allows us to easily identify various molecular design approaches for managing ΔE_S1T1 by synergistically regulating 2K_HL and ΔE_{LUMO–LUMO+1}. The proof-of-concept PHA molecules were synthesized and characterized to further confirm the validity of this expression for ΔE_S1T1. Overall, our work provides a physical picture to not only modulate ΔE_S1T1 in emerging PHA emitters but also design and screen such materials with small ΔE_S1T1.

IF：

38.5

Link：

https://doi.org/10.1038/s41563-025-02309-4