Molecular design of DBA-type five-membered heterocyclic rings to achieve 200% exciton utilization for electroluminescence

Qi Sun; Yishi Wu; Yuanyuan Cui; Can Gao; Qi Ou; Deping Hu; Lu Wang; Yue Wang; Huanli Dong; Jianzhang Zhao; Chunfeng Zhang; Zhigang Shuai; Hongbing Fu; Qian Peng

doi:10.1039/D2MH00919F

Molecular design of DBA-type five-membered heterocyclic rings to achieve 200% exciton utilization for electroluminescence†

Qi Sun,

‡^a Yishi Wu,‡^d Yuanyuan Cui,^c Can Gao,^e Qi Ou,^a Deping Hu,^a Lu Wang,^a Yue Wang,

^c Huanli Dong,

^e Jianzhang Zhao,

^f Chunfeng Zhang,^g Zhigang Shuai,

*^a Hongbing Fu^d and Qian Peng

*^be

Author affiliations

* Corresponding authors

^a MOE Key Laboratory of Organic Optoelectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing, P. R. China
E-mail: zgshuai@tsinghua.edu.cn

^b School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, P. R. China
E-mail: qianpeng@ucas.ac.cn

^c College of Chemistry, Jilin University, Changchun 130012, P. R. China

^d Department of Chemistry, Capital Normal University, Beijing 100048, P. R. China

^e Institute of chemistry, Chinese Academy of Sciences, Beijing, P. R. China

^f School of Chemical Engineering, Dalian University of Technology, 2 Ling Gong Road, Dalian 116024, P. R. China

^g School of Physics, Nanjing University, Nanjing, China

Abstract

Achieving high exciton utilization is a long-cherished goal in the development of organic light-emitting diode materials. Herein, a three-step mechanism is proposed to achieve 200% exciton utilization: (i) hot triplet exciton (T₂) conversion to singlet S₁; (ii) singlet fission from S₁ into two T₁; (iii) and then a Dexter energy transfer to phosphors. The requirement is that S₁ should lie slightly lower than or close to T₂ and twice as high as T₁ in energy. For this, a scenario is put forward to design a series of donor-bridge-acceptor (DBA) type molecules with 2E(T₁) ≤ E(S₁) < E(T₂), in which the Baird-type aromatic pyrazoline ring is used as a bridge owing to its stabilized T₁ (1.30–1.74 eV) and different kinds of donors and acceptors are linked to the bridge for regulating S₁ (2.35–3.87 eV) and T₂ (2.44–3.96 eV). The ultrafast spectroscopy and sensitization measurements for one compound (TPA-DBPrz) fully confirm the theoretical predictions.

Materials Horizons

Molecular design of DBA-type five-membered heterocyclic rings to achieve 200% exciton utilization for electroluminescence†

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Molecular design of DBA-type five-membered heterocyclic rings to achieve 200% exciton utilization for electroluminescence

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