Effective Design Strategy for Aggregation-Induced Emission and Thermally Activated Delayed Fluorescence Emitters Achieving 18% External Quantum Efficiency Pure-Blue OLEDs with Extremely Low Roll-Off

Jinshan Wang; Jianfeng Zhang; Cuifeng Jiang; Chuang Yao; Xinguo Xi

doi:10.1021/acsami.1c17449

Effective Design Strategy for Aggregation-Induced Emission and Thermally Activated Delayed Fluorescence Emitters Achieving 18% External Quantum Efficiency Pure-Blue OLEDs with Extremely Low Roll-Off

ACS Appl Mater Interfaces. 2021 Dec 8;13(48):57713-57724. doi: 10.1021/acsami.1c17449. Epub 2021 Nov 23.

Authors

Jinshan Wang¹, Jianfeng Zhang², Cuifeng Jiang¹, Chuang Yao³, Xinguo Xi¹

Affiliations

¹ School of Materials Science and Engineering, Yancheng Institute of Technology, Yancheng 224051, China.
² School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China.
³ Chongqing Key Laboratory of Extraordinary Bond Engineering and Advance Materials Technology (EBEAM), Yangtze Normal University, Chongqing 408100, China.

PMID: 34813274
DOI: 10.1021/acsami.1c17449

Abstract

High-color purity organic emitters with a simultaneous combination of aggregation-induced emission (AIE) and thermally activated delayed fluorescence (TADF) characteristics are in great demand due to their excellent comprehensive performances toward efficient organic light-emitting diodes (OLEDs). In this work, two D-π-A-structure emitters, ICz-DPS and ICz-BP, exhibiting AIE and TADF properties were developed, and both the emitters have narrow singlet (S₁)-triplet (T₁) splitting (ΔE_ST) and excellent photoluminescence (PL) quantum yields (Φ_PL), derived from the distorted configurations and weak intra/intermolecular interactions, suppressing exciton annihilation and concentration quenching. Their doped OLEDs based on ICz-BP provide an excellent electroluminescence external quantum efficiency (η_ext) and current efficiency (η_C) of 17.7% and 44.8 cd A^-1, respectively, with an η_ext roll-off of 2.9%. Their nondoped OLEDs based on ICz-DPS afford high efficiencies of 11.7% and 30.1 cd A^-1, with pure-blue emission with Commission Internationale de l'Éclairage (CIE) coordinates of (0.15, 0.08) and a low roll-off of 6.0%. This work also shows a strategy for designing AIE-TADF molecules by rational use of steric hindrance and weak inter/intramolecular interactions to realize high Φ_PL values, fast reverse intersystem crossing process, and reduced nonradiative transition process properties, which may open the way toward highly efficient and small-efficiency roll-off devices.

Keywords: AIE; TADF; high color purity; low efficiency roll-off; molecular construction strategy; pure-blue emitters.