Toward High-Performance Pure-Green Tandem Organic Light-Emitting Diodes by Employing Barrier-Free Strategies in the Charge Generation Layer

Qishen Chen; Zhiheng Wang; Yukang Li; Zhiping Yan; Heming Zhang; Xuming Hu; Xiaoxian Song; Hai Bi; Yue Wang

doi:10.1021/acsami.4c19993

Toward High-Performance Pure-Green Tandem Organic Light-Emitting Diodes by Employing Barrier-Free Strategies in the Charge Generation Layer

ACS Appl Mater Interfaces. 2024 Dec 24. doi: 10.1021/acsami.4c19993. Online ahead of print.

Authors

Qishen Chen¹, Zhiheng Wang^{1

2}, Yukang Li³, Zhiping Yan¹, Heming Zhang¹, Xuming Hu¹, Xiaoxian Song^{1

2}, Hai Bi^{1

2}, Yue Wang^{2

4}

Affiliations

¹ Department of Materials Science and Technology, Ji Hua Laboratory, Foshan, Guangdong Province 528200, P. R. China.
² Jihua Hengye Electronic Materials Co. Ltd., Foshan, Guangdong Province 528200, P. R. China.
³ Guangdong University of Technology, Guangzhou, Guangdong Province 510006, P. R. China.
⁴ State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, P. R. China.

PMID: 39719061
DOI: 10.1021/acsami.4c19993

Abstract

Charge generation layers (CGLs) play crucial roles in determining the electroluminescence (EL) performance of tandem organic light-emitting diodes (OLEDs). However, acquiring negligible voltage drops across the CGL unit and high-efficiency multiplications remains challenging. Here, we propose barrier-free strategies to compose a high-performance p-i-n type CGL intermediate by introducing a Yb/HI-9 modification at the heterojunction and a novel n-dopant, Yb:1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene (mdPPhen), as the n-CGL. Mechanism analysis confirms that the Yb/HI-9 modification efficiently eliminates the intrinsic energy mismatch at the n-CGL/p-CGL interface, while the lowest unoccupied molecular orbital (LUMO) of the n-dopant can be aligned to the electron transport layer of adjacent EL units, creating improved electron transport. Consequently, the resulting 2-EL unit tandem OLEDs exhibited no voltage drops across the CGL intermediate with excellent efficiency multiplications. Notably, the barrier-free CGL strategy worked efficiently in the sensitized fluorescence tandem OLED with low operating voltage, extremely high efficiency (current efficiency of 267.2 cd/A, external quantum efficiency of 62.6%), and operational stability (95% of the initial luminance at 3000 cd/m², T95 of 4713 h) with pure-green emission (CIEy coordinate of over 0.68), showing the best tandem OLED among reported CGLs to satisfy commercial demands.

Keywords: barrier-free modifications; charge generation layer; sensitized fluorescence; tandem organic light-emitting diode; ytterbium-phenanthroline complexes.