Intense Organic Afterglow Enabled by Molecular Engineering in Dopant-Matrix Systems

Xun Li; Guangming Wang; Jiuyang Li; Yan Sun; Xinjian Deng; Kaka Zhang

doi:10.1021/acsami.1c20331

Intense Organic Afterglow Enabled by Molecular Engineering in Dopant-Matrix Systems

ACS Appl Mater Interfaces. 2022 Jan 12;14(1):1587-1600. doi: 10.1021/acsami.1c20331. Epub 2021 Dec 28.

Authors

Xun Li¹, Guangming Wang¹, Jiuyang Li¹, Yan Sun¹, Xinjian Deng¹, Kaka Zhang¹

Affiliation

¹ Key Laboratory of Synthetic and Self-Assembly Chemistry for Organic Functional Molecules, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, People's Republic of China.

PMID: 34963292
DOI: 10.1021/acsami.1c20331

Abstract

We report intense dopant-matrix afterglow systems with an afterglow efficiency (Φ_AG) of 47% and an afterglow lifetime (τ_AG) of 1.3 s. Luminescent difluoroboron β-diketonate (BF₂bdk) dopants and their deuterated counterparts are designed with naphthalene and carboxylic acid groups. After doping into benzoic acid (BA) matrices, room-temperature afterglow brightness and afterglow duration of the BF₂bdk-BA materials have unexpectedly been found to reach the levels of those at 77 K, which indicates that hydrogen bonding between BF₂bdk and BA, as well as the deuteration technique, can reduce k_nr + k_q of BF₂bdk triplets to very small values even at room temperature. Detailed studies reveal that the BF₂bdk possesses typical ¹ICT characters in the S₁ state and distinct ³LE composition in the T₁ state, and thus shows a high Φ_ISC and a small k_P to obtain a high Φ_AG and a long τ_AG. Besides, triplet-triplet annihilation has been found in the dopant-matrix system at high doping concentrations to further increase Φ_AG.

Keywords: afterglow; organic materials; phosphorescence; triplet excited states; triplet−triplet annihilation.