Non-conventional exciplex system by leveraging zero-radius of intramolecular energy transfer mechanism: Seamless integration of p-host and fluorescent dopant for highly efficient OLEDs

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-07, Vol.492, p.152371, Article 152371
• Main Authors: Na Song, You, Bae Park, Bu, Lee, Hakjun, Kang, Sunwoo, Pyo Hong, Wan, Yun Oh, Hyoung, Kim, Taekyung
• Format: Article
• Language: English
• Subjects: Blue fluorescent; Fused emitter; Organic light-emitting diodes; Zero radius of intramolecular energy transfer mechanism; ZETPLEX
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.152371

•p-host and fluorescent dopant was seamlessly integrated into a single molecule.•Non-conventional exciplex formed between fused p-host and n-host.•ZETPLEX, an extremely efficient energy transfer within fused p-host and n-host. A multi-component emissive layer (EML) composed of a mixture of p- and n-type hosts and a dopant is a widely used structure in organic light-emitting diodes (OLEDs) due to its high efficiency and operational stability. However, multi-component EML devices impose limitations such as difficulty in accurately controlling the mixing ratio and profiles in the manufacturing process, high costs, and complexity in the photophysical properties of the components. In this paper, a p-type host fused with a blue fluorescent dopant, 5,9-di([1,1′-biphenyl]-2-yl)-2′-(9H-carbazole-9-yl)3,7-dimethyl-5,5a,5a1,9,9a,16a-hexahydrospiro[5,9-diaza-16b-boraindeno[2,1-b]naphtho[1,2,3-fg]anthracene-11,9′-fluorene] (DABNA-Spiro-Cz), was designed and successfully synthesized to construct a novel EML structure. Completely fused within DABNA-Spiro-Cz, the p-type host and blue fluorescent dopant can independently perform their respective roles. An exciplex is formed between n-type host and p-type host unit in the DABNA-Spiro-Cz molecule and its energy is effectively transferred to the blue fluorescent dopant unit in DABNA-Spiro-Cz. In other words, a degree of freedom is earned from a conventional 3-component exciplex-dopant system. A high external quantum efficiency of 14.9 % was achieved thanks to “zero-radius of intramolecular energy transfer in exciplex (ZETPLEX)” system, which is completely non-conventional and novel. We believe the ZETPLEX mechanism opens a new era of designing emissive materials and paves a new way of constructing a novel EML and device architecture for highly efficient OLEDs.