Li Man, Li Xin, Han Ying-Feng
Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, Xi'an Key Laboratory of Functional Supramolecular Structure and Materials, College of Chemistry and Materials Science, Northwest University, Xi'an, 710127, P. R. China.
Adv Mater. 2025 May;37(18):e2418324. doi: 10.1002/adma.202418324. Epub 2025 Mar 20.
Organic luminescent radicals possess considerable potential for applications in organic light-emitting diodes (OLEDs)-based visible light communication owing to their intrinsic advantages of nanosecond emission lifetimes and spin-allowed radiative transitions. However, the inherently narrow energy bandgap and multiple nonradiative channels of organic radicals make it difficult to achieve efficient green and blue light-emitting, which is not conducive to applying visible light communication in diverse fields. In this study, a series of carbon-centered radicals derived from N-heterocyclic carbenes are designed and synthesized, some of which exhibiting hybrid local and charge-transfer (HLCT) states that resulting in efficient green emission. The results of photophysical characterizations and theoretical calculations demonstrate that the luminescence efficiency is closely related to their emission states. This relationship inhibits the nonradiative channels while simultaneously opening the radiative channels of organic radicals exhibiting HLCT states but not those with locally excited states. Intriguingly, a high photoluminescence quantum yield value of up to 70.1% at 534 nm is observed, which is the highest among green light-emitting carbon-centered radicals reported to date. Based on this exceptional result, an OLED device is fabricated and achieved an external quantum efficiency of 8.8%. These results demonstrate its potential application in electroluminescent devices.
有机发光自由基因其纳秒级发射寿命和自旋允许的辐射跃迁等固有优势，在基于有机发光二极管（OLED）的可见光通信中具有相当大的应用潜力。然而，有机自由基固有的窄能带隙和多个非辐射通道使得实现高效的绿色和蓝色发光变得困难，这不利于可见光通信在不同领域的应用。在本研究中，设计并合成了一系列源自N-杂环卡宾的碳中心自由基，其中一些表现出杂化局域和电荷转移（HLCT）态，从而实现了高效的绿色发光。光物理表征和理论计算结果表明，发光效率与其发射态密切相关。这种关系抑制了非辐射通道，同时打开了呈现HLCT态而非局域激发态的有机自由基的辐射通道。有趣的是，在534nm处观察到高达70.1%的高光致发光量子产率值，这是迄今为止报道的绿色发光碳中心自由基中最高的。基于这一优异结果，制备了一种OLED器件，实现了8.8%的外量子效率。这些结果证明了其在电致发光器件中的潜在应用。
