Luminescent organic radicals have garnered increasing attention owing to their versatile applications in sensing, imaging, and organic light-emitting diodes (OLEDs), attributed to their unique emission properties originating from the doublet spin state. However, the natural narrow bandgap of organic free radicals typically limits their emission to the long-wavelength region. Designing luminescent organic radicals with short-wavelength emission remains a significant challenge. Herein, a series of carbon-centered radicals with short-wavelength emission (383–476 nm) by combining N-heterocyclic carbenes with various polycyclic aromatic hydrocarbons (PAHs) (2-naphthyl, 2a^I and 2b^I; 2-phenanthryl, 2a^II and 2b^II; 2-anthryl, 2a^III and 2b^III; 3-phenanthryl, 2a^IV and 2b^IV). Theoretical calculations reveal that the introduction of PAHs significantly increases the ΔE_D2-D1 in 2a^I–III and 2b^I–III compared to that in phenyl-derived radical congeners. Consequently, the internal transition from D2 to D1 is impeded, leading to a high yield of D2 emission and a suppressed Kasha’s rule, thereby overcoming the limitations imposed by their narrow bandgap. For 2a^IV and 2b^IV, despite a moderately large ΔE_D2-D1 value, the ΔE_D3-D1 value exceeds 1 eV, indicating that their emission likely originates from the D3 state. Furthermore, we utilized 2a^III and 2b^III as emissive materials in OLEDs, resulting in blue emissions with external quantum efficiencies of 7.5% and 6.5%, respectively.

发光有机自由基因其在传感、成像和有机发光二极管（OLED）方面的广泛应用而受到越来越多的关注，这归因于其源自双态自旋态的独特发射特性。然而，有机自由基的天然窄带隙通常限制其发射到长波长区域。设计具有短波长发射的发光有机自由基仍然是一个重大挑战。在此，通过将N-杂环卡宾与各种多环芳烃（PAH）（2-萘基，2a ^I 和2b <结合在一起，形成一系列具有短波长发射（383-476 nm）的碳中心自由基。 b1>；2-菲基，2a ^II 和2b ^II ；2-蒽基，2a ^III 和2b ^III ；3-菲基，2a ^IV 和 2b ^IV )。理论计算表明，与苯基衍生的自由基同系物相比，PAHs的引入显着增加了2a ^I–III 和2b ^I–III 中的ΔE _D2-D1 。因此，从 D2 到 D1 的内部跃迁受到阻碍，导致 D2 发射的高产率和 Kasha 规则受到抑制，从而克服了窄带隙带来的限制。对于2a ^IV 和2b ^IV ，尽管ΔE _D2-D1 值较大，但ΔE _D3-D1 值超过1 eV，表明它们的发射可能源自 D3 态。此外，我们利用2a ^III 和2b ^III 作为OLED中的发射材料，产生蓝光发射，外量子效率分别为7.5%和6.5%。