Dicarbocation-Doped Polycyclic Aromatic Hydrocarbons with Efficient Deep-Red Narrowband Electroluminescence.

Narrowband heteroaromatic emitters have garnered substantial attention for their applications in wide-color-gamut displays. Nevertheless, the design strategies for narrowband heteroaromatics in red-deep-red regions are limited. Here, we report novel dicarbocation-doped polycyclic aromatic hydrocarbon (PAH) emitters with deep-red narrowband emissions by embedding two positively charged carbocations (C) -positioned to four nitrogen atoms within an undecacyclic aromatic skeleton. This molecular design generates a distinct multiresonance effect with strong short-range charge transfer between C and nitrogen atoms to significantly reduce the energy gap to 1.80 ∼ 1.83 eV, realizing deep-red emission at 678 ∼ 684 nm with narrow full width at half maxima of 42 ∼ 44 nm (0.114 ∼ 0.117 eV). Remarkably, solution-processed organic light-emitting diodes utilizing the emitters achieved efficient deep-red narrowband electroluminescence with maximum external quantum efficiencies of 20.4% and CIE coordinates of (0.720, 0.280) that exceed the BT.2020 gamut standard for red emission. This study establishes multicarbocation-doped PAHs as a new paradigm for developing efficient, long-wavelength narrowband emitters in addition to conventional neutral heteroaromatic emitters.