Organic molecular crystal with a high ultra-deep-blue emission efficiency of ∼85% for low-threshold laser

Organic crystal with a high emission efficiency and excellent spectral stability is crucial for constructing low-threshold deep-blue organic laser. Here, we synthesized an organic lasing molecule (BPhDPF) with a steric diarylfluorene as the core building block, the single crystal of which has ultra-deep-blue emission with the photoluminescence quantum yield (PLQY) as high as 84.9%, as well as short lifetime and super-stable emission. Meanwhile, C-H ⋯ π interactions are easily observed in single crystal structure, contributing to the formation of BPhDPF polyhedral microcrystals by self-organize in solution. Interestingly, the intermolecular coupling and exited state were well inhibited by the large steric hindrance group at 9-position and 2-/7- flexible side-chain, which is critical to laser applications. Finally, the deep-blue emission organic laser was obtained with a peak located at 418 nm and very low threshold of Pth = 1.62 μJ cm−2. A novel organic lasing molecule has been developed, offering helpful information for further investigating organic lasers. [Display omitted] •A polyhedral crystal is obtained with an extremely high ultra-deep-blue emission efficiency of ∼85% and a CIE of (016, 0.04), associated with the confinement of single-molecular exciton in crystal.•Both molecular crystal and pristine spin-coated film present an ultra-sable emission efficiency and spectral stability.•Polyhedral crystals display a deep-blue lasing behavior at ∼418 nm with an extremely low threshold of 1.62 μJ cm−2.