An Organic Single Crystal Laser Beyond 900 nm Based on Synergetic Excited‐State Intramolecular Proton and Charge Transfer

ABSTRACT Organic single crystal materials are attracting growing interest for laser applications due to their high purity, low defect density, and large stimulated emission cross‐sections. However, the development of organic single crystal lasers operating in the near‐infrared (NIR, 780–2500 nm) range remains challenging, primarily limited by the energy‐gap law. Herein, we propose a molecular design strategy that synergizes excited‐state intramolecular proton transfer and charge transfer within a single molecule. This combination establishes an efficient four‐level system and significantly narrows the emission energy gap via barrierless energy decay. Following this strategy, we designed and synthesized a donor–acceptor–donor type molecule, 2,6‐bis(4‐(dimethylamino)phenyl)‐1,5‐dihydroxyanthracene‐9,10‐dione (AP‐DHAQ) which exhibits excellent crystallizability. 1D AP‐DHAQ microrods with regular morphology and high crystal quality were easily prepared through a facile solution self‐assembly method, serving simultaneously as optical resonators and gain media. Based on these microrods, NIR lasing at 940 nm was achieved with a low threshold of 27.9 µJ cm −2 , which, to the best of our knowledge, represents the longest wavelength reported for metal‐free organic single crystal lasers. This work advances organic single‐crystal lasers toward previously inaccessible spectral regions.