Aggregation‐Driven Thorough Cascaded Proton Transfer Process Targeting Ultralow‐Threshold Near‐Infrared Organic Single‐Crystal Lasers

Abstract

ABSTRACT Near‐infrared (NIR) organic solid‐state lasers (OSSLs) are technologically crucial in lasing communication systems, yet they still suffer from the high threshold and low optical gain due to the limited exciton utilization rate. Excited‐state double proton transfer (ESDPT) processes of organic gain materials offer promising gain mechanisms for NIR OSSLs due to the favored six‐electronic‐level energy systems and large red‐shifted stimulated emission. Herein, we proposed a novel strategy aimed at modulating the ESDPT process through aggregation effect, where crystallization‐enhanced thorough cascaded ESDPT process facilitates the exciton utilization rate and thus enables an ultralow lasing threshold. Impressively, the strong J ‐type coupling of 4260 cm −1 in DDMC single‐crystal microwires effectively stabilizes TB* level by lowering excited state energy, supporting a thorough ESDPT process. Consequently, all excited electrons decaying by radiative transitions participate in stimulated emission, enabling a high‐gain six‐level energy system with efficient population inversion density (∆ N ). Activated by this efficient energy‐level system, the NIR single‐crystal lasing at ∼870 nm was successfully realized with a record‐low threshold of 486 nJ cm −2 . Our work elucidates the fundamental mechanism underlying aggregation effects on ESDPT gain materials, offering effective strategy to enhance the exciton utilization rate for low‐threshold and high‐gain NIR OSSLs, and even the electrically‐pumped NIR OSSLs in the future.