Continuous-wave organic laser enabled by monolayer molecular crystal.

Organic lasers, by virtue of their inherent flexibility, cost-effectiveness, and tunable wavelength, offer potential applications in wearable optoelectronics, biocompatible sensing, and full-colour flexible display. However, continuous-wave (CW) solid-state organic lasers have been obstructed owing to the nonradiative losses induced by triplet exciton accumulation as well as the photo-thermal degradation of organic materials under continuous optical excitations. Here, we have accomplished room-temperature CW organic lasing by employing a monolayer organic molecular crystal (MOMC) as the gain medium. The J-aggregate configuration in the MOMC induces super-radiant emission with an ultrashort radiative lifetime, which outcompetes the intersystem crossing (ISC) timescale, thus effectively suppressing the triplet exciton accumulation. Furthermore, the thermal stability of the MOMC is enhanced by encapsulating it within a hexagonal boron nitride microdisk, which serves as both the optical resonator and the thermal management material. Consequently, we obtain CW organic lasing at room temperature, featured by the reduced emission linewidth, threshold behaviour, as well as the build-up of linear polarization and coherence. Our findings break the long-term challenge in the organic semiconductor community and pave the way for the practical applications of organic lasers.