Boosting Stimulated Emission via a Hydrogen-Bonded Co-Crystallization Approach in Molecular Crystals

Stimulated emission (SE) of organic π-conjugated molecule in solid state remains a significant challenge, mainly involving the mode of molecular stacking that invariably alters the photo-physical processes. Herein, we successfully realized stimulated emission in molecular crystals using a hydrogen-bonded co-crystallization strategy. Two hydrogen-bonded co-crystals, obtained from 1,4-bis-p-cyanostyrylbenzene (CNDSB) and two types of co-formers, can boost stimulated emission and show decent amplified spontaneous emission (ASE), whereas the parent CNDSB crystal is not SE-active. Crystal structural analysis demonstrated that the co-crystallization eliminated excimer formation. The resulting higher k_r and shorter excited lifetime led to a larger stimulated emission cross-section, which benefited to the occurrence of ASE. Simultaneously, the uniaxial arrangements along the long axis of co-crystal together contributed to highly polarized emission. This system presents very rare evidence of boosting stimulated emission by binary co-crystallization, which enriches our insights into organic solid-state lasers.