Emissive organic crystals and device applications.

Emissive organic crystals represent a rapidly advancing frontier in materials science, offering a unique platform that merges the superior optoelectronic characteristics of crystalline order with high-efficiency light emission. This review comprehensively surveys the field, from the fundamental molecular design principles and photophysical mechanisms, such as aggregation-induced emission, thermally activated delayed fluorescence, and room-temperature phosphorescence, to the advanced engineering of crystal packing and morphology. The unique light-matter interactions inherent to these crystalline materials, which underpin applications in optical waveguiding and stimulated emission (lasing), are elaborated upon. The review further discusses device integration, highlighting recent progress in organic light-emitting transistors, single-crystal light-emitting diodes, sensors and display arrays. Finally, the review outlines the existing challenges and future opportunities for these crystalline materials in next-generation photoelectronic technologies.