*Review* **Organic Semiconductor Micro/Nanocrystals for Laser Applications**

**Javier Álvarez-Conde 1,2 , Eva M. García-Frutos 1,\* and Juan Cabanillas-Gonzalez 2,\***


**Abstract:** Organic semiconductor micro/nanocrystals (OSMCs) have attracted great attention due to their numerous advantages such us free grain boundaries, minimal defects and traps, molecular diversity, low cost, flexibility and solution processability. Due to all these characteristics, they are strong candidates for the next generation of electronic and optoelectronic devices. In this review, we present a comprehensive overview of these OSMCs, discussing molecular packing, the methods to control crystallization and their applications to the area of organic solid-state lasers. Special emphasis is given to OSMC lasers which self-assemble into geometrically defined optical resonators owing to their attractive prospects for tuning/control of light emission properties through geometrical resonator design. The most recent developments together with novel strategies for light emission tuning and effective light extraction are presented.

**Keywords:** organic molecules; single crystals; molecular packing; lasers; optical resonators
