Flexible organic crystals: From rational design to applications

Abstract Flexible organic crystals (FOCs) represent an innovative category of organic crystalline materials distinguished by their remarkable ability to undergo elastic deformation or bending when subjected to external forces, all while maintaining the integrity of their crystalline order. This challenges the conventional perception that organic crystals are inherently brittle and fragile. The studies indicate that FOCs can maintain their functional characteristics during the mechanical processes, underscoring their remarkable adaptability and their promising potential for innovative applications in diverse fields, including electronics, optics, and materials science. Besides, FOCs can be designed to respond to various stimuli including light, heat, or mechanical stress, enhancing their versatility in smart materials and actuator applications. This adaptability spans a wide range of uses, from micro‐scale devices to larger and more complex systems. Although rapid advancement has been achieved in the field, there is still a need for a comprehensive understanding of the material design and development routes for FOCs. This perspective provides a concise yet comprehensive summary of the current understanding of FOCs. It explores the origins of their flexibility and the mechanisms underlying deformations, such as elastic bending. Additionally, it illustrates typical examples of FOCs, with a particular emphasis on the optoelectronic changes that occur in deformed crystals, which can aid in the development of FOCs and broaden their practical applications effectively.