Scaling Up Principles for Solution-Processed Organic Single-Crystalline Heterojunctions

The development of advanced organic devices has already broken the limit of one-component material constitution, seeking for integration of multiple components to achieve new features. It is well-known that organic single crystals have highly ordered molecular packing, which directly bounds up with electrical and optoelectrical behaviors. Thus, organic heterojunctions composed of binary organic single crystals are able to exhibit superior electrical/optoelectrical performance as well as novel functions. Intimate junction contact, high coverage, and well-aligned morphology are demanded in large-scale organic single-crystalline heterojunctions for realizing subsequent device fabrication and further practical production. So far, fabrication of organic single-crystalline heterostructures without destroying the single crystallinity of both crystals has been extremely challenging, due to the fragile nature of weak noncovalent molecule-molecule interactions in organic single crystals. Therefore, the long-standing discrepancy will exist between the urgent need of organic single-crystalline heterojunctions with desired morphology and enormous challenges in feasible large-scale preparation. Along with continuous developments in recent literature, we try to provide two principle frameworks including two-step crystallization and one-step crystallization methods as possible solutions.