Organic semiconductor single crystals (OSSCs), which possess the inherent merits of long-range order, low defect density, high mobility, structural tunability and good flexibility, have garnered significant attention in the organic optoelectronic community. Past decades have witnessed the explosive growth of OSSCs. Despite numerous conceptual demonstrations, OSSCs remain in the early stages of implementation for applications that require high integration and multifunctionality. The commercialization trend of organic optoelectronic devices is driving the development of highly integrated OSSCs. Therefore, timely tracking of material requirements, crystallization demands, and key technologies for high integration, along with exploring their limitations and potential pathways, will provide critical guidance during this pivotal transition period. From the perspective of materials properties, multifunctional materials, such as ambipolar charge transport materials, high mobility emission materials and others, aiming at high integration, deserve our attention, and the material design rules are carefully discussed in the first section. Following this, we delve into the controllable growth of large-scale OSSCs based on crystallization thermodynamics and kinetics. Key technologies for achieving high integration are then discussed, with an emphasis on methods for growing wafer-scale organic single crystals and patterning single crystalline arrays. Subsequently, we outline the cutting-edge optoelectronic applications based on OSSCs, including organic logic circuits, electroluminescent displays, and image sensors. Moreover, explicitly recognizing as yet limitations and prospects on the road to 'lab-to-fab' transitions for OSSCs is crucial. Thus, we conclude by offering an objective assessment of key limitations and potential, encompassing aspects such as uniformity, integration density, stability, and driving capability, providing an instructive projection for future advancements.