Single-crystalline or highly crystallized semiconductor materials enjoys their superior electrical performances from the long-range ordering and low defect density. Optimized substrates are crucial in the epitaxial growth of such semiconductor materials, such as single-crystalline silicon for silicon membrane homoepitaxy, sapphire substrate for gallium nitride crystal growth, and copper foil for chemical vapor deposition of graphene. The electrical/optical performance of the crystals is largely predetermined by the substrate quality, and cannot be easily altered after the crystal growth. This situation is equally applied to organic semiconductor crystals (OSCs) in optoelectronic applications.
The motivation of this research is to decouple the substrate limitations from high-quality crystal growth. A novel transfer method is developed for organic thin-films to solve the contradiction between good substrate wettability and good interface stability. Highly crystallized organic crystals are firstly deposited on a smooth rigid substrate, and then transferred onto lyophobic but inert surfaces (e.g. ODPA/AlOx) with the help of orthogonal polymers and solvents. The OFETs based on transferred OSCs show remarkable carrier mobility up to 12 cm2V-1s-1 on the high-k dielectric with an operating voltage less than 4 V. Without the limitations from the original substrates, these devices exhibit excellent bias stability and ultra-flexibility (bending radius < 100 um). More importantly, the transfer technique enables the possibilities of large-area expanding of highly-crystallized OSCs by multiple transfer steps, and allows the study the device physics in multi-stacking or supperlattices of OSCs. It is believed that the transfer technique would have great application potentials in implantable bio-medical sensors, shape-adaptive electronic skins, and flexible display panels.