Space-Confined Vertical\nGrowth of Large-Size Organic\nSemiconductor Single Crystals

Organic semiconductor single crystals (OSSCs) have garnered\nconsiderable\nattention because of their high charge mobility and atomic-scale smooth\nsurface. However, their large-size high-quality preparation remains\nchallenging due to the inevitable defects and limited growth speed\nbrought by traditional epitaxial growth. Here, we demonstrate a space-confined\nstrategy, named out-of-plane microspacing in-air sublimation (OPMAS),\nfor growing vertically millimeter-sized OSSCs in several minutes by\nrevolutionizing the heterogeneous epitaxial growth mode severely depending\non substrates into a spontaneous homogeneous growth mode free from\nsubstrates. The intrinsic driven force of this transformation is proved\nto be the change of surface energy, and the maximum size of crystals\nis thermodynamically dependent on the distance of the microspace.\nOPMAS has been proven to be suitable for preparing single crystals\nof various typical organic semiconductors. Numerous characterizations\nhave been conducted to prove the high quality and uniformity of the\nthus-produced OSSCs. In addition, the photoresponse of the prepared\nOSSCs is highly dependent on the illumination intensities, making\nit suitable for high-contrast Morse coding process, demonstrating\na stable switch ratio of about 3.3. This work provides a universal\nplatform for preparing large-sized OSSCs, advancing both fundamental\n(opto)electronic studies and a wide range of practical applications.