Spray Printing Single Crystal Electronics

Atoms like to combine in lattice-like arrays that we call crystals. Atoms and molecules often combine with each other based on how their outer electron shell is filled. When there is a good match and conditions permit, a crystal “seed” can form and then add outer layers to it, growing a crystal. Often, many crystals form simultaneously and then combine with other crystals. But, where the individual crystals combine with other crystals, as the boundary conditions vary, so do the characteristics across the boundary. Under optimal conditions, either larger single crystals or pristine single crystals can form. Single crystal structures exhibit great strength in fibers, and improved performance in semiconductors and optical applications.

Crystallization is often promoted by phase changes, such as cooling liquids and allowing gaseous forms to solidify. Spray printing of semiconductor inks may offer a new form of producing single crystals with well defined boundaries. Because this can be accomplished at normal pressures and room temperature, it may have significant implications for mass production of specific electronic components.

Spray printing of organic semiconducting single crystals – [nature.com]

Single-crystal semiconductors have been at the forefront of scientific interest for more than 70 years, serving as the backbone of electronic devices. Inorganic single crystals are typically grown from a melt using time-consuming and energy-intensive processes. Organic semiconductor single crystals, however, can be grown using solution-based methods at room temperature in air, opening up the possibility of large-scale production of inexpensive electronics targeting applications ranging from field-effect transistors and light-emitting diodes to medical X-ray detectors. Here we demonstrate a low-cost, scalable spray-printing process to fabricate high-quality organic single crystals, based on various semiconducting small molecules on virtually any substrate by combining the advantages of antisolvent crystallization and solution shearing. The crystals’ size, shape and orientation are controlled by the sheer force generated by the spray droplets’ impact onto the antisolvent’s surface. This method demonstrates the feasibility of a spray-on single-crystal organic electronics.

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