Fast Organic Vapor Phase Deposition of Thin Films in Light-Emitting Diodes

Ultrasmooth Organic Films Via Efficient Aggregation Suppression by a Low-Vacuum Physical Vapor Deposition

Organic thin films with smooth surfaces are mandated for high-performance organic electronic devices. Abrupt nucleation and aggregation during film formation are two main factors that forbid smooth surfaces. Here, we report a simple fast cooling (FC) adapted physical vapor deposition (FCPVD) method to produce ultrasmooth organic thin films through effectively suppressing the aggregation of adsorbed molecules. We have found that thermal energy control is essential for the spread of molecules on a substrate by diffusion and it prohibits the unwanted nucleation of adsorbed molecules. FCPVD is employed for cooling the horizontal tube-type organic vapor deposition setup to effectively remove thermal energy applied to adsorbed molecules on a substrate. The organic thin films prepared using the FCPVD method have remarkably ultrasmooth surfaces with less than 0.4 nm root mean square (RMS) roughness on various substrates, even in a low vacuum, which is highly comparable to the ones prepared using conventional high-vacuum deposition methods. Our results provide a deeper understanding of the role of thermal energy employed to substrates during organic film growth using the PVD process and pave the way for cost-effective and high-performance organic devices.

Printable Organic Electronic Materials for Precisely Positioned Cell Attachment

Over the past 3 decades, there has been a vast expansion of research in both tissue engineering and organic electronics. Although the two fields have interacted little, the materials and fabrication technologies which have accompanied the rise of organic electronics offer the potential for innovation and translation if appropriately adapted to pattern biological materials for tissue engineering. In this work, we use two organic electronic materials as adhesion points on a biocompatible poly(p-xylylene) surface. The organic electronic materials are precisely deposited via vacuum thermal evaporation and organic vapor jet printing, the proven, scalable processes used in the manufacture of organic electronic devices. The small molecular-weight organics prevent the subsequent growth of antifouling polyethylene glycol methacrylate polymer brushes that grow within the interstices between the molecular patches, rendering these background areas both protein and cell resistant. Last, fibronectin attaches to the molecular patches, allowing for the selective adhesion of fibroblasts. The process is simple, reproducible, and promotes a high yield of cell attachment to the targeted sites, demonstrating that biocompatible organic small-molecule materials can pattern cells at the microscale, utilizing techniques widely used in electronic device fabrication.