Thin Film Printing
The goal of this research is to develop a scalable platform for cost-effective, high-resolution additive printing of patterned organic and inorganic thin films. Our research utilizes polymeric materials that are molded into patterned surfaces to enable precise pick-up and delivery of small portions of material down to sub-100 nm dimensions (vertical and lateral). Unlike other patterning methods, our contact printing makes efficient use of printed material, is scalable to large-area and flexible substrates, and is not limited in resolution by light diffraction or material diffusion.
Within this project, we have recently developed a family of polyurethane-acrylates (PUA) stamp materials that can be used in a number of contact printing applications. We demonstrate that the surface energy of PUA polymers can be controlled chemically, producing stamps with tunable polarity and eliminating the need to apply releasing coatings or to adjust stamping kinetics to facilitate material transfer. To demonstrate the general nature of the proposed materials, PUA polymers were used in contact printing of organic molecules and organic thin films.
We also demonstrated that PUA stamps can be used to pattern electroluminescent layers of organic light emitting diodes (OLEDs). We showed that electroluminescent thin films can be printed with high uniformity and resolution (800 nm pixel lines). We also showed that the performance of the printed devices can be improved via post-printing thermal annealing, and that the external quantum efficiency of the printed devices is comparable with the efficiency of the vacuum-deposited OLEDs. Our results suggest that the PUA-based contact printing can be used as an alternative to the traditional shadow mask deposition, permitting replication of OLED displays with >15,000 dpi resolution.
J Li, L Xu, CW Tang, AA Shestopalov, ACS Applied Materials & Interfaces, 2016, 8(26), 16809–16815
J Li, L Xu, S Kim, AA Shestopalov, Journal of Materials Chemistry C, 2016, 4(19), 4155–4165
NSF ECCS 1530540