Korean researchers hold out promise of ultra-low cost flexible display

January 24, 2013 // By Christoph Hammerschmidt
A research team of the Ulsan National Institute of Science and Technology (UNIST) has developed a way to make paper-like flexible display devices closer with remarkably low cost. Polymer-based electronic circuits are expected to open up possibilities for ubiquitous electronics including flexible displays, but also RFID tags and large-area sensors.

The characteristics of these organic thin film transistors(OTFTs) depend on organic semiconductors. There are two types of polymer-organic semiconductors: ambipolar and unipolar ones, the researchers say.

Circuits made from unipolar semiconductors are high in electricity resistance, and low in mobility and stability. Through a combination of improved semiconducting polymer design and fabrication techniques, progress has been achieved in enhancing the charge carrier mobility of organic thin-film transistors. However, novel ambipolar polymers with better performance and further advances in fabrication processes are still required to truly realize practical organic integrated circuits.

The research team developed a dithienyl-diketopyrrolopyrrole (TDPP) and selenophene containing polymer with hybrid siloxane-solubilizing groups ( PTDPPSe-Si). A synergistic combination of rational polymer backbone design, side-chain dynamics, and solution processing affords an enormous boost in ambipolar TFT performance. The resulting polymer exhibited unprecedentedly high hole and electron mobilities in solution-sheared polymer films. “To the best of our knowledge, these are the highest recorded hole and electron mobilities for organic- or polymer-based ambipolar TFTs reported to date” said the research team.