Controlling the performance of semiconducting polymers for printed electronics (Invited paper)
Organic materials are forming a new basis for the manufacture of electronic devices, such as displays, where they will be used as substrates and active materials. The electrical performance of thin-film transistors, TFTs, formed with printable semiconducting polymers is rapidly approaching that of amorphous silicon. Flexible substrates present unique challenges for the fabrication and design of printed electronics. We will discuss the interplay between the demands of practical fabrication methods and our ability to control the electrical performance of semiconducting polymers. For example, the roughness of many dielectrics on flexible substrates approaches the length scale of the molecular dimensions of many semiconducting material and has a strong influence on the field-effect mobility of polymeric transistors. X-ray scattering data shows that ordering in films of semicrystalline polythiophenes is nucleated from the surface suggesting that roughness can affect molecular ordering. The performance of transistors is also strongly affected by chemical functionalities at the surface of the gate dielectric. For example, hydrophilic surfaces generally produce TFTs with lower field-effect mobilities than hydrophobic ones. This result sets a limit on the types of surfaces that can be printed onto for high performance polymeric TFTs. We will discuss our methods to control surface energies to achieve high quality printing while maintaining good electrical properties.
Chabinyc, M. Controlling the performance of semiconducting polymers for printed electronics. (Invited paper) 2007 MRS Spring Meeting; 2007 April 9-13; San Francisco; CA.