In this project, state-of-the-art scanning probe microscopy (SPM) will be employed to advance current understanding of structure-property relationships in organic semiconductors. Specifically, new SPM techniques under development at the University of Minnesota will allow correlation of structural and electrostatic complexity in polycrystalline organic semiconductor films. This information will be critical for understanding the impact of structure on charge transport and for defining strategies to improve the performance of organic semiconductors in plastic electronics applications. In terms of human resources, this project will result in the training of graduate students, undergraduates, and postdocs in the materials science of organic semiconductors, thin films, structure characterization, electronics, and scanning probe microscopy. The PIs will also undertake outreach and education activities, including the development of new undergraduate laboratory exercises emphasizing materials characterization by SPM, and the organization and hosting of SPM workshops at the University of Minnesota for representatives from local industry. These significant outreach efforts will expand the impact of the proposal beyond the specific scientific accomplishments.
In this project, high resolution scanning probe microscopes (SPMs) will be used to image films of so-called "organic semiconductors". These materials are essentially plastics that conduct electricity and can be used to fabricate flexible electronic devices such as light-emitting diodes (LEDs), transistors, and solar cells. The new microscopy studies will determine the link between electrical performance of the films and film structure on lengths scales spanning 10 nanometers to 1 millimeter. This kind of microscopy information is critical to understanding how to improve the organic semiconductor films for plastic electronics applications. In terms of human resources, this project will result in the training of graduate students, undergraduates, and postdoctoral fellows in the materials science of organic semiconductors, thin films, structure characterization, electronics, and scanning probe microscopy. The PIs will also undertake outreach and education activities, including the development of new undergraduate laboratory exercises emphasizing materials characterization by SPM, and the organization and hosting of SPM "hands-on" workshops at the University of Minnesota for representatives from local industry. These significant outreach efforts will expand the impact of the proposal beyond the specific scientific accomplishments.
This grant from NSF funded the research and training of three PhD students in materials science and engineering at the University of Minnesota. The research projects of all three students focused on understanding the molecular level structure of thin films of a new class of semiconductors called organic or plastic semiconductors. Organic semiconductors are used in commercial products like OLED displays and they are also being considered for use in new flexible electronics products such as RFID tags. The students on this project were interested in understanding the structure of organic semiconductor thin films and how the structure related to performance in devices. They used very high magnification microscopes (atomic force microscopes) to image the films as a function of the film growth conditions. They observed important defects in these films (such as displocations), that if controlled or mitigated, could lead to dramatic performance improvements of the materials. Their work was written up and published in 10 peer-reviewed scientific articles. Two more articles are being prepared at the time this report was submitted. One of the students was received a presitigious award from the Materials Research Society for his thesis work funded by this award. Two of the students have completed their PhDs and have gone on to work in industry (Dow Chemical and Seagate Technology). The third student is still working on her doctoral research which continues the work described here.
