CPOS Seminar: "Understanding Structure-Property Relationships in P(NDI2OD-T2): Insights from In-Situ GIWAXS and FET Studies"

Speaker: Linjing Tang, Postdoctoral Researcher, UC Santa Barbara, Materials Department - Chabinyc Group

Ph.D., Department of Materials Science and Engineering, Monash University, Melbourne, Australia (Prof. Chris McNeill)

P(NDI2OD-T2) is a benchmark donor-acceptor type semiconducting polymer that has been extensively studied due to its excellent electronic properties and intriguing self-assembly characteristics. Previous studies identified two different polymorphs of P(NDI2OD-T2) formed at different annealing temperatures using high-resolution TEM. However, deeper structural information about these two polymorphs remains to be investigated, which is crucial to understand the effect of thermal annealing on film microstructure and electronic properties of this polymer.

This study employs in-situ grazing incidence X-ray scattering (GIWAXS) to capture these two polymorphs during heating, revealing differences in their thermal expansion coefficients and crystallite growth rates. Through a comprehensive comparison of previous studies with our findings, we propose a new perspective that might reconcile previously reported seemingly conflicting experimental observations regarding the structure-property relationship of this material.

Finally, we investigated the FET mobility of N2200 as a function of annealing temperature, which shows a transition temperature at 200℃ that is lower than the 230℃ transition temperature determined from GIWAXS results but consistent with the transition temperature identified by UV–vis absorption spectroscopy. This observation suggests that charge transport in P(NDI2OD-T2) is not limited to the crystalline regions but also derives significant contributions from the less ordered amorphous regions.