Dr. Jeanne E. Pemberton
University of Arizona
Unraveling the Complexities of Degradation in Organic Electronic Materials
Organic semiconductors (OSCs) have shown considerable promise as active media in flexible, lightweight, low cost, and easily processed electronic devices. While their synthetic tenability provides numerous approaches to readily tune electronic properties for optimization of device characteristics and performance, a major barrier to wide-spread adaptation of OSC-based active layer materials is limited understanding and control over the physicochemical instability of the active layer materials involved. Here, instability is broadly defined as a decrease in material functionality and performance with time and can have mechanistic contributions that range over length scales from chemical bonds to conjugation length to microstructure, particularly in mixed or blended active material layers. In addition to intrinsic active layer instability, materially dissimilar electrical contacts in functional devices add another level of complexity to this problem, as these contact materials are chosen for efficient charge harvesting or injection and not for material compatibility or stability. Polarization of active materials during device operation may additionally alter degradation pathways and/or rates. Improvements in organic-based optoelectronic devices will not be possible without a molecular-level understanding of the physical and chemical interactions that drive instability in these complex hybrid systems. This presentation will highlight spectroscopic studies to elucidate the details of active layer instability at the length scales noted above through discussion of illustrative examples. Recent efforts to employ more advanced data analysis tools, including multivariate analysis and generalized 2D correlation spectroscopy, for a deeper understanding of these processes will be described, with the goal of developing a diagnostic probe of early-stage degradation in OSC-based devices.