Non-technical Abstract Organic semiconductor materials hold exceptional promise in a number of existing and emerging technologies including optoelectronics, thermoelectrics, bioelectronics, and energy harvesting and storage applications. Degradation of these materials during use is a major issue in the commercial implementation of organic semiconductors. These degradation pathways are thought to be a complex combination of effects resulting from exposure to small amounts of gases and moisture in the ambient atmosphere as well as ultraviolet radiation. With the support of the Solid State and Materials Chemistry program, this foundational effort allows development of sophisticated, state-of-the-art spectroscopic tools based on the interaction of light and electrons with these materials to identify the chemical pathways that accompany degradation, leading to better solutions to solve this complicated problem. This inherently interdisciplinary effort has substantial broader impact through the professional development of the graduate students involved. Graduate students conduct a portion of their dissertation research in the laboratory of the other Principal Investigator, as well as complete a 6-week internship at Next Energy Technologies, Inc.
Solid-state organic semiconductor materials are the essential active components of a variety of existing and emerging technologies, including light-emitting diode lasers and organic-based electronic and photonic devices. These technologies suffer from limited lifetimes due to the inevitable degradation of organic semiconductors through poorly defined chemical, photochemical and photophysical processes, especially in operando, or under conditions of operation. Addressing these limitations requires characterization of the molecular structural, electronic, and charge transport attributes of these organic semiconductor materials during and after degradation. Toward this end, a suite of state-of-the-art methods, including surface vibrational spectroscopies (Raman, PM-IRRAS) in ambient to ultrahigh vacuum, x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), inverse photoemission spectroscopy (IPES), and charge mobility measurements, are used to study organic semiconductors in environments that systematically increase in chemical and optoelectronic complexity, including in operando. The primary objective of this effort is to undertake a comprehensive fundamental investigation of the chemical, photochemical, and photophysical mechanisms of degradation that underlie the diminished performance and eventual failure of organic semiconductor-based devices. The secondary impact of this effort is formulation of new design criteria for more robust organic semiconductors.
