Presentation Title

Low-Frequency Dynamics in Organic Semiconductors and Their Effects Upon Semiconducting Efficiency

Abstract

Organic semiconductors have been of considerable interest for their applications in flexible, large-area, and transparent devices. The small molecules and polymers used in these materials are readily synthesized in solution with high synthetic yields, resulting in an energy-efficient manner in which optoelectronics are fabricated. One critical benchmark in the evaluation of semiconductors is the charge-carrier mobility, or the efficiency of moving a charged particle throughout the medium. Mono-crystalline silicon, a prominent semiconductor, displays very high experimental mobility values, but requires a vastly energy-intensive manufacturing process, and cannot be employed in flexible or transparent devices as organic semiconductors can. Major concerns facing organic semiconductors are largely dominated by low charge carrier mobility values, as well as values that vary significantly from one material to another. Low-frequency vibrations in crystalline materials, or phonons, have been shown to strongly localize charge carriers, diminishing semiconducting behavior through a phenomenon called electron-phonon coupling. Terahertz time-domain spectroscopy is a powerful method in the evaluation of organic semiconductors, as the detrimental phonons are directly probed. When coupled with highly-accurate solid-state density functional theory, the specific motions of low-frequency vibrations are unveiled, revealing crucial information regarding structural components of the small molecules that can be exploited to improve charge-carrier mobilities of future derivatives.

Primary Faculty Mentor Name

Michael Ruggiero

Status

Graduate

Student College

Graduate College

Program/Major

Chemistry

Primary Research Category

Engineering & Physical Sciences

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Low-Frequency Dynamics in Organic Semiconductors and Their Effects Upon Semiconducting Efficiency

Organic semiconductors have been of considerable interest for their applications in flexible, large-area, and transparent devices. The small molecules and polymers used in these materials are readily synthesized in solution with high synthetic yields, resulting in an energy-efficient manner in which optoelectronics are fabricated. One critical benchmark in the evaluation of semiconductors is the charge-carrier mobility, or the efficiency of moving a charged particle throughout the medium. Mono-crystalline silicon, a prominent semiconductor, displays very high experimental mobility values, but requires a vastly energy-intensive manufacturing process, and cannot be employed in flexible or transparent devices as organic semiconductors can. Major concerns facing organic semiconductors are largely dominated by low charge carrier mobility values, as well as values that vary significantly from one material to another. Low-frequency vibrations in crystalline materials, or phonons, have been shown to strongly localize charge carriers, diminishing semiconducting behavior through a phenomenon called electron-phonon coupling. Terahertz time-domain spectroscopy is a powerful method in the evaluation of organic semiconductors, as the detrimental phonons are directly probed. When coupled with highly-accurate solid-state density functional theory, the specific motions of low-frequency vibrations are unveiled, revealing crucial information regarding structural components of the small molecules that can be exploited to improve charge-carrier mobilities of future derivatives.