Molecules, polymers, and nanocrystals can form the active layer in electronic devices such as photovoltaics and light-emitting diodes. Their electronic structure and excited state dynamics dictate their function and suitability for these applications. Transient absorption (TA) spectroscopy is used to measure these properties, and has provided remarkable insights into the behavior and function of electronic materials. However, multiple minutes-to-hours are typically required to perform these measurements, making it difficult to accurately measure the excited state dynamics of unstable and evolving materials systems such as electronic materials during their synthesis or deposition into a thin film. In this seminar, a novel implementation of TA spectroscopy is introduced that can measure transient spectra in 8 ms, with good signal-to-noise achieved in ~30 s. Instrument design strategies that are unique to this TA acquisition method are discussed, such as the use of a spatial light modulator to ensure even excitation intensity and the use of a double-chopping scheme to dynamically subtract evolving background signals. Examples of this new technique applied to the study of materials formation demonstrate that in addition to providing an understanding of how excited state dynamics change during materials formation, TA signals measured in situ can reveal new insights into the mechanisms of complex materials formation processes.

Probing materials formation using in situ transient absorption spectroscopy

ACS Fall 2021

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