Description
Date/Time: 04-23-2019 - Tuesday - 05:00 PM - 07:00 PM
Cathy Wong1

1, University of Oregon, Eugene, Oregon, United States

In situ diagnostics can yield fundamental insights into the materials formation process and aid in the design and optimization of materials for energy technologies, but in situ measurement has not been widely adopted for many time-resolved spectroscopic measurements. In particular, transient absorption (TA) spectroscopy can reveal the kinetic pathways of photoexcited species that dictate materials function, but TA is rarely performed in situ during materials formation. In TA a pump pulse photogenerates electronic excitations in the material, and the differential absorption caused by these excited species is measured by a probe pulse after a controlled delay time. The measurements at each delay time are typically collected in series, resulting in data acquisition times from many minutes to multiple hours. Many materials undergo formation processes on a shorter timescale than the data acquisition time for TA, precluding the accurate measurement of excited state dynamics in these systems. In this work, we introduce a novel implementation of transient absorption spectroscopy that can measure transients with up to a 60 ps pump-probe time delay in one shot. Data with an excellent signal-to-noise ratio can be acquired in just a few seconds. The measurement is validated by comparison to typical implementations of TA in static systems, and we report the results of in situ measurements during the formation of materials with applications in photovoltaics and light emitting devices. The information gained using this technique will be used to modify environmental parameters during the materials formation process to steer the material towards kinetically trapped states with excited state dynamics tailored for particular types of devices.

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