In situ transient absorption spectroscopy during materials formation
Cathy Wong, University of Oregon
Lead halide perovskite nanocrystals (NCs) are promising materials for light-emitting applications. These NCs exhibit high photoluminescence quantum yields with emission wavelength tunable throughout the visible region, and can be easily synthesized using low-cost solution-based methods at ambient conditions. In this work, we utilize the behavior of excitons to understand the mechanism by which NCs grow. We report on the evolving excited state properties of MAPbI3 NCs during their nucleation and growth using a newly developed transient absorption spectrometer that can measure the excited state dynamics of NCs in situ, during their synthesis. Transient absorption lineshapes are observed that are unique to young NCs, and analysis of these features show that they originate from the Stark effect caused by surface-trapped carriers. These lineshapes can be used to report on the quality of the NC surface during their synthesis.