Understanding perovskite nanocrystal growth using in situ transient absorption spectroscopy

Transient absorption spectroscopy can measure exciton dynamics and provide insight into the electronic structure of nanocrystals (NCs). This spectroscopy, however, is typically limited by the long timescales required for acquisition of transient spectra, preventing the accurate measurement of systems that are not at a structural equilibrium. The structure of NCs changes during their synthesis on a shorter timescale than that required for measurement, making it difficult to study the evolving photophysics of NCs during growth. Here, we leverage a single-shot transient absorption (SSTA) spectrometer, capable of recording transient spectra with excellent signal-to-noise in less than a minute, to measure exciton dynamics in growing NCs. The presence of internal electric fields caused by surface-trapped carriers is evident in the TA lineshape, where a distinct Stark effect is observed revealing that growing NCs are poorly passivated. This work will enable a range of future experiments to study charge carrier behavior in rapidly evolving NC systems.