Local mapping of ultrafast carrier/exciton dynamics with transient absorption microscopy

Abstract

Transient absorption (TA) spectroscopy has drawn great attention for examination of the carrier/exciton dynamics in solar cell[1], valleytronics[2], and photocatalytic[3] materials because of its sensitivity to both dark and luminescent states, high temporal resolution, and broadband probe range. With the continuing development of electronic materials, the necessity to understand the effect of microscopic heterogeneity and morphology of materials on its exciton/carrier dynamics has encouraged the development of microscopic study of TA. TAM technique, combining the conventional TA spectroscopy with the optical microscopy, retrieves the shortcoming on the spatial resolution of the TA spectroscopy and opens a new field for the investigation of morphological and structural dependence of photoinduced dynamics. Here, we visualize the TAM technique, which has ultrashort time resolution (~100 fs) and broadband probe ranges (400–1500 nm) with a spatial resolution of 5 μm, and demonstrate its capability of spatial resolution with the novel optoelectronic material, WS2. By resolving the transient absorption spectra of WS2 flakes in both time and space, thickness-dependent and site-specific photoinduced dynamics is demonstrated. References [1] T. H. Lee, W.-W. Park, S. Y. Park, S. Cho, O.-H. Kwon and J. Y. Kim, Solar RRL 5, 2100326 (2021). [2] H. Zhou, Y. Zhao, W. Tao, Y. Li, Q. Zhou, and H. Zhu, ACS Nano 14, 4618-4625 (2020). [3] F. V. A. Camargo, Y. Ben-Shahar, T. Nagahara, Y. E. Panfil, M. Russo, U. Banin, and G. Cerullo, Nano Lett. 21, 1461-1468 (2021).