Ultrafast\nExciton Dynamics in Thin Films of a Two-Dimensional\nPb-Free CsBi<sub>3</sub>I<sub>10</sub> Perovskite

CsBi<sub>3</sub>I<sub>10</sub> perovskite films were\nsynthesized\nby an antisolvent-assisted spin-coating method. The morphology and\ncrystal structure of the CsBi<sub>3</sub>I<sub>10</sub> perovskite\nfilm were characterized using scanning electron microscopy (SEM),\nX-ray diffraction (XRD), and Raman spectroscopy, confirming its crystallinity\nand purity. Ultraviolet–visible (UV–vis) absorption\nspectra revealed two excitonic peaks peaked at 496 and 626 nm. Femtosecond\ntransient absorption spectroscopy (TAS) was utilized to probe the\nexciton dynamics that reveal three dominant processes attributed to\nhot electron cooling, trapping to trap states, electron–hole\nrecombination, and a possible dissociative pathway or high density\nof defect states coupled with the first excited electronic state or\nconduction band (CB), which lead an overall short-lived photoinduced\ncharge carrier or exciton. A kinetic model was proposed to simulate\nand explain these processes that lead to an overall short exciton\nlifetime.