Fig. 2: Hot-electron generation and relaxation in FICO nanocrystals.

a Transient absorption (TA) spectra of FICO nanocrystals (NCs) at different delay times with 400–490 nm in left panel and 500–700 nm in right panel. For better view, the amplitude of TA spectra of −0.05 and 0 ps has been multiplied by four times and the vertical axis in right panel (500–700 nm) has been zoomed in by 10 times (×10). Black dashed line shows modeled spectrum at 0.3 ps with T_e of 4500 K. b TA kinetics of FICO NCs probed at 550 nm (empty circles) and the single-exponential fitting (red line) of the rise and decay process. c Scheme showing carrier distribution after hot-electron generation from Landau damping (left) and after electron thermalization through e–e and e–ph scattering (right). E_photon is the pump photon energy. E_f is the Fermi level. \(B_{\mathrm{g}}^\prime\) is the direct bandgap after band renormalization correction. Red dashed arrows show the induced absorption (IA) process. The gray region shows the undisturbed filled states. The orange and blue regions represent the excited electrons and empty states left, respectively, after Landau damping (left) and thermalization (right).