Fig. 3: Charge-carrier kinetics in NaBiS₂ NC films.

a Long-time transient absorption (TA) spectrum of NaBiS₂ NC films with 355 nm wavelength pump excitations and shown for pump-probe delays of 20 ns (blue) and 10 μs (red), along with b its normalised ground state bleach (GSB) signal kinetics at different pump fluences: 21 (dark pink), 32 (orange), 42 (green) and 53 (light pink) μJ cm⁻² pulse⁻¹. The GSB kinetics were acquired by averaging the signals from 800 to 860 nm (peak 1, shaded area in a) and normalised to the maximum \(\triangle T/T\) values. c Short-time TA spectrum of NaBiS₂ NC films with 400 nm wavelength pump excitations at pump-probe delays of 1 ps (blue), 10 ps (red) and 100 ps (green), along with d its normalised photo-induced absorption (PIA) signal kinetics at different pump fluences: 6 (dark pink), 12 (orange), 24 (green) and 48 (light pink) μJ cm⁻² pulse⁻¹. The PIA kinetics were acquired by averaging the signals from 920 to 960 nm wavelength (shaded area in c) and normalised to the minimum \(\triangle T/T\) values. The black arrows in (a and c) indicate the corresponding wavelength (886 nm) for the optical bandgap (1.4 eV) of NaBiS₂ (Supplementary Fig. 4). e Normalised \(-\triangle T/T\) kinetics of spin-coated NaBiS₂ NC films from optical-pump-terahertz-probe (OPTP) measurements at different 400 nm wavelength pump fluences: 26 (green), 44 (pink) and 73 (purple) μJ cm⁻² pulse⁻¹. Black dashed line represents the fit to the kinetics measured at the highest fluence based on the two-level mobility model (Supplementary Note 4). f Comparison of the normalised signal kinetics acquired from the short-time TA (red circles) and OPTP measurements (green line), recorded at fluences of 12 and 26 μJ cm⁻² pulse⁻¹, respectively.