(a) Maxima in the pulse-radiolysis time-resolved microwave conductance (PRTRMC) traces at different temperatures. Reproduced with permission from Bartesaghi et al., J. Phys. Chem. C 122, 4809 (2018). Copyright 2018 Author(s), licensed under a Creative Commons Attribution (CC BY-NC-ND) license. (b) PL linewidth of Cs₂AgBiBr₆ SC as a function of the temperature. Solid and dashed lines correspond to fitting with the conventional model for weak coupling and strong coupling, respectively. Reproduced with permission from Wu et al., Sci. Adv. 7, eabd3160 (2021). Copyright 2021 Author(s), licensed under a Creative Commons Attribution (CC BY-NC) license. (c) Optical pump terahertz probe (OPTP) photoconductivity transients for a Cs₂AgBiBr₆ thin film, measured at different temperatures under an excitation fluence of 10.1 μJ cm⁻². The transients at successively decreasing temperatures are offset vertically to aid visualization. The two-level charge-carrier mobility model was used to fit the data as represented by gray lines. (d) Temperature dependence of the effective charge-carrier mobilities associated with the delocalized (μ_deloc, green) and localized (μ_loc, blue) states in Cs₂AgBiBr₆ based on the OPTP measurements shown in part (c). The solid lines represent the relative change in ϕμ with respect to relative change in temperature in the corresponding colors with their exponents (p) displayed alongside. The data points for μ_deloc at the lowest two temperatures were not included in the plot, since the relative change is very small in that region indicated by the dashed green line. The mobilities are “effective” since the photon-to-charge branching ratio, ϕ, is not necessarily 1. Both parts (c) and (d) are reproduced with permission from Wright et al., J. Phys. Chem. Lett. 12, 3352 (2021). Copyright 2021 American Chemical Society. (e) Illustration of the proposed mechanism for self-trapping and luminescence from Cs₂AgBiBr₆ based on the discussion made in J. Phys. Chem. Lett. 12, 3352 (2021)¹⁷ and Sci. Adv. 7, eabd3160 (2021).¹⁸ (f) Kinetic decay in the transient absorption spectra of BiI₃ on mesoporous TiO₂, measured at 665 nm wavelength. The excitation wavelength was 400 nm. A Fourier transform was made on the oscillatory component of the kinetic decay curve, and this is shown in the bottom plot. Both plots are reproduced with permission from Scholz et al., Phys. Chem. Chem. Phys. 20, 10677 (2018). Copyright 2018 Royal Society of Chemistry.