Figure 2. Carrier density dynamics of perovskites.

(a) TA kinetics of MAPbI₃ after 650 nm 100 fs pulsed excitation. Time zero for different fluences was shifted to overlay absolute values with the respective next higher fluence. We find that the transient decays match very well and conclude that the recombination rate dn/dt is only dependent on carrier density n(t). (b–d) Recombination rate dn/dt over charge density n for (b) MAPbI₃, (c) MAPbBr₃ and (d) MAPbI_3−xCl_x. The values were extracted from TA measurements for ∼10 different fluences with each symbol representing one measurement. The normalized TA kinetics were multiplied with the initial charge carrier density n₀ (determined from fluence and absorption values, see Supplementary Note 1) and taking the time-derivative of this carrier density n(t). We observe different scalings of the recombination rate dn/dt with n indicating transitions between different recombination mechanisms. The solid lines are a guidance to the eye.