Fig. 2: Size-dependent exciton lifetime at 4 K.

a, Representative photoluminescence (PL) spectra of single CsPbBr₃ perovskite QDs with different sizes. b, Size-dependent mean exciton photoluminescence band-edge emission at 4 K; vertical and horizontal error bars represent the standard deviation of the QD edge length and exciton energy, respectively. The grey solid line is a sizing curve obtained by using an effective-mass model for intermediate confinement. c, TRPL decay of two single QDs in the weak- to intermediate-confinement regime (QD size of 7 nm; blue dots) and weak confinement regime (QD size of 23 nm; vermillion dots), respectively. The solid grey lines indicate single-exponential decays with inferred time constants (defined as 1/e intensity decrease) of 570 ps and 150 ps, for the 7 nm and 23 nm QD, respectively. d, Size-dependent mean exciton lifetime as a function of the exciton energy, acquired at 4 K (coloured circles); vertical and horizontal error bars represent the standard deviation of lifetime and exciton energy, respectively. The lines show the result of theoretical calculations, performed at 0 K and assuming various values for the Kane energy (E_p) shown as dashed and solid lines as indicated in the legend. More details concerning the theoretical model are reported in Supplementary Information.