Exciton, Biexciton, and Hot Exciton Dynamics in CsPbBr3 Colloidal Nanoplatelets

Lead halide perovskites have emerged as promising materials for light-emitting devices. Here, we report the preparation of colloidal CsPbBr3 nanoplatelets (3 x 4 x 23 nm(3)) experiencing a strong quasi-one-dimensional quantum confinement. Ultrafast transient absorption and broadband fluorescence up-conversion spectroscopies were employed to scrutinize the carrier and quasiparticle dynamics and to obtain a full description of the spectroscopic properties of the material. An exciton binding energy of 350 meV, an absorption cross section at 3.2 eV of 5.0 +/- 0.3 x 10(-15) cm(-2), an efficient biexciton Auger recombination lifetime of 9 +/- 1 ps, and a biexciton binding energy of 74 +/- 4 meV were determined. Moreover, a short-lived emission from hot excitons was observed, which is related to the formation of band-edge excitons. The time constant of both processes is 300 +/- 50 fs. These results show that CsPbBr3 nanoplatelets are indeed quite promising for light-emitting technological applications.