Abnormal Temperature Dependence of Huang-Rhys Factor and Exciton Recombination Kinetics in CsPbBr 3 Perovskite Quantum Dots

Anomalous thermal behaviors of excitonic luminescence in CsPbBr perovskite quantum dots (PQDs) were observed. It is found that the main luminescence peak originated from the excitonic radiative recombination assisted by the longitudinal-optical (LO) phonon, and its integrated intensity first declines as the temperature varies from 10 to 150 K and then turns to increase at ∼160 K, reaching a maximum value at 300 K. A model considering the thermal detrapping and transfer of electrons from a trap level is developed to interpret these abnormal thermal behaviors of the luminescence from the PQDs. On the other hand, the quantum-mechanical multimode Brownian oscillator model was employed to unravel that the Huang-Rhys factor exclusively characterizing the exciton-phonon coupling in the studied CsPbBr PQDs decreases from 1.65 at 10 K to 1.31 at 200 K.