Abnormal Temperature Dependence of Huang–Rhys Factor and Exciton Recombination Kinetics in CsPbBr₃ Perovskite Quantum Dots

Anomalous thermal behaviors of excitonic luminescence in CsPbBr₃ 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 CsPbBr₃ PQDs decreases from 1.65 at 10 K to 1.31 at 200 K.