Thulium Dopant Modulates Nonadiabatic Coupling and Charge Carrier Dynamics of CsPbI2Br Perovskites

The nonadiabatic effect that directly relates lattice thermal motion coupled with an electronic state is the foundation for understanding semiconductor carrier lifetime, nonradiative recombination rate, and related energy loss mechanisms. Herein, in order to clarify how the Tm dopant modulates carrier dynamics of CsPbI2Br, density functional theory calculations and nonadiabatic molecular dynamics simulations were combined to reveal the doping effects. The results indicate that the Tm dopant enhances the interaction with halogen, induces the localized states below Fermi level, reduces the electron–hole overlap and nonadiabatic coupling, and weakens electron states mixing driven by thermal fluctuations. Meanwhile, Tm-induced localized lattice contraction decreases the coupling between carriers and the low-frequency vibration modes of the Pb–I(Br) framework and then accelerates the dephasing process of electronic states, reducing dephasing time, thereby inhibiting multiphonon-assisted nonradiative recombination. These synergistic regulatory effects significantly delay the decay of charge carriers and elongate the nonradiative recombination lifetime.