Bodunov E N, Antonov Yu A, Simões Gamboa A L
Department of Physics, Emperor Alexander I St. Petersburg State Transport University, 190031 St. Petersburg, Russia.
International Research and Education Centre for Physics of Nanostructures, ITMO University, 197101 St. Petersburg, Russia.
J Chem Phys. 2017 Mar 21;146(11):114102. doi: 10.1063/1.4978396.
The non-exponential room temperature luminescence decay of colloidal quantum dots is often well described by a stretched exponential function. However, the physical meaning of the parameters of the function is not clear in the majority of cases reported in the literature. In this work, the room temperature stretched exponential luminescence decay of colloidal quantum dots is investigated theoretically in an attempt to identify the underlying physical mechanisms associated with the parameters of the function. Three classes of non-radiative transition processes between the excited and ground states of colloidal quantum dots are discussed: long-range resonance energy transfer, multiphonon relaxation, and contact quenching without diffusion. It is shown that multiphonon relaxation cannot explain a stretched exponential functional form of the luminescence decay while such dynamics of relaxation can be understood in terms of long-range resonance energy transfer to acceptors (molecules, quantum dots, or anharmonic molecular vibrations) in the environment of the quantum dots acting as energy-donors or by contact quenching by acceptors (surface traps or molecules) distributed statistically on the surface of the quantum dots. These non-radiative transition processes are assigned to different ranges of the stretching parameter β.
胶体量子点的非指数室温发光衰减通常能用拉伸指数函数很好地描述。然而，在文献报道的大多数情况下，该函数参数的物理意义并不明确。在这项工作中，对胶体量子点的室温拉伸指数发光衰减进行了理论研究，试图确定与该函数参数相关的潜在物理机制。讨论了胶体量子点激发态与基态之间的三类非辐射跃迁过程：长程共振能量转移、多声子弛豫以及无扩散的接触猝灭。结果表明，多声子弛豫无法解释发光衰减的拉伸指数函数形式，而这种弛豫动力学可以通过长程共振能量转移到量子点环境中作为能量供体的受体（分子、量子点或非谐分子振动），或者通过量子点表面统计分布的受体（表面陷阱或分子）的接触猝灭来理解。这些非辐射跃迁过程被分配到拉伸参数β的不同范围。
