Department of Physics, Chemistry, and Biology, Linköping University, Linköping, Sweden.
J Chem Phys. 2013 Apr 28;138(16):164905. doi: 10.1063/1.4802764.
Exciton dissociation in a donor-accepter polymer heterojunction has been simulated using a nonadiabatic molecular dynamics approach, which allows for the coupled evolution of the nuclear degrees of freedom and the electronic degrees of freedom described by multiconfigurational electronic wavefunctions. The simulations reveal important details of the charge separation process: the exciton in the donor polymer first dissociates into a "hot" charge transfer state, which is best described as a polaron pair. The polaron pair can be separated into free polaron charge carriers if a sufficiently strong external electric field is applied. We have also studied the effects of inter-chain interaction, temperature, and the external electric field strength. Increasing inter-chain interactions makes it easier for the exciton to dissociate into a polaron pair state, but more difficult for the polaron pair to dissociate into free charge carriers. Higher temperature and higher electric field strength both favor exciton dissociation as well as the formation of free charge carriers.
利用非绝热分子动力学方法模拟了给体-受体聚合物异质结中的激子解离，该方法允许通过多组态电子波函数描述的核自由度和电子自由度的耦合演化。模拟揭示了电荷分离过程的重要细节：供体聚合物中的激子首先解离成“热”电荷转移态，最好将其描述为极化子对。如果施加足够强的外电场，极化子对可以分离成自由极化子电荷载流子。我们还研究了链间相互作用、温度和外电场强度的影响。增加链间相互作用使激子更容易解离成极化子对态，但使极化子对更难解离成自由电荷载流子。较高的温度和较高的电场强度都有利于激子解离以及自由电荷载流子的形成。
