Department of Physics, Chemistry, and Biology, Linköping University, SE-58183 Linköping, Sweden.
J Chem Phys. 2012 Jun 28;136(24):244901. doi: 10.1063/1.4729483.
We simulate the interchain polaron recombination process in conjugated polymer systems using a nonadiabatic molecular dynamics method, which allows for the coupled evolution of the nuclear degrees of freedom and multiconfigurational electronic wavefunctions. Within the method, the appropriate spin symmetry of the electronic wavefunction is taken into account, thus allowing us to distinguish between singlet and triplet excited states. It is found that the incident polarons can form an exciton, form a bound interchain polaron pair, or pass each other, depending on the interchain interaction strength and the strength of an external electric field. Most importantly, we found that the formation of singlet excitons is considerably easier than triplet excitons. This shows that in real organic light emitting devices, the electroluminescence quantum efficiency can exceed the statistical limitation value of 25%, in agreement with experiments.
我们使用非绝热分子动力学方法模拟了共轭聚合物体系中的链间极化子复合过程，该方法允许核自由度和多组态电子波函数的耦合演化。在该方法中，考虑了电子波函数的适当自旋对称性，从而能够区分单重态和三重态激发态。结果表明，入射极化子可以形成激子，形成束缚的链间极化子对，或者彼此通过，这取决于链间相互作用强度和外部电场强度。最重要的是，我们发现形成单重态激子比三重态激子容易得多。这表明在实际的有机发光器件中，电致发光量子效率可以超过 25%的统计限制值，与实验结果一致。
