Institute of Physics, University of Brasília, Brasília, 70910-900, Brasília, Brazil.
Phys Chem Chem Phys. 2019 Jan 23;21(4):1711-1716. doi: 10.1039/c8cp05951a.
Excitons play a critical role in light emission when it comes to organic semiconductors. In high exciton concentration regimes, monomolecular and bimolecular routes for exciton recombination can yield different products affecting significantly the material's optical properties. Here, the dynamical decay of excitons is theoretically investigated using a kinetic Monte Carlo approach that addresses singlet exciton diffusion. Our numerical protocol includes two distinct exciton-exciton interaction channels: exciton annihilation and biexciton cascade emission. Our findings reveal that these channels produce different consequences concerning diffusion and spectroscopic properties, being able to explain diverging experimental observations. Importantly, we estimate critical exciton densities for which bimolecular recombination becomes dominant and investigate its effect on average exciton lifetimes and diffusion lengths.
激子在有机半导体的发光中起着至关重要的作用。在高激子浓度的情况下，激子复合的单分子和双分子途径可以产生不同的产物，显著影响材料的光学性质。在这里，我们使用一种动力学蒙特卡罗方法来理论研究激子的动态衰减，该方法解决了单重态激子的扩散问题。我们的数值方案包括两个不同的激子-激子相互作用通道：激子湮没和双激子级联发射。我们的研究结果表明，这些通道在扩散和光谱性质方面产生了不同的结果，能够解释实验观察到的差异。重要的是，我们估计了双分子复合变得占主导地位的激子临界密度，并研究了其对平均激子寿命和扩散长度的影响。
