Balzer Daniel, Kassal Ivan
School of Chemistry, University of Sydney, Sydney, New South Wales 2006, Australia.
J Phys Chem Lett. 2023 Mar 2;14(8):2155-2162. doi: 10.1021/acs.jpclett.2c03886. Epub 2023 Feb 20.
Large exciton diffusion lengths generally improve the performance of organic semiconductor devices, because they enable energy to be transported farther during the exciton lifetime. However, the physics of exciton motion in disordered organic materials is not fully understood, and modeling the transport of quantum-mechanically delocalized excitons in disordered organic semiconductors is a computational challenge. Here, we describe delocalized kinetic Monte Carlo (dKMC), the first model of three-dimensional exciton transport in organic semiconductors that includes delocalization, disorder, and polaron formation. We find that delocalization can dramatically increase exciton transport; for example, delocalization across less than two molecules in each direction can increase the exciton diffusion coefficient by over an order of magnitude. The mechanism for the enhancement is 2-fold: delocalization enables excitons to hop both more frequently and further in each hop. We also quantify the effect of transient delocalization (short-lived periods where excitons become highly delocalized) and show that it depends strongly upon the disorder and transition dipole moments.
大的激子扩散长度通常会提高有机半导体器件的性能，因为它们能使能量在激子寿命期间传输得更远。然而，无序有机材料中激子运动的物理机制尚未完全理解，并且对无序有机半导体中量子力学离域激子的传输进行建模是一项计算挑战。在此，我们描述了离域动力学蒙特卡罗（dKMC）方法，这是有机半导体中三维激子传输的首个模型，该模型包含离域、无序和极化子形成。我们发现离域能显著增加激子传输；例如，在每个方向上跨越不到两个分子的离域就能使激子扩散系数增加一个数量级以上。增强的机制有两方面：离域使激子在每次跳跃中更频繁且跳跃得更远。我们还量化了瞬态离域（激子高度离域的短暂时期）的影响，并表明其强烈依赖于无序和跃迁偶极矩。
