Charge carrier mobility and diffusion in conjugated polymers

近年来，人们在研究有机无序半导体如共轭聚合物中的电荷输运方面取得了很大的进展，特别是考虑到载流子的迁移率。然而，电荷载流子扩散系数在很大程度上被忽略了-这是因为通常情况下，爱因斯坦关系式D/µ=KT/Q被隐含地假设为有效。到目前为止，有机无序半导体的载流子迁移率µ和扩散系数D以及它们与温度的关系还没有报道过，只有一个例外，爱因斯坦关系被发现是无效的。关于直接测定D和µ的系统方法，也考虑到温度相关性，缺乏系统的方法。这是尽管爱因斯坦关系对器件性能有明显影响的事实，因为二极管特性和非对称复合动力学-与扩散系数成正比，而不是载流子迁移率-受偏离其通常形式的影响。在这个方案中，我们将尝试研究有机半导体中的载流子扩散系数和迁移率，以实验确定爱因斯坦关系式的推广形式，D/µ=Χ·kt/q。为了更基本的理解，我们将用跳跃主方程的计算和宏观模拟来补充这些实验。对于后者，还将评估广义爱因斯坦关系对有机电子器件性能的影响。因此，目标将是直接确定爱因斯坦关系及其对有机电子设备性能的影响，这是指导优化的要求，也是通向基本理解的重要一步。

A significant progress has been made in recent years for the understanding of charge transport in organic disordered semiconductors such as conjugated polymers, particularly in view of the charge carrier mobility. The charge carrier diffusion coefficient, however, has been mostly neglected—the reason being that usually the Einstein relation D/µ = kT/q was implicitly assumed to be valid. Up to now, charge carrier mobility µ and diffusion coefficient D and their temperature dependence have not been reported together for organic disordered semiconductors, with one exception, where the Einstein relation was found not to be valid. A systematic approach concerning the direct determination of D and µ, also accounting for the temperature dependence, is lacking. This is despite the fact that the Einstein relation has a clear impact on the device performance, as diode characteristics and nongeminate recombination dynamics—which are proportional to the diffusion coefficient, not the charge carrier mobility—are influenced by deviations from its usual form. Within this proposal, we will attempt to investigate the charge carrier diffusion coefficient and the mobility in organic semiconductors, in order to experimentally determine the generalized form of the Einstein relation, D/µ = Χ • kT/q. For a more fundamental understanding, we will complement these experiments with calculations of the hopping master equation as well as by macroscopic simulations. With the latter, also the influence of a generalised Einstein relation on the device performance of organic electronics will be evaluated. The goal will therefore be to directly determine the Einstein relation and its impact on the performance of organic electronic devices, which is a requirement for a guided optimisation, and an important step to a fundamental understanding.