Dynamics of photoexcited charge carriers in self-organized organic bulk semiconductors

整个项目的目标是发展分子顺序对过程动力学的影响的基本理解，发生在具有可变结构的分子体半导体中，沿着整个过程链，从光吸收到载流子传输。对于有机体半导体来说，局部迁移率和宏观迁移率都很重要。前者反映了材料本身的潜力，后者是器件应用的基本参数。理想情况下，人们需要了解整个情况，才能认识到任何新开发材料的应用潜力，并对其优化提供反馈：要么是材料本身（在低局部迁移率的情况下），要么是被测设备（宏观迁移率远低于局部迁移率）。在下一个项目阶段，我们将应用瞬态微波导电性（TRMC）的方法来研究由for1809合作伙伴提供的材料、聚合物和低聚物的微观输运性质。TRMC是基于这样一个事实，即由光脉冲产生的电荷载流子会导致所研究的材料中的介电损耗（微波吸收）。然而，只有在载流子密度已知的情况下，才能对TRMC测量进行定量分析。因此，在理想情况下，微波响应的测量应该与光密度的测量一起进行，例如在相同的条件下通过瞬态吸收（TA）。在第一个资助期，我们成功地构建了一个组合装置，它允许在相同的激光激发脉冲下同时对同一样品进行TRMC和TA，同时甚至包括一个低温恒温器用于温度相关的测量。我们将利用这种方法系统地研究基于方碱偶联物的大分子。与此相反，吲哚胺-方胺可以以拉伸之字形或螺旋状聚合物结构的形式产生。因此，研究上层结构对局部载流子输运的影响是很有意义的。此外，我们计划对层次化过二酰亚胺衍生物进行TA/TRMC研究，形成Jaggregates，这些Jaggregates在整体上是液晶的，但也可能在液体溶液中形成聚集体。同样，发现聚集态对局部电荷动力学和输运性质的影响将是有趣的。为了解决光伏器件的宏观电导率特性，我们将进行瞬态电导率测量，如OTRACE， TDCF, ToF, TPV/TPC。理论分析将与研究小组内的理论伙伴合作完成。

The overall project goal is to develop a fundamental understanding of the influence of molecular order on the dynamics of the processes, occurring in molecular bulk semiconductors with variable architecture, along the whole process chain, from light absorption to charge carrier transport. For organic bulk semiconductors, both local and macroscopic mobilities are of importance. The former reflects the potential of the material itself, the second is the essential parameter for device applications. Ideally, one needs to know the whole picture to recognize the application potential of any newly developed material and to deliver feedback on its optimisation: either of the material itself (in case of low local mobility) or of the device under test (macroscopic mobility by far lower than local mobility). In the next project phase, we will apply the method of transient microwave conductivity (TRMC) for selected materials, polymers and oligomers, provided by the FOR 1809 partners, to investigate their microscopic transport properties. TRMC is based on the fact that charge carriers, generated by a light pulse, lead to dielectric losses in the material under study (microwave absorption). A quantitative analysis of TRMC measurements, however, is only possible, if the charge carrier density is known. Therefore, measurement of the microwave response should ideally be done together with measurements of optical density via, e.g. transient absorption (TA) under the same conditions. In the first funding period we succeeded in the construction of a combined set-up, which allows, to carry out both TRMC and TA simultaneously, on the same sample during the same laser excitation pulse, while even including a cryostat for temperature-dependent measurements. We will use this method to systematically study macromolecules based on squaraine conjugates. In contrast to that, indolenine-squaraines can be produced specifically in the form of stretched zig-zag or helical polymer structures. Therefore it is interesting to investigate the influence of the superstructure on the local charge carrier transport. Further, we plan to perform TA/TRMC studies on hierarchical perylenbisimide derivates, forming Jaggregates, which are liquid crystalline in bulk, but may also form aggregates in liquid solution. Again, it will be interesting to find the influence of the aggregate state on local charge dynamics and transport properties. To address the macroscopic conductivity properties of photovoltaic devices, we will perform transient conductivity measurements, such as OTRACE, TDCF, ToF, TPV/TPC. Theoretical analysis will be done in collaboration with the theory partners within the research group.