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

该项目的总体目标是对分子有序对过程动力学的影响有一个基本的了解，这些过程发生在具有不同结构的分子体半导体中，沿着整个过程链，从光吸收到电荷载流子传输。对于有机块体半导体来说，局域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，人们需要了解整体情况，才能认识到任何新开发的材料的应用潜力，并就其优化提供反馈：要么是材料本身(如果局部迁移率低)，要么是被测试设备的(宏观迁移率远远低于局部迁移率)。在下一个项目阶段，我们将应用For 1809合作伙伴提供的选定材料、聚合物和低聚物的瞬时微波电导率(TRMC)方法来研究它们的微观传输特性。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被研究材料的介电损耗(微波吸收)。然而，只有在电荷载流子密度已知的情况下，才有可能对TRMC测量进行定量分析。因此，理想情况下，微波响应的测量应与光学密度的测量一起进行，例如在相同条件下的瞬时吸收(TA)。在第一个资助期，我们成功地建立了一个组合装置，它允许在同一激光激发脉冲期间对同一样品同时进行TRMC和TA，同时甚至包括一个用于温度相关测量的低温恒温器。我们将利用这种方法系统地研究基于方酸共轭化合物的大分子。相反，吲哚方块可以以拉伸的Z字形或螺旋聚合物结构的形式产生。因此，研究超结构对局域载流子输运的影响是很有意义的。此外，我们计划对分级的perenbisimide衍生物进行TA/TRMC研究，形成J聚集体，这些聚集体在整体上是液晶的，但也可能在液体中形成聚集体。同样，发现聚集态对局域电荷动力学和输运性质的影响将是有趣的。为了研究光伏器件的宏观电导特性，我们将进行瞬时电导测量，如OTRACE、TDCF、ToF、TPV/TPC。理论分析将与研究组内的理论合作伙伴合作进行。

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.