Singlet Exciton Diffusion in Conjugated Polymers: Relaxation and Thermal Activation

单重态激子是有机半导体中主要的光激发态，其扩散分别在有机发光二极管和光致发光器件的性能中起着核心作用。使用共焦光致发光光谱，我们的目标是了解激子寿命和激子扩散系数的热激活在一系列不同的系统相关的太阳能电池的空间分辨率在亚微米范围内。特别是，我们要研究：·共轭聚合物PCDTBT中的同偶缺陷和分子量的影响，重点是热活化·通过溶剂蒸气退火控制P3 HT中球晶生长，不同尺寸的区域及其边界内激子扩散的不同特征·通过比较本体异质结膜中聚合物-富勒烯与聚合物-非富勒烯的能量差异的影响，有机太阳能电池中的新型非富勒烯受体如何影响激子扩散和相关的功率转换效率·有效的Förster-这种系统的半径可以通过实验和模拟的组合来确定。我们将通过低，将不同量的光致发光猝灭剂混合到感兴趣的材料中作为起始点。由于这种方法可能有一个不希望的影响球晶生长过程中的溶剂蒸气退火，我们也将建立激子扩散的测定单重态-单重态湮灭共聚焦荧光显微镜，这不需要淬灭剂。动力学蒙特卡罗模拟的支持下，我们结合的方法使我们能够确定本地激子寿命和亚微米尺度上的扩散系数。

The diffusion of singlet excitons, the primary photoexcited species in organic semiconductors, plays a central role in the performance of organic light emitting diodes and photovoltaics, respectively. Using confocal photoluminescence spectroscopy, our goal is to understand the thermal activation of exciton lifetime and exciton diffusion coefficients in a range of different systems relevant for solar cells with spatial resolution in the sub-micrometer range. In particular, we want to study:• the influence of homocoupling defects and molecular weight in the conjugated polymer PCDTBT with focus on thermal activation• the different characteristics of exciton diffusion within different sized domains and their boundaries by controlling the spherulite growth in P3HT with solvent vapour annealing• how novel non-fullerene acceptors in organic solar cells affect exciton diffusion and the related power conversion efficiency by comparing the impact of energetic differences of polymer–fullerene to polymer–non-fullerene in bulk heterojunction films• how the effective Förster-radius for such systems can be determined by a combination of experiments and simulationsWe will employ the bulk quenching technique by a low, varying amount of photoluminescence quencher blended into the materials of interest as starting point. As this method might have an undesired influence on spherulite growth during solvent vapour annealing, we will also establish the determination of exciton diffusion by singlet–singlet annihilation by confocal fluorescence microscopy, which does not require quenchers. Supported by kinetic Monte Carlo simulations, our combined approach allows us to determine local exciton lifetimes and diffusion coefficients on the sub-micron scale.