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Resolving ultrafast exciton migration in organic solids at the nanoscale
Nature Materials ( IF 41.2 ) Pub Date : 2017-09-18 , DOI: 10.1038/nmat4975
Samuel B. Penwell , Lucas D. S. Ginsberg , Rodrigo Noriega , Naomi S. Ginsberg

Effectiveness of molecular-based light harvesting relies on transport of excitons to charge-transfer sites. Measuring exciton migration, however, has been challenging because of the mismatch between nanoscale migration lengths and the diffraction limit. Instead of using bulk substrate quenching methods, here we define quenching boundaries all-optically with sub-diffraction resolution, thus characterizing spatiotemporal exciton migration on its native nanometre and picosecond scales. By transforming stimulated emission depletion microscopy into a time-resolved ultrafast approach, we measure a 16-nm migration length in poly(2,5-di(hexyloxy)cyanoterephthalylidene) conjugated polymer films. Combined with Monte Carlo exciton hopping simulations, we show that migration in these films is essentially diffusive because intrinsic chromophore energetic disorder is comparable to chromophore inhomogeneous broadening. Our approach will enable previously unattainable correlation of local material structure to exciton migration character, applicable not only to photovoltaic or display-destined organic semiconductors but also to explaining the quintessential exciton migration exhibited in photosynthesis.



中文翻译:

解决纳米级有机固体中的超快激子迁移

基于分子的光收集的有效性取决于激子向电荷转移位点的运输。然而,由于纳米级迁移长度和衍射极限之间的不匹配,因此测量激子迁移一直是一项挑战。而不是使用块状衬底淬灭方法,这里我们以亚衍射分辨率全光学定义淬灭边界,从而在其自然的纳米和皮秒尺度上表征时空激子迁移。通过将受激发射耗竭显微镜转换为时间分辨的超快方法,我们测量了聚(2,5-二(己氧基)氰基对苯二甲叉基)共轭聚合物薄膜中的16 nm迁移长度。结合蒙特卡洛激子跳跃仿真,我们表明,在这些薄膜中的迁移本质上是扩散性的,因为内在的生色团高能紊乱可与生色团的不均匀扩宽相媲美。我们的方法将使以前无法实现的局部材料结构与激子迁移特性相关,不仅适用于光伏或以显示器为目标的有机半导体,而且还可用于解释光合作用中表现出的典型激子迁移。

更新日期:2017-09-21
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