Center for Nano and Molecular Science and Technology, University of Texas, Austin, TX 78712, USA.
Science. 2011 Feb 4;331(6017):565-7. doi: 10.1126/science.1199140.
In conjugated polymers, radiative recombination of excitons (electron-hole pairs) competes with nonradiative thermal relaxation pathways. We visualized exciton quenching induced by hole polarons in single-polymer chains in a device geometry. The distance-scale for quenching was measured by means of a new subdiffraction, single-molecule technique--bias-modulated intensity centroid spectroscopy--which allowed the extraction of a mean centroid shift of 14 nanometers for highly ordered, single-polymer nanodomains. This shift requires energy transfer over distances an order of magnitude greater than previously reported for bulk conjugated polymers and far greater than predicted by the standard mechanism for exciton quenching, the unbiased diffusion of free excitons to quenching sites. Instead, multistep "energy funneling" to trapped, localized polarons is the probable mechanism for polaron-induced exciton quenching.
在共轭聚合物中，激子（电子-空穴对）的辐射复合与非辐射热弛豫途径竞争。我们在器件结构中可视化了单聚合物链中空穴极化子诱导的激子猝灭。猝灭的距离尺度通过一种新的亚衍射、单分子技术——偏压调制强度质心光谱学来测量，该技术允许提取高度有序的单聚合物纳米域的平均质心位移为 14 纳米。与之前报道的体共轭聚合物相比，这种位移需要在距离上传递能量，其数量级要大得多，远远超过激子猝灭标准机制——自由激子无偏扩散到猝灭位点的预测。相反，多步“能量漏斗”到被捕获的局部极化子可能是极化子诱导激子猝灭的机制。
