Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany.
Phys Rev Lett. 2014 Apr 4;112(13):137402. doi: 10.1103/PhysRevLett.112.137402. Epub 2014 Apr 2.
Control of chain length and morphology in combination with single-molecule spectroscopy techniques provides a comprehensive photophysical picture of excited-state losses in the prototypical conjugated polymer poly(3-hexylthiophene) (P3HT). Our examination reveals a universal self-quenching mechanism, based on singlet-triplet exciton annihilation, which accounts for the dramatic loss in fluorescence quantum yield of a single P3HT chain between its solution (unfolded) and bulklike (folded) state. Triplet excitons fundamentally limit the fluorescence of organic photovoltaic materials, which impacts the conversion of singlet excitons to separated charge carriers, decreasing the efficiency of energy harvested at high excitation densities. Interexcitonic interactions are so effective that a single P3HT chain of order 100 kDa weight behaves like a 2-level system, exhibiting perfect photon antibunching.
控制链长和形态，结合单分子光谱技术，为典型共轭聚合物聚（3-己基噻吩）（P3HT）的激发态损耗提供了全面的光物理图像。我们的研究揭示了一种普遍的自猝灭机制，基于单重态-三重态激子湮灭，这解释了在其溶液（展开）和类似体相（折叠）状态之间，单个 P3HT 链的荧光量子产率的急剧损失。三重态激子从根本上限制了有机光伏材料的荧光，这影响了单重态激子向分离电荷载流子的转化，降低了在高激发密度下能量的收集效率。激子间相互作用非常有效，以至于一个 100 kDa 量级的单个 P3HT 链表现得像一个 2 能级系统，表现出完美的光子反聚束。
