Direct probe of spectrally narrowed emission from π-conjugated polymers: The elucidation of mechanism for spectral line narrowing
Direct probe of spectrally narrowed emission from π-conjugated polymers: The elucidation of mechanism for spectral line narrowing
复制标题
直接探测π共轭聚合物的光谱变窄发射：阐明光谱线变窄的机制
DOI：
--
复制
发表时间：
2002
期刊：
影响因子：
--
通讯作者：
Dongho. Kim
中科院分区：
文献类型：
--
作者：
S. Jeoung;D. Jeong;T. Ahn;Ja;Min;H. Shim;Dongho. Kim
π共轭聚合物薄膜的飞秒时间分辨发射和瞬时吸收光谱表明，与正常发射的瞬时增强相比，光谱窄化发射的出现有明显的诱导时间。这些与强度相关的超快光谱研究表明，π共轭聚合物中单重态激发态现象的起源是放大的自发辐射，它能迅速而有效地引起单态激子的退居。此外，对SNE、正常辐射和受激辐射的时间分布的比较表明，引起SNE过程的光激发是单重态激子。通过改变激发功率密度、光斑大小和聚合物的平均π共轭长度测量的近场效应的时间分布表明，建立时间对产生强的近场效应起着重要作用。这些发现表明，泵浦几何形状、样品形态、缺陷位置以及结晶度都是很重要的。
Femtosecond time-resolved emission as well as transient absorption spectroscopy of π-conjugated polymeric thin film revealed an apparent induction time for the appearance of spectrally narrowed emission (SNE) in contrast with an instantaneous buildup of normal emission. These ultrafast intensity-dependent spectroscopic studies demonstrate that the origin of SNE phenomena in π-conjugated polymer is amplified spontaneous emission (ASE), which induces prompt and efficient depopulation of singlet excitons. Furthermore, comparison of temporal profiles of SNE, normal emission and stimulated emission reveals that the photoexcitations responsible for SNE processes are singlet excitons. The temporal profiles of SNE measured by changing excitation power density, illuminated spot size, and average π-conjugation length of polymer show that a build-up time plays an important role in generating intense SNE. These findings imply that pumping geometry, sample morphology, defect sites, as well as crystallinity are strongl...