Study of phosphorescent organic EL materials on single-molecule level

单分子水平磷光有机EL材料的研究

基本信息

批准号：
16550155
负责人：
VACHA Martin
金额：
$ 2.18万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

项目摘要

Single-molecule spectroscopy has been used to characterize optical properties of phosphorescent iridium complexes. For the most typical complex of Ir(ppy)_3, distributions of single molecule emission intensities show profiles asymmetrical towards higher intensities and photobleaching times depend non-linearly on the single molecule emission intensities. These characteristics can be explained as a result of modified optical properties of the complexes, either due to the inhomogeneous environment or due to partial photoreaction of individual ligands. To clarify this point, an iridium complex with one ligand modified, Irfppy(ppy)_2 has been prepared and studied in the same manner. The results indicate that Irfppy(ppy)_2 which emits light via only the aldehyde-modified ligand shows the same wide distribution of emission intensities and that in the case of Ir(ppy)_3 molecular distortion due to the surrounding matrix causes localization of the excitation on and emission from a single ligand. … More Further, picosecond laser diode and time-correlated single-photon counting have been used to study excited state relaxation of Ir(ppy)_3 on ensemble and single molecule level. While the ensemble sample emission decays with the expected 1.2 μs lifetime, decreasing sample concentration is accompanied by the appearance of a short component of 3 ns next to the long 1.2 μs component. Laser repetition frequency dependence reveals that with increasing pulse separation the relative ratio of the short component increases, pointing to the ground-state absorption as its origin. Further, the short component depends on the second power of the excitation laser intensity while for the long component the intensity dependence is linear. This fact points to two-photon absorption as the probable origin of the short component. This is confirmed by one-photon and two-photon excited single-molecule imaging, where the image excited at 488 nm and detected between 370 and 450 nm is very similar to the usual one-photon excited image. The two-photon absorption is a π-π* ligand-centered transition. After excitation, the energy is transferred via internal conversion to the ^1MLCT state from where the short-lived fluorescence is emitted. Less

单分子光谱已用于表征复合物的光学特性，要么是由于不均匀的环境或由于单个配体的部分光反应。为了澄清这一点，已经制备了带有一个配体修饰的虹膜络合物irfppy（ppy）_2并以相同的方式进行研究。结果表明，仅通过醛修饰的配体发出光的Irfppy（PPY）_2显示出相同的发射强度分布，并且在IR（PPY）_3分子失真的情况下，由于周围的基质引起的基质引起的兴奋，并引起了单个Ligand的兴奋。 …更重要的是，皮秒激光二极管和时间相关的单光子计数已用于研究集合和单分子水平上IR（PPY）_3的激发状态放松。虽然整体样品发射的寿命具有预期的1.2μs寿命，但样品浓度的降低是通过出现在长1.2μs分量旁边的3 ns的短成分来实现的。激光重复频率依赖性表明，随着脉冲分离的增加，短成分的相对比率增加，表明地面损失是其起源。此外，短成分取决于兴奋激光强度的第二功率，而对于长组件，强度依赖性为线性。这是通过单光子和两光激发的单分子成像证实的，其中该图像在488 nm处激发，并且在370 nm之间检测到370和450 nm之间的图像与通常的单光激发图像非常相似。两光子抽象是以π-π*为中心的过渡。兴奋后，通过内部转换向 ^1MLCT状态传递能量，从发出短寿命的荧光。较少的