Pace Natalie A, Arias Dylan H, Granger Devin B, Christensen Steven, Anthony John E, Johnson Justin C
National Renewable Energy Laboratory , Golden , CO 80401 , USA . Email:
Department of Chemistry and Biochemistry , University of Colorado , Boulder , CO 80309 , USA.
Chem Sci. 2018 Feb 26;9(11):3004-3013. doi: 10.1039/c7sc04688j. eCollection 2018 Mar 21.
We employ a combination of linear spectroscopy, electrochemistry, and transient absorption spectroscopy to characterize the interplay between electron transfer and singlet fission dynamics in polyacene-based dyes attached to nanostructured TiO. For triisopropyl silylethynyl (TIPS)-pentacene, we find that the singlet fission time constant increases to 6.5 ps on a nanostructured TiO surface relative to a thin film time constant of 150 fs, and that triplets do not dissociate after they are formed. In contrast, TIPS-tetracene singlets quickly dissociate in 2 ps at the molecule/TiO interface, and this dissociation outcompetes the relatively slow singlet fission process. The addition of an alumina layer slows down electron injection, allowing the formation of triplets from singlet fission in 40 ps. However, the triplets do not inject electrons, which is likely due to a lack of sufficient driving force for triplet dissociation. These results point to the critical balance required between efficient singlet fission and appropriate energetics for interfacial charge transfer.
我们采用线性光谱、电化学和瞬态吸收光谱相结合的方法，来表征附着在纳米结构TiO上的并苯类染料中电子转移与单线态裂变动力学之间的相互作用。对于三异丙基甲硅烷基乙炔基（TIPS）-并五苯，我们发现，相对于150飞秒的薄膜时间常数，其在纳米结构TiO表面的单线态裂变时间常数增加到了6.5皮秒，并且三线态形成后不会解离。相比之下，TIPS-并四苯单线态在分子/TiO界面处以2皮秒的速度迅速解离，这种解离超过了相对较慢的单线态裂变过程。氧化铝层的添加减缓了电子注入，使得单线态裂变在40皮秒内形成三线态。然而，三线态不会注入电子，这可能是由于缺乏足够的驱动力来实现三线态解离。这些结果表明，在高效单线态裂变与界面电荷转移的适当能量之间需要达到关键平衡。
