Ultrafast Formation of a Long-Lived Charge-Separated State in a Ru-Loaded Poly(3-hexylthiophene) Light-Harvesting Polymer

作者：Wang Li; Puodziukynaite Egle; Grumstrup Erik M; Brown Aaron C; Keinan Shahar; Schanze Kirk S; Reynolds John R; Papanikolas John M^*

来源：Journal of Physical Chemistry Letters, 2013, 4(14): 2269-2273.

DOI：10.1021/jz401089v

A light-harvesting macromolecular assembly (PT-Ru) consisting of a poly(3-hexylthiophene) (P3HT) scaffold and pendant Ru(II) polypyridyl complexes that exhibits rapid and efficient formation of a long-lived charge-separated state is described here. Photoinduced electron transfer from the polymer backbone to Ru(II) was investigated by femtosecond transient absorption spectroscopy. Photoexcitation at 388 nm results in the excitation of both the polymer backbone and Ru(II) complexes, with relative excitation probabilities of 60 and 40%, respectively. The dominant pathway (similar to 85%) for decay of the polymer excited state is direct electron transfer from the polymer scaffold to Ru(II), forming a positive polaron and a reduced complex [Ru-II(L)(2)(L-)](+), denoted Ru(I). The charge-separated state PT+center dot-Ru(I) is long-lived, persisting for 20-60 mu s, and is attributed to the high mobility of holes on the polymer backbone, which facilitates spatial separation of the electron and hole, delaying recombination. The remaining 15% of the polymer excited states undergo an alternate deactivation mechanism, possibly energy transfer to Ru(II), forming Ru(II)*.Ru(II)* formed by either direct excitation or energy transfer undergoes back energy transfer to the scaffold, forming the low-lying polymer triplet state on the nanosecond time scale.

• 出版日期2013-7-18