ACS Nano. 2014 Aug 26;8(8):8573-81. doi: 10.1021/nn503271k.
The time scales for interfacial charge separation and recombination play crucial roles in determining efficiencies of excitonic photovoltaics. Near-infrared photons are harvested efficiently by semiconducting single-walled carbon nanotubes (SWCNTs) paired with appropriate electron acceptors, such as fullerenes (e.g., C60). However, little is known about crucial photochemical events that occur on femtosecond to nanosecond time scales at such heterojunctions. Here, we present transient absorbance measurements that utilize a distinct spectroscopic signature of charges within SWCNTs, the absorbance of a trion quasiparticle, to measure both the ultrafast photoinduced electron transfer time (τpet) and yield (ϕpet) in photoexcited SWCNT–C60 bilayer films. The rise time of the trion-induced absorbance enables the determination of the photoinduced electron transfer (PET) time of τpet ≤ 120 fs, while an experimentally determined trion absorbance cross section reveals the yield of charge transfer (ϕpet ≈ 38 ± 3%). The extremely fast electron transfer times observed here are on par with some of the best donor:acceptor pairs in excitonic photovoltaics and underscore the potential for efficient energy harvesting in SWCNT-based devices.
界面电荷分离和复合的时间尺度在确定激子型光伏的效率方面起着至关重要的作用。通过与合适的电子受体（例如富勒烯（例如 C60））配对的半导体单壁碳纳米管（SWCNT）可以有效地收集近红外光子。然而，对于在这样的异质结上发生的飞秒到纳秒时间尺度的关键光化学事件，人们知之甚少。在这里，我们提出了瞬态吸收测量，该测量利用了 SWCNT 内电荷的独特光谱特征，即准粒子三重态的吸收，以测量光激发的 SWCNT-C60 双层膜中的超快光诱导电子转移时间（τpet）和产率（φpet）。准粒子诱导吸收的上升时间使我们能够确定光诱导电子转移（PET）时间τpet≤120fs，而实验确定的准粒子吸收截面则揭示了电荷转移的产率（φpet≈38±3％）。在这里观察到的极快电子转移时间与激子型光伏中一些最好的给体：受体对相当，这突显了基于 SWCNT 的器件中有效能量收集的潜力。
