Center for Nano Science and Technology @ Polimi, Istituto Italiano di Tecnologia, via G. Pascoli 70/3, 20133 Milano, Italy.
Phys Chem Chem Phys. 2011 Sep 7;13(33):15326-30. doi: 10.1039/c1cp21402k. Epub 2011 Jul 25.
Colloidal branched nanocrystals have been attracting increasing attention due to evidence of an interesting relationship between their complex shape and charge carrier dynamics. Herein, continuous wave photoinduced absorption (CW PIA) measurements of CdSe/CdS octapod-shaped nanocrystals are reported. CW PIA spectra show strong bleaching due to the one-dimensional (1D) CdS pod states (480 nm) and the zero-dimensional (0D) CdSe core states (690 nm). The agreement with previously reported ultrafast pump-probe experiments indicates that this strong bleaching signal may be assigned to state filling. Additional bleaching features at 520 and 560 nm are characterized by a longer lifetime and are thus ascribed to defect states, localized at the pod-core interface of the octapod, showing that some of the initially photogenerated carriers get quickly trapped into these long-lived defect states. However, we remark that a relevant part of electrons remain untrapped: this opens up the opportunity to exploit octapod shaped nanocrystals in photovoltaics applications, as electron acceptor materials, considering that several efficient hole extracting materials are already available for the realization of a composite bulk heterojunction.
由于复杂形状和载流子动力学之间存在有趣关系的证据，胶体支化纳米晶体引起了越来越多的关注。本文报道了 CdSe/CdS 八足形纳米晶体的连续波光致吸收（CW PIA）测量。CW PIA 光谱显示由于一维（1D）CdS 荚状态（480nm）和零维（0D）CdSe 核态（690nm）引起的强漂白。与先前报道的超快泵浦探测实验的一致性表明，这种强漂白信号可能归因于态填充。在 520nm 和 560nm 处的其他漂白特征具有更长的寿命，因此归因于缺陷态，定位于八足的荚-核界面，表明一些最初光生载流子很快被捕获到这些长寿命的缺陷态中。然而，我们注意到，一部分电子仍然未被捕获：这为在光伏应用中利用八足形纳米晶体作为电子受体材料开辟了机会，因为已经有几种高效的空穴提取材料可用于实现复合体异质结。
