Cassette E, Pedetti S, Mahler B, Ithurria S, Dubertret B, Scholes G D
Department of Chemistry, Princeton University, Washington road, Princeton, New Jersey 08544, USA.
Phys Chem Chem Phys. 2017 Mar 28;19(12):8373-8379. doi: 10.1039/c6cp08689f. Epub 2017 Mar 10.
In this article we study the ultrafast dynamics of excitons and charge carriers photogenerated in two-dimensional in-plane heterostructures, namely, CdSe-CdTe nanoplatelets. We combine transient absorption and two-dimensional electronic spectroscopy to study charge transfer and delocalization from a few tens of femtoseconds to several nanoseconds. In contrast with spherical nanocrystals, the relative alignment of the electron and hole states of CdSe and CdTe in thin 2D nanoplatelets does not lead to a type-II heterostructure. Following the excitation in CdSe or CdTe materials, the electron preferentially delocalises instantaneously over the whole heterostructure. In addition, depending on the crown material (CdTe versus CdTeSe), the hole transfers either to trap states or to the crown, within a few hundreds of femtoseconds. We conclude that the photoluminescence band, at lower energy than the CdSe and CdTe first exciton transition, does not result from the recombination of the charge carriers at the charge transfer state but involves localised hole states.
在本文中，我们研究了二维平面异质结构（即CdSe-CdTe纳米片）中光生激子和电荷载流子的超快动力学。我们结合瞬态吸收和二维电子光谱来研究从几十飞秒到几纳秒的电荷转移和离域。与球形纳米晶体不同，二维薄纳米片中CdSe和CdTe的电子态和空穴态的相对排列不会导致II型异质结构。在CdSe或CdTe材料中激发后，电子优先在整个异质结构上瞬间离域。此外，根据冠层材料（CdTe与CdTeSe）的不同，空穴在几百飞秒内要么转移到陷阱态，要么转移到冠层。我们得出结论，能量低于CdSe和CdTe第一激子跃迁的光致发光带不是由电荷转移态处的电荷载流子复合产生的，而是涉及局域空穴态。
