Department of Chemical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
Nano Lett. 2017 Jun 14;17(6):3837-3843. doi: 10.1021/acs.nanolett.7b01237. Epub 2017 May 31.
Using liquid-liquid interfacial assembly, we control the deposition of CdSe nanoplatelets into face-down or edge-up configurations. Controlled assembly, combined with back focal plane imaging, enabled unambiguous determination of the transition dipole orientation. The transition dipole moment of the emissive band-edge exciton in CdSe nanoplatelets was found to be isotropically oriented within the plane of the nanoplatelet with no measurable out-of-plane component and no preference for the long- or short-axis of the nanoplatelet. Importantly, CdSe nanoplatelet films in the face-down configuration exhibited unity dipole orientation within the plane of the film, which could improve the external efficiency of nanoplatelet LEDs, lasers, photodetectors, and photovoltaic cells beyond that which is possible with isotropic emitters. We also show that the two self-assembled configurations have different Förster energy transfer rates, as a result of different dipole orientation and internanoplatelet distance.
利用液-液界面组装，我们控制 CdSe 纳米盘以面朝下或边缘朝上的方式沉积。通过控制组装并结合背焦面成像，可以明确确定跃迁偶极子取向。发现 CdSe 纳米盘的发射带边激子的跃迁偶极子在纳米盘平面内各向同性取向，没有可测量的面外分量，也没有对纳米盘的长轴或短轴的偏好。重要的是，面朝下配置的 CdSe 纳米盘薄膜在薄膜平面内具有一致的偶极子取向，这可以提高纳米盘 LED、激光器、光电探测器和光伏电池的外部效率，超过各向同性发射器的效率。我们还表明，由于不同的偶极子取向和纳米盘之间的距离，这两种自组装结构具有不同的Förster 能量转移速率。
